Pub Date : 2024-06-21DOI: 10.1103/physrevx.14.021051
Yanyu Jia, Guo Yu, Tiancheng Song, Fang Yuan, Ayelet J. Uzan, Yue Tang, Pengjie Wang, Ratnadwip Singha, Michael Onyszczak, Zhaoyi Joy Zheng, Kenji Watanabe, Takashi Taniguchi, Leslie M. Schoop, Sanfeng Wu
Two-dimensional (2D) transition metal dichalcogenides (TMDs) is a versatile class of quantum materials of interest to various fields including, e.g., nanoelectronics, optical devices, and topological and correlated quantum matter. Tailoring the electronic properties of TMDs is essential to their applications in many directions. Here, we report that a highly controllable and uniform on-chip 2D metallization process converts a class of atomically thin TMDs into robust superconductors, a property belonging to none of the starting materials. As examples, we demonstrate the introduction of superconductivity into a class of 2D air-sensitive topological TMDs, including monolayers of , , and , as well as their natural and twisted bilayers, metallized with an ultrathin layer of palladium. This class of TMDs is known to exhibit intriguing topological phases ranging from topological insulator, Weyl semimetal to fractional Chern insulator. The unique, high-quality two-dimensional metallization process is based on our recent findings of the long-distance, non-Fickian in-plane mass transport and chemistry in 2D that occur at relatively low temperatures and in devices fully encapsulated with inert insulating layers. Highly compatible with existing nanofabrication techniques for van der Waals stacks, our results offer a route to designing and engineering superconductivity and topological phases in a class of correlated 2D materials.
{"title":"Superconductivity from On-Chip Metallization on 2D Topological Chalcogenides","authors":"Yanyu Jia, Guo Yu, Tiancheng Song, Fang Yuan, Ayelet J. Uzan, Yue Tang, Pengjie Wang, Ratnadwip Singha, Michael Onyszczak, Zhaoyi Joy Zheng, Kenji Watanabe, Takashi Taniguchi, Leslie M. Schoop, Sanfeng Wu","doi":"10.1103/physrevx.14.021051","DOIUrl":"https://doi.org/10.1103/physrevx.14.021051","url":null,"abstract":"Two-dimensional (2D) transition metal dichalcogenides (TMDs) is a versatile class of quantum materials of interest to various fields including, e.g., nanoelectronics, optical devices, and topological and correlated quantum matter. Tailoring the electronic properties of TMDs is essential to their applications in many directions. Here, we report that a highly controllable and uniform on-chip 2D metallization process converts a class of atomically thin TMDs into robust superconductors, a property belonging to none of the starting materials. As examples, we demonstrate the introduction of superconductivity into a class of 2D air-sensitive topological TMDs, including monolayers of <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mrow><mi mathvariant=\"normal\">T</mi></mrow><mrow><mi mathvariant=\"normal\">d</mi></mrow></msub><mtext>−</mtext><msub><mrow><mi>WTe</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math>, <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>1</mn><msup><mrow><mi mathvariant=\"normal\">T</mi></mrow><mrow><mo>′</mo></mrow></msup><mtext>−</mtext><msub><mrow><mi>MoTe</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math>, and <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>2</mn><mi mathvariant=\"normal\">H</mi><mtext>−</mtext><msub><mrow><mi>MoTe</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math>, as well as their natural and twisted bilayers, metallized with an ultrathin layer of palladium. This class of TMDs is known to exhibit intriguing topological phases ranging from topological insulator, Weyl semimetal to fractional Chern insulator. The unique, high-quality two-dimensional metallization process is based on our recent findings of the long-distance, non-Fickian in-plane mass transport and chemistry in 2D that occur at relatively low temperatures and in devices fully encapsulated with inert insulating layers. Highly compatible with existing nanofabrication techniques for van der Waals stacks, our results offer a route to designing and engineering superconductivity and topological phases in a class of correlated 2D materials.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":null,"pages":null},"PeriodicalIF":12.5,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141435809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-20DOI: 10.1103/physrevx.14.021049
Konrad Viebahn, Anne-Sophie Walter, Eric Bertok, Zijie Zhu, Marius Gächter, Armando A. Aligia, Fabian Heidrich-Meisner, Tilman Esslinger
A topological “Thouless” pump represents the quantized motion of particles in response to a slow, cyclic modulation of external control parameters. The Thouless pump, like the quantum Hall effect, is of fundamental interest in physics, because it links physically measurable quantities, such as particle currents, to geometric properties of the experimental system, which can be robust against perturbations and, thus, technologically useful. So far, experiments probing the interplay between topology and interparticle interactions have remained relatively scarce. Here, we observe a Thouless-type charge pump in which the particle current and its directionality inherently rely on the presence of strong interactions. Experimentally, we utilize a two-component Fermi gas in a dynamical superlattice which does not exhibit a sliding motion and remains trivial in the single-particle regime. However, when tuning interparticle interactions from zero to positive values, the system undergoes a transition from being stationary to drifting in one direction, consistent with quantized pumping in the first cycle. Remarkably, the topology of the interacting pump trajectory cannot be adiabatically connected to a noninteracting limit, highlighted by the fact that only one atom is transferred per cycle. Our experiments suggest that Thouless charge pumps are promising platforms to gain insights into interaction-driven topological transitions and topological quantum matter.
