Pub Date : 2024-09-03DOI: 10.1103/physrevb.110.094304
Julien Despres, Leonardo Mazza, Marco Schirò
We present the spin-wave theory of the excitation spectrum and quench dynamics of the non-Hermitian transverse-field Ising model. The complex excitation spectrum is obtained for a generic hypercubic lattice using the linear approximation of the Holstein-Primakoff transformation together with the complex bosonic Bogolyubov transformation. In the one-dimensional case, our result compares very well with the exact quasiparticle dispersion relation obtained via a fermionic representation of the problem, at least in the regime of large dissipation and transverse field. When applied to the quench dynamics, however, we show that the linear spin-wave approximation breaks down and the bosonic theory is plagued by a divergence at finite times. We understand the origin of this instability using a single-mode approximation. While limited to short times, we show that this approach allows us to characterize the dynamics arising from the quench of the dissipative term and the light-cone structure of the propagation quantum correlations. Furthermore, for the one-dimensional case, the linear spin-wave dynamics shows good agreement with the exact fermionic solution, both for the local magnetization and the spin-spin correlations.
{"title":"Breakdown of linear spin-wave theory in a non-Hermitian quantum spin chain","authors":"Julien Despres, Leonardo Mazza, Marco Schirò","doi":"10.1103/physrevb.110.094304","DOIUrl":"https://doi.org/10.1103/physrevb.110.094304","url":null,"abstract":"We present the spin-wave theory of the excitation spectrum and quench dynamics of the non-Hermitian transverse-field Ising model. The complex excitation spectrum is obtained for a generic hypercubic lattice using the linear approximation of the Holstein-Primakoff transformation together with the complex bosonic Bogolyubov transformation. In the one-dimensional case, our result compares very well with the exact quasiparticle dispersion relation obtained via a fermionic representation of the problem, at least in the regime of large dissipation and transverse field. When applied to the quench dynamics, however, we show that the linear spin-wave approximation breaks down and the bosonic theory is plagued by a divergence at finite times. We understand the origin of this instability using a single-mode approximation. While limited to short times, we show that this approach allows us to characterize the dynamics arising from the quench of the dissipative term and the light-cone structure of the propagation quantum correlations. Furthermore, for the one-dimensional case, the linear spin-wave dynamics shows good agreement with the exact fermionic solution, both for the local magnetization and the spin-spin correlations.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-03DOI: 10.1103/physrevb.110.104406
Caleb Webb, Shufeng Zhang
The magnon current holds substantial importance in facilitating the transfer of angular momentum in spin-based electronics. However, the magnon current in three-dimensional magnetic materials remains orders of magnitude too small for applications. In contrast, magnon numbers in two-dimensional systems exhibit significant enhancement and are markedly influenced by external magnetic fields. Here, we investigate the magnon current in a two- dimensional easy-axis ferromagnet and find a large magnon magnetoresistance (LMMR) effect, wherein the change of the magnon conductance can reach as high as a thousand percent in a moderate magnetic field. Moreover, the magnitude of the LMMR exhibits significant dependence on the orientation of the magnetic field due to the interplay between magnon-conserving and non-magnon-conserving scattering. We propose a nonlocal magnon-mediated electrical drag experiment for the possible experimental observation of the predicted effect. With the LMMR effect and a much larger magnon number, magnon current in 2D materials shows promise as a primary source for spin transport in spintronics devices.
{"title":"Large magnon magnetoresistance of two-dimensional ferromagnets","authors":"Caleb Webb, Shufeng Zhang","doi":"10.1103/physrevb.110.104406","DOIUrl":"https://doi.org/10.1103/physrevb.110.104406","url":null,"abstract":"The magnon current holds substantial importance in facilitating the transfer of angular momentum in spin-based electronics. However, the magnon current in three-dimensional magnetic materials remains orders of magnitude too small for applications. In contrast, magnon numbers in two-dimensional systems exhibit significant enhancement and are markedly influenced by external magnetic fields. Here, we investigate the magnon current in a two- dimensional easy-axis ferromagnet and find a large magnon magnetoresistance (LMMR) effect, wherein the change of the magnon conductance can reach as high as a thousand percent in a moderate magnetic field. Moreover, the magnitude of the LMMR exhibits significant dependence on the orientation of the magnetic field due to the interplay between magnon-conserving and non-magnon-conserving scattering. We propose a nonlocal magnon-mediated electrical drag experiment for the possible experimental observation of the predicted effect. With the LMMR effect and a much larger magnon number, magnon current in 2D materials shows promise as a primary source for spin transport in spintronics devices.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-03DOI: 10.1103/physrevb.110.104407
Zezhong Li, Mengwei Liu, Dongwei Wang, Enke Liu, Zhuhong Liu
The <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">F</mi><msub><mi mathvariant="normal">e</mi><mn>3</mn></msub><mi>Ga</mi></mrow></math> alloy with <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>D</mi><msub><mn>0</mn><mn>3</mn></msub></mrow></math> phase has been reported to exhibit remarkable anomalous transport properties arising from the topological nontrivial nodal lines. In this study, the effect of Mn doping on the magnetic, electronic, and anomalous transport properties of polycrystalline <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">F</mi><msub><mi mathvariant="normal">e</mi><mrow><mn>3</mn><mo>−</mo><mi>x</mi></mrow></msub><mi mathvariant="normal">M</mi><msub><mi mathvariant="normal">n</mi><mi>x</mi></msub><mi>Ga</mi></mrow></math> (<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>x</mi><mo>=</mo><mn>0</mn></mrow></math>, 0.4, 0.6, and 1) are investigated. As the Mn doping level increases, the saturated magnetization at 10 K gradually decreases, while the anomalous Hall resistivity <math xmlns="http://www.w3.org/1998/Math/MathML"><msubsup><mi>ρ</mi><mrow><mi>x</mi><mi>y</mi></mrow><mi>A</mi></msubsup></math> shows a significant increasing trend, reaching a maximum value of 7.2 µΩ cm in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">F</mi><msub><mi mathvariant="normal">e</mi><mn>2</mn></msub><mi>MnGa</mi></mrow></math>. The analysis of anomalous Hall effect (AHE) based on the expanded scaling mechanism proposed by Tian <i>et al.</i> [<span>Phys. Rev. Lett.</span> <b>103</b>, 087206 (2009)] suggests that the AHE in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">F</mi><msub><mi mathvariant="normal">e</mi><mn>3</mn></msub><mi>Ga</mi></mrow></math> is dominated by intrinsic mechanism, with an intrinsic anomalous Hall conductivity (<math xmlns="http://www.w3.org/1998/Math/MathML"><