{"title":"Interactions Enable Thouless Pumping in a Nonsliding Lattice","authors":"Konrad Viebahn, Anne-Sophie Walter, Eric Bertok, Zijie Zhu, Marius Gächter, Armando A. Aligia, Fabian Heidrich-Meisner, Tilman Esslinger","doi":"10.1103/physrevx.14.021049","DOIUrl":"https://doi.org/10.1103/physrevx.14.021049","url":null,"abstract":"A topological “Thouless” pump represents the quantized motion of particles in response to a slow, cyclic modulation of external control parameters. The Thouless pump, like the quantum Hall effect, is of fundamental interest in physics, because it links physically measurable quantities, such as particle currents, to geometric properties of the experimental system, which can be robust against perturbations and, thus, technologically useful. So far, experiments probing the interplay between topology and interparticle interactions have remained relatively scarce. Here, we observe a Thouless-type charge pump in which the particle current and its directionality inherently rely on the presence of strong interactions. Experimentally, we utilize a two-component Fermi gas in a dynamical superlattice which does not exhibit a sliding motion and remains trivial in the single-particle regime. However, when tuning interparticle interactions from zero to positive values, the system undergoes a transition from being stationary to drifting in one direction, consistent with quantized pumping in the first cycle. Remarkably, the topology of the interacting pump trajectory cannot be adiabatically connected to a noninteracting limit, highlighted by the fact that only one atom is transferred per cycle. Our experiments suggest that Thouless charge pumps are promising platforms to gain insights into interaction-driven topological transitions and topological quantum matter.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":null,"pages":null},"PeriodicalIF":12.5,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141435798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Quantum many-body systems, particularly, the ones with large near- density states, are well known for exhibiting rich phase diagrams as a result of enhanced electron correlations. The recently discovered locally noncentrosymmetric heavy fermion superconductor has stimulated extensive attention due to its unusual phase diagram consisting of two-phase superconductivity, antiferromagnetic order, and possible quadrupole-density wave orders. However, the critical near- electronic structure remains experimentally elusive. Here, we provide this key information by combining soft-x-ray and vacuum ultraviolet (VUV) angle-resolved-photoemission-spectroscopy measurements and atom-resolved density-functional-theory calculations. With bulk-sensitive soft x ray, we reveal quasi-2D hole and electron pockets near the . On the other hand, under VUV light, the Ce flat bands are resolved with the hybridization persisting up to well above the Kondo temperature. Most importantly, we observe a symmetry-protected fourfold Van Hove singularity (VHS) coexisting with the flat bands at the point, which, to the best of our knowledge, has never been reported before. Such a rare coexistence is expected to lead to a large density of states at the zone edge, a large upper critical field of the odd-parity phase, as well as spin and/or charge instabilities with a vector of (, , 0). Uniquely, it will also result in a new
众所周知，量子多体系统，尤其是具有大的近 EF 密度态的量子多体系统，由于电子相关性的增强而表现出丰富的相图。最近发现的局部非中心对称重费米子超导体 CeRh2As2 因其不同寻常的 H-T 相图（包括两相超导性、反铁磁秩序和可能的四极密度波秩序）而引起了广泛关注。然而，临界近 EF 电子结构在实验中仍然难以捉摸。在这里，我们将软 X 射线和真空紫外线（VUV）角度分辨光电发射光谱测量与原子分辨密度函数理论（DFT）+U 计算相结合，提供了这一关键信息。通过体敏软 X 射线，我们揭示了 EF 附近的准二维空穴和电子袋。另一方面，在紫外光下，Ce 平带被解析，c-f 杂化持续到远远高于 Kondo 温度。最重要的是，我们在 X 点观察到一个对称保护的四倍范霍夫奇点（VHS）与铈 4f5/21 平面带共存，据我们所知，这是以前从未报道过的。这种罕见的共存现象预计会导致区域边缘的大状态密度、奇偶相的大上临界场以及矢量为（1/2, 1/2, 0）的自旋和/或电荷不稳定性。独特的是，它还会导致一种新型的 f-VHS 杂化，改变 VHS 和平面带的有序和精细电子结构。我们的发现不仅为了解 CeRh2As2 中多相的性质提供了重要见解，而且为探索具有 f-VHS 杂化的多体系统的新特性开辟了新的前景。
{"title":"Coexistence of near-EF Flat Band and Van Hove Singularity in a Two-Phase Superconductor","authors":"Xuezhi Chen, Le Wang, Jun Ishizuka, Renjie Zhang, Kosuke Nogaki, Yiwei Cheng, Fazhi Yang, Zhenhua Chen, Fangyuan Zhu, Zhengtai Liu, Jiawei Mei, Youichi Yanase, Baiqing Lv, Yaobo Huang","doi":"10.1103/physrevx.14.021048","DOIUrl":"https://doi.org/10.1103/physrevx.14.021048","url":null,"abstract":"Quantum many-body systems, particularly, the ones with large near-<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mrow><mi>E</mi></mrow><mrow><mi>F</mi></mrow></msub></mrow></math> density states, are well known for exhibiting rich phase diagrams as a result of enhanced electron correlations. The recently discovered locally noncentrosymmetric heavy fermion superconductor <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>CeRh</mi><mn>2</mn></msub><msub><mi>As</mi><mn>2</mn></msub></mrow></math> has stimulated extensive attention due to its unusual <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>H</mi><mtext>−</mtext><mi>T</mi></mrow></math> phase diagram consisting of two-phase superconductivity, antiferromagnetic order, and possible quadrupole-density wave orders. However, the critical near-<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mrow><mi>E</mi></mrow><mrow><mi>F</mi></mrow></msub></mrow></math> electronic structure remains experimentally elusive. Here, we provide this key information by combining soft-x-ray and vacuum ultraviolet (VUV) angle-resolved-photoemission-spectroscopy measurements and atom-resolved density-functional-theory <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo stretchy=\"false\">(</mo><mi>DFT</mi><mo stretchy=\"false\">)</mo><mo>+</mo><mi>U</mi></mrow></math> calculations. With bulk-sensitive soft x ray, we reveal quasi-2D hole and electron pockets near the <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mrow><mi>E</mi></mrow><mrow><mi>F</mi></mrow></msub></mrow></math>. On the other hand, under VUV light, the Ce flat bands are resolved with the <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>c</mi><mtext>−</mtext><mi>f</mi></mrow></math> hybridization persisting up to well above the Kondo temperature. Most importantly, we observe a symmetry-protected fourfold Van Hove singularity (VHS) coexisting with the <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Ce</mi><mtext> </mtext><mtext> </mtext><mtext> </mtext><mn>4</mn><msubsup><mrow><mi>f</mi></mrow><mrow><mn>5</mn><mo>/</mo><mn>2</mn></mrow><mrow><mn>1</mn></mrow></msubsup></mrow></math> flat bands at the <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>X</mi></math> point, which, to the best of our knowledge, has never been reported before. Such a rare coexistence is expected to lead to a large density of states at the zone edge, a large upper critical field of the odd-parity phase, as well as spin and/or charge instabilities with a vector of (<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math>, <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math>, 0). Uniquely, it will also result in a new ","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":null,"pages":null},"PeriodicalIF":12.5,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141435772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-18DOI: 10.1103/physrevx.14.021047
Yuelin Shao, Xi Dai
We propose a new electrical breakdown mechanism for exciton insulators in the BCS limit, which differs fundamentally from the Zener breakdown mechanism observed in traditional band insulators. Our new mechanism results from the instability of the many-body ground state for exciton condensation, caused by the strong competition between the polarization and condensation energies in the presence of an electric field. We refer to this mechanism as “many-body breakdown.” To investigate this new mechanism, we propose a BCS-type trial wave function under finite electric fields and use it to study the many-body breakdown numerically. Our results reveal two different types of electric breakdown behavior. If the system size is larger than a critical value, the Zener tunneling process is first turned on when an electrical field is applied, but the excitonic gap remains until the field strength reaches the critical value of the many-body breakdown, after which the excitonic gap disappears and the system becomes a highly conductive metallic state. However, if the system size is much smaller than the critical value, the intermediate tunneling phase disappears since the many-body breakdown happens before the onset of Zener tunneling. The sudden disappearance of the local gap leads to an “off-on” feature in the current-voltage () curve, providing a straightforward way to distinguish excitonic insulators from normal insulators.
{"title":"Electrical Breakdown of Excitonic Insulators","authors":"Yuelin Shao, Xi Dai","doi":"10.1103/physrevx.14.021047","DOIUrl":"https://doi.org/10.1103/physrevx.14.021047","url":null,"abstract":"We propose a new electrical breakdown mechanism for exciton insulators in the BCS limit, which differs fundamentally from the Zener breakdown mechanism observed in traditional band insulators. Our new mechanism results from the instability of the many-body ground state for exciton condensation, caused by the strong competition between the polarization and condensation energies in the presence of an electric field. We refer to this mechanism as “many-body breakdown.” To investigate this new mechanism, we propose a BCS-type trial wave function under finite electric fields and use it to study the many-body breakdown numerically. Our results reveal two different types of electric breakdown behavior. If the system size is larger than a critical value, the Zener tunneling process is first turned on when an electrical field is applied, but the excitonic gap remains until the field strength reaches the critical value of the many-body breakdown, after which the excitonic gap disappears and the system becomes a highly conductive metallic state. However, if the system size is much smaller than the critical value, the intermediate tunneling phase disappears since the many-body breakdown happens before the onset of Zener tunneling. The sudden disappearance of the local gap leads to an “off-on” feature in the current-voltage (<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>I</mi><mtext>−</mtext><mi>V</mi></mrow></math>) curve, providing a straightforward way to distinguish excitonic insulators from normal insulators.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":null,"pages":null},"PeriodicalIF":12.5,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141425174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-17DOI: 10.1103/physrevx.14.021046
Soumya Sankar, Ruizi Liu, Cheng-Ping Zhang, Qi-Fang Li, Caiyun Chen, Xue-Jian Gao, Jiangchang Zheng, Yi-Hsin Lin, Kun Qian, Ruo-Peng Yu, Xu Zhang, Zi Yang Meng, Kam Tuen Law, Qiming Shao, Berthold Jäck
Berry curvature multipoles appearing in topological quantum materials have recently attracted much attention. Their presence can manifest in novel phenomena, such as nonlinear anomalous Hall effects (NLAHE). The notion of Berry curvature multipoles extends our understanding of Berry curvature effects on the material properties. Hence, research on this subject is of fundamental importance and may also enable future applications in energy harvesting and high-frequency technology. It was shown that a Berry curvature dipole can give rise to a second-order NLAHE in materials of low crystalline symmetry. Here, we demonstrate a fundamentally new mechanism for Berry curvature multipoles in antiferromagnets that are supported by the underlying magnetic symmetries. Carrying out electric transport measurements on the kagome antiferromagnet FeSn, we observe a third-order NLAHE, which appears as a transverse voltage response at the third harmonic frequency when a longitudinal ac drive is applied. Interestingly, this NLAHE is strongest at and above room temperature. We combine these measurements with a scaling law analysis, a symmetry analysis, model calculations, first-principle calculations, and magnetic Monte Carlo simulations to show that the observed NLAHE is induced by a Berry curvature quadrupole appearing in the spin-canted state of FeSn. At a practical level, our study establishes NLAHE as a sensitive probe of antiferromagnetic phase transitions in other materials—such as moiré superlattices, two-dimensional van der Waal magnets, and quantum spin liquid candidates, which remain poorly understood to date. More broadly, Berry curvature multipole effects are predicted to exist for 90 magnetic point groups. Hence, our work opens a new research area to study a variety of topological magnetic materials through nonlinear measurement protocols.
{"title":"Experimental Evidence for a Berry Curvature Quadrupole in an Antiferromagnet","authors":"Soumya Sankar, Ruizi Liu, Cheng-Ping Zhang, Qi-Fang Li, Caiyun Chen, Xue-Jian Gao, Jiangchang Zheng, Yi-Hsin Lin, Kun Qian, Ruo-Peng Yu, Xu Zhang, Zi Yang Meng, Kam Tuen Law, Qiming Shao, Berthold Jäck","doi":"10.1103/physrevx.14.021046","DOIUrl":"https://doi.org/10.1103/physrevx.14.021046","url":null,"abstract":"Berry curvature multipoles appearing in topological quantum materials have recently attracted much attention. Their presence can manifest in novel phenomena, such as nonlinear anomalous Hall effects (NLAHE). The notion of Berry curvature multipoles extends our understanding of Berry curvature effects on the material properties. Hence, research on this subject is of fundamental importance and may also enable future applications in energy harvesting and high-frequency technology. It was shown that a Berry curvature dipole can give rise to a second-order NLAHE in materials of low crystalline symmetry. Here, we demonstrate a fundamentally new mechanism for Berry curvature multipoles in antiferromagnets that are supported by the underlying magnetic symmetries. Carrying out electric transport measurements on the kagome antiferromagnet FeSn, we observe a third-order NLAHE, which appears as a transverse voltage response at the third harmonic frequency when a longitudinal ac drive is applied. Interestingly, this NLAHE is strongest at and above room temperature. We combine these measurements with a scaling law analysis, a symmetry analysis, model calculations, first-principle calculations, and magnetic Monte Carlo simulations to show that the observed NLAHE is induced by a Berry curvature quadrupole appearing in the spin-canted state of FeSn. At a practical level, our study establishes NLAHE as a sensitive probe of antiferromagnetic phase transitions in other materials—such as moiré superlattices, two-dimensional van der Waal magnets, and quantum spin liquid candidates, which remain poorly understood to date. More broadly, Berry curvature multipole effects are predicted to exist for 90 magnetic point groups. Hence, our work opens a new research area to study a variety of topological magnetic materials through nonlinear measurement protocols.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":null,"pages":null},"PeriodicalIF":12.5,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141333699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-14DOI: 10.1103/physrevx.14.021045
Mengyao Du, Huiqian Min, Ke Xia, Dazhi Hou, Lei Wang, Zhiyong Qiu
Spin current is a crucial element in spintronics, and its diffusion in materials is typically characterized by monotonic decay. However, when the material hosting the spin current is also a magnet, the spin current is expected to exhibit spatial oscillations, the observation of which remains elusive. Here, we demonstrate the spatial oscillation of a spin current in a nickel film by measuring the thickness-dependent inverse spin Hall effect in bilayers. The inverse spin Hall current in nickel is found to oscillate with its film thickness, in contrast to nonmagnetic materials, and that the oscillation period quantitatively agrees with theoretical predictions based on differences in the Fermi wave vector between majority and minority carriers. Our findings reveal a previously hidden behavior of spin-transport dynamics and identify a new degree of freedom for manipulating spin current, with potential implications for future spintronic devices.
{"title":"Direct Observation of Spin Current Oscillation in a Ferromagnet","authors":"Mengyao Du, Huiqian Min, Ke Xia, Dazhi Hou, Lei Wang, Zhiyong Qiu","doi":"10.1103/physrevx.14.021045","DOIUrl":"https://doi.org/10.1103/physrevx.14.021045","url":null,"abstract":"Spin current is a crucial element in spintronics, and its diffusion in materials is typically characterized by monotonic decay. However, when the material hosting the spin current is also a magnet, the spin current is expected to exhibit spatial oscillations, the observation of which remains elusive. Here, we demonstrate the spatial oscillation of a spin current in a nickel film by measuring the thickness-dependent inverse spin Hall effect in <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Ni</mi><mo>/</mo><mi>YIG</mi></mrow></math> bilayers. The inverse spin Hall current in nickel is found to oscillate with its film thickness, in contrast to nonmagnetic materials, and that the oscillation period quantitatively agrees with theoretical predictions based on differences in the Fermi wave vector between majority and minority carriers. Our findings reveal a previously hidden behavior of spin-transport dynamics and identify a new degree of freedom for manipulating spin current, with potential implications for future spintronic devices.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":null,"pages":null},"PeriodicalIF":12.5,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141326841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-13DOI: 10.1103/physrevx.14.021044
Zheng Zhou (周正), Liangdong Hu, W. Zhu, Yin-Chen He
The deconfined quantum critical point (DQCP) is an example of phase transitions beyond the Landau symmetry-breaking paradigm that attracts wide interest. However, its nature has not been settled after decades of study. In this paper, we apply the recently proposed fuzzy-sphere regularization to study the SO(5) nonlinear sigma model with a topological Wess-Zumino-Witten term, which serves as a dual description of the DQCP with an exact SO(5) symmetry. We demonstrate that the fuzzy sphere functions as a powerful microscope, magnifying and revealing a wealth of crucial information about the DQCP, ultimately paving the way toward its final answer. In particular, through exact diagonalization, we provide clear evidence that the DQCP exhibits approximate conformal symmetry. The evidence includes the existence of a conserved SO(5) symmetry current, a stress tensor, and integer-spaced levels between conformal primaries and their descendants. Most remarkably, we identify 23 primaries and 76 conformal descendants. Furthermore, by examining the renormalization group flow of the lowest symmetry singlet as well as other primaries, we provide numerical evidence in favor of DQCP being pseudo-critical, with the approximate conformal symmetry plausibly emerging from nearby complex fixed points. The primary spectrum we compute also has important implications, including the conclusion that the SO(5) DQCP cannot describe a direct transition from the Néel to valence bond solid phase on the honeycomb lattice.
{"title":"SO(5) Deconfined Phase Transition under the Fuzzy-Sphere Microscope: Approximate Conformal Symmetry, Pseudo-Criticality, and Operator Spectrum","authors":"Zheng Zhou (周正), Liangdong Hu, W. Zhu, Yin-Chen He","doi":"10.1103/physrevx.14.021044","DOIUrl":"https://doi.org/10.1103/physrevx.14.021044","url":null,"abstract":"The deconfined quantum critical point (DQCP) is an example of phase transitions beyond the Landau symmetry-breaking paradigm that attracts wide interest. However, its nature has not been settled after decades of study. In this paper, we apply the recently proposed fuzzy-sphere regularization to study the SO(5) nonlinear sigma model with a topological Wess-Zumino-Witten term, which serves as a dual description of the DQCP with an exact SO(5) symmetry. We demonstrate that the fuzzy sphere functions as a powerful microscope, magnifying and revealing a wealth of crucial information about the DQCP, ultimately paving the way toward its final answer. In particular, through exact diagonalization, we provide clear evidence that the DQCP exhibits approximate conformal symmetry. The evidence includes the existence of a conserved SO(5) symmetry current, a stress tensor, and integer-spaced levels between conformal primaries and their descendants. Most remarkably, we identify 23 primaries and 76 conformal descendants. Furthermore, by examining the renormalization group flow of the lowest symmetry singlet as well as other primaries, we provide numerical evidence in favor of DQCP being pseudo-critical, with the approximate conformal symmetry plausibly emerging from nearby complex fixed points. The primary spectrum we compute also has important implications, including the conclusion that the SO(5) DQCP cannot describe a direct transition from the Néel to valence bond solid phase on the honeycomb lattice.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":null,"pages":null},"PeriodicalIF":12.5,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141319992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-11DOI: 10.1103/physrevx.14.021043
Y.-F. Li, S.-D. Chen, M. García-Díez, M. I. Iraola, H. Pfau, Y.-L. Zhu, Z.-Q. Mao, T. Chen, M. Yi, P.-C. Dai, J. A. Sobota, M. Hashimoto, M. G. Vergniory, D.-H. Lu, Z.-X. Shen
(FTS) occupies a special spot in modern condensed matter physics at the intersections of electron correlation, topology, and unconventional superconductivity. The bulk electronic structure of FTS is predicted to be topologically nontrivial due to the band inversion between the and bands along . However, there remain debates in both the authenticity of the Dirac surface states (DSSs) and the experimental deviations of band structure from the theoretical band inversion picture. Here we resolve these debates through a comprehensive angle-resolved photoemission spectroscopy investigation. We first observe a persistent DSS independent of . Then, by comparing FTS with FeSe, which has no band inversion along , we identify the spectral weight fingerprint of both the presence of the band and the inversion between the and bands. Furthermore, we propose a renormalization scheme for the band structure under the framework of a tight-binding model preserving crystal symmetry. Our results highlight the significant influence of correlation on modifying the band structure and make a strong case for the existence of topological band structure in this unconventional superconductor.
{"title":"Orbital Ingredients and Persistent Dirac Surface State for the Topological Band Structure in FeTe0.55Se0.45","authors":"Y.-F. Li, S.-D. Chen, M. García-Díez, M. I. Iraola, H. Pfau, Y.-L. Zhu, Z.-Q. Mao, T. Chen, M. Yi, P.-C. Dai, J. A. Sobota, M. Hashimoto, M. G. Vergniory, D.-H. Lu, Z.-X. Shen","doi":"10.1103/physrevx.14.021043","DOIUrl":"https://doi.org/10.1103/physrevx.14.021043","url":null,"abstract":"<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>FeTe</mi><mn>0.55</mn></msub><mrow><msub><mrow><mi>Se</mi></mrow><mrow><mn>0.45</mn></mrow></msub></mrow></math> (FTS) occupies a special spot in modern condensed matter physics at the intersections of electron correlation, topology, and unconventional superconductivity. The bulk electronic structure of FTS is predicted to be topologically nontrivial due to the band inversion between the <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>d</mi><mrow><mi>x</mi><mi>z</mi></mrow></msub></math> and <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>p</mi><mi>z</mi></msub></math> bands along <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">Γ</mi><mtext>−</mtext><mi>Z</mi></mrow></math>. However, there remain debates in both the authenticity of the Dirac surface states (DSSs) and the experimental deviations of band structure from the theoretical band inversion picture. Here we resolve these debates through a comprehensive angle-resolved photoemission spectroscopy investigation. We first observe a persistent DSS independent of <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>k</mi><mi>z</mi></msub></math>. Then, by comparing FTS with FeSe, which has no band inversion along <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">Γ</mi><mtext>−</mtext><mi>Z</mi></mrow></math>, we identify the spectral weight fingerprint of both the presence of the <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>p</mi><mi>z</mi></msub></math> band and the inversion between the <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>d</mi><mrow><mi>x</mi><mi>z</mi></mrow></msub></math> and <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>p</mi><mi>z</mi></msub></math> bands. Furthermore, we propose a renormalization scheme for the band structure under the framework of a tight-binding model preserving crystal symmetry. Our results highlight the significant influence of correlation on modifying the band structure and make a strong case for the existence of topological band structure in this unconventional superconductor.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":null,"pages":null},"PeriodicalIF":12.5,"publicationDate":"2024-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141309036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-10DOI: 10.1103/physrevx.14.021042
Xiaoyu Wang, Oskar Vafek
Magic-angle twisted bilayer graphene is the best-studied physical platform featuring moiré potential-induced narrow bands with nontrivial topology and strong electronic correlations. Despite their significance, the Chern insulating states observed at a finite magnetic field—and extrapolating to a band filling at zero field—remain poorly understood. Unraveling their nature is among the most important open problems in the province of moiré materials. Here, we present the first comprehensive study of interacting electrons in finite magnetic field while varying the electron density, twist angle, and heterostrain. Within a panoply of correlated Chern phases emerging at a range of twist angles, we uncover a unified description for the ubiquitous sequence of states with the Chern number for , , , and . We also find correlated Chern insulators at unconventional sequences with , as well as with fractional , and elucidate their nature.
魔角扭曲双层石墨烯是研究得最透彻的物理平台，其特点是摩尔势诱导的窄带具有非难拓扑和强电子相关性。尽管其重要性不言而喻，但在有限磁场下观察到的切尔诺绝缘态--推断为零磁场下的带填充态--仍然鲜为人知。揭示其本质是摩尔材料领域最重要的未决问题之一。在此，我们首次对有限磁场中的相互作用电子进行了全面研究，同时改变了电子密度、扭转角和异应变。在扭转角范围内出现的一系列相关切尔恩相中，我们发现了一个统一的描述，即在(s,t)=±(0,4)、±(1,3)、±(2,2)和±(3,1)时，切尔恩数为 t 的无处不在的状态序列。我们还在 s+t≠±4 以及分数 s 的非常规序列中发现了相关的切尔诺绝缘体，并阐明了它们的性质。
{"title":"Theory of Correlated Chern Insulators in Twisted Bilayer Graphene","authors":"Xiaoyu Wang, Oskar Vafek","doi":"10.1103/physrevx.14.021042","DOIUrl":"https://doi.org/10.1103/physrevx.14.021042","url":null,"abstract":"Magic-angle twisted bilayer graphene is the best-studied physical platform featuring moiré potential-induced narrow bands with nontrivial topology and strong electronic correlations. Despite their significance, the Chern insulating states observed at a finite magnetic field—and extrapolating to a band filling <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>s</mi></math> at zero field—remain poorly understood. Unraveling their nature is among the most important open problems in the province of moiré materials. Here, we present the first comprehensive study of interacting electrons in finite magnetic field while varying the electron density, twist angle, and heterostrain. Within a panoply of correlated Chern phases emerging at a range of twist angles, we uncover a unified description for the ubiquitous sequence of states with the Chern number <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>t</mi></math> for <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo stretchy=\"false\">(</mo><mi>s</mi><mo>,</mo><mi>t</mi><mo stretchy=\"false\">)</mo><mo>=</mo><mo>±</mo><mo stretchy=\"false\">(</mo><mn>0</mn><mo>,</mo><mn>4</mn><mo stretchy=\"false\">)</mo></math>, <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>±</mo><mo stretchy=\"false\">(</mo><mn>1</mn><mo>,</mo><mn>3</mn><mo stretchy=\"false\">)</mo></math>, <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>±</mo><mo stretchy=\"false\">(</mo><mn>2</mn><mo>,</mo><mn>2</mn><mo stretchy=\"false\">)</mo></math>, and <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>±</mo><mo stretchy=\"false\">(</mo><mn>3</mn><mo>,</mo><mn>1</mn><mo stretchy=\"false\">)</mo></math>. We also find correlated Chern insulators at unconventional sequences with <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>s</mi><mo>+</mo><mi>t</mi><mo>≠</mo><mo>±</mo><mn>4</mn></math>, as well as with fractional <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>s</mi></math>, and elucidate their nature.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":null,"pages":null},"PeriodicalIF":12.5,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141304546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-10DOI: 10.1103/physrevx.14.021041
Malte Brammerloh, Renat Sibgatulin, Karl-Heinz Herrmann, Markus Morawski, Tilo Reinert, Carsten Jäger, Roland Müller, Gerald Falkenberg, Dennis Brückner, Kerrin J. Pine, Andreas Deistung, Valerij G. Kiselev, Jürgen R. Reichenbach, Nikolaus Weiskopf, Evgeniya Kirilina
Paramagnetic transition metals play a crucial role as cofactors in various cellular catalytic processes. However, their high concentrations in reactive oxidation states can induce oxidative stress, resulting in cell dysfunction or death. Hence, it is vital to have methods to monitor metal concentrations and paramagnetic properties in cells for medicine and cell biology. Here we present a novel multimodal method for in-cell magnetometry enabling direct measurement of metal magnetic properties within individual cells in tissue, without prior isolation and at room temperature. Individual cell magnetic moments are measured using superresolution magnetic resonance imaging (MRI) microscopy at 9.4 T by detecting microscopic magnetic-field perturbations around the cells. The cellular metal content is quantified using ion-beam microscopy or synchrotron micro-x-ray fluorescence for the same cells. The metal magnetic susceptibility at 9.4 T is then obtained from the slope of the cell magnetic moments’ dependence on cell metal content. To estimate the susceptibility at lower fields, multifield MR relaxometry and biophysical modeling are employed, extrapolating the 9.4-T susceptibility values to fields as low as 3 T. We apply the new method to determine the susceptibility of iron accumulated in human dopaminergic neurons inside neuromelanin, the by-product of dopamine synthesis. The susceptibility of iron in neuromelanin is measured to be providing unique insights into the biochemistry of iron inside dopaminergic neurons. The obtained value reveals a predominant monoatomic low-affinity iron-binding site within neuromelanin, indicating a higher neurotoxicity of iron than previously suggested. Furthermore, the measured susceptibility value establishes a quantitative relationship between cellular iron concentration and iron-sensitive MRI parameters, which can be noninvasively measured in vivo. This breakthrough paves the way for the in vivo detection of dopaminergic neuron density and iron load, requiring a standard clinical MRI scanner only. It promises to facilitate early diagnosis of Parkinson’s disease. In conclusion, our presented novel method enables the direct measurements of magnetic properties of paramagnetic metals within single cells with high sensitivity and across large cell groups within a macroscopic volume, providing invaluable information about the cellular biology of metals.
顺磁性过渡金属在各种细胞催化过程中作为辅助因子发挥着至关重要的作用。然而，它们在反应性氧化状态下的高浓度会诱发氧化应激，导致细胞功能障碍或死亡。因此，拥有监测细胞中金属浓度和顺磁性能的方法对于医学和细胞生物学来说至关重要。在这里，我们提出了一种新颖的多模式细胞内磁力测量方法，无需事先分离，可在室温下直接测量组织中单个细胞内的金属磁性。通过检测细胞周围的微观磁场扰动，在 9.4 T 下使用超分辨率磁共振成像（MRI）显微镜测量单个细胞的磁矩。使用离子束显微镜或同步加速器微 X 射线荧光对相同细胞的细胞金属含量进行量化。然后根据细胞磁矩与细胞金属含量的斜率关系得出 9.4 T 时的金属磁感应强度。为了估算较低磁场下的磁感应强度，我们采用了多场磁共振弛豫测量法和生物物理模型，将 9.4 T 的磁感应强度值外推至低至 3 T 的磁场。测得神经络氨酸中铁的易感性为χρ=(2.98±0.19)×10-6 m3/kg，为了解多巴胺能神经元内铁的生物化学提供了独特的见解。所获得的值揭示了神经髓鞘内一个主要的单原子低亲和性铁结合位点，表明铁的神经毒性比以前认为的要高。此外，所测得的易感度值还确定了细胞铁浓度与铁敏感磁共振成像参数之间的定量关系，这种关系可以在体内进行无创测量。这一突破为在体内检测多巴胺能神经元密度和铁负荷铺平了道路，只需要一台标准的临床磁共振成像扫描仪。它有望促进帕金森病的早期诊断。总之，我们提出的新方法能够以高灵敏度直接测量单细胞内顺磁性金属的磁特性，并在宏观体积内测量大细胞群的磁特性，从而提供有关金属的细胞生物学的宝贵信息。
{"title":"In Situ Magnetometry of Iron in Human Dopaminergic Neurons Using Superresolution MRI and Ion-Beam Microscopy","authors":"Malte Brammerloh, Renat Sibgatulin, Karl-Heinz Herrmann, Markus Morawski, Tilo Reinert, Carsten Jäger, Roland Müller, Gerald Falkenberg, Dennis Brückner, Kerrin J. Pine, Andreas Deistung, Valerij G. Kiselev, Jürgen R. Reichenbach, Nikolaus Weiskopf, Evgeniya Kirilina","doi":"10.1103/physrevx.14.021041","DOIUrl":"https://doi.org/10.1103/physrevx.14.021041","url":null,"abstract":"Paramagnetic transition metals play a crucial role as cofactors in various cellular catalytic processes. However, their high concentrations in reactive oxidation states can induce oxidative stress, resulting in cell dysfunction or death. Hence, it is vital to have methods to monitor metal concentrations and paramagnetic properties in cells for medicine and cell biology. Here we present a novel multimodal method for in-cell magnetometry enabling direct measurement of metal magnetic properties within individual cells in tissue, without prior isolation and at room temperature. Individual cell magnetic moments are measured using superresolution magnetic resonance imaging (MRI) microscopy at 9.4 T by detecting microscopic magnetic-field perturbations around the cells. The cellular metal content is quantified using ion-beam microscopy or synchrotron micro-x-ray fluorescence for the same cells. The metal magnetic susceptibility at 9.4 T is then obtained from the slope of the cell magnetic moments’ dependence on cell metal content. To estimate the susceptibility at lower fields, multifield MR relaxometry and biophysical modeling are employed, extrapolating the 9.4-T susceptibility values to fields as low as 3 T. We apply the new method to determine the susceptibility of iron accumulated in human dopaminergic neurons inside neuromelanin, the by-product of dopamine synthesis. The susceptibility of iron in neuromelanin is measured to be <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mrow><mi>χ</mi></mrow><mrow><mi>ρ</mi></mrow></msub><mo>=</mo><mo stretchy=\"false\">(</mo><mn>2.98</mn><mo>±</mo><mn>0.19</mn><mo stretchy=\"false\">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>6</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mi mathvariant=\"normal\">m</mi><mn>3</mn></msup><mo>/</mo><mi>kg</mi></mrow></math> providing unique insights into the biochemistry of iron inside dopaminergic neurons. The obtained value reveals a predominant monoatomic low-affinity iron-binding site within neuromelanin, indicating a higher neurotoxicity of iron than previously suggested. Furthermore, the measured susceptibility value establishes a quantitative relationship between cellular iron concentration and iron-sensitive MRI parameters, which can be noninvasively measured <i>in vivo</i>. This breakthrough paves the way for the <i>in vivo</i> detection of dopaminergic neuron density and iron load, requiring a standard clinical MRI scanner only. It promises to facilitate early diagnosis of Parkinson’s disease. In conclusion, our presented novel method enables the direct measurements of magnetic properties of paramagnetic metals within single cells with high sensitivity and across large cell groups within a macroscopic volume, providing invaluable information about the cellular biology of metals.","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":null,"pages":null},"PeriodicalIF":12.5,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141304359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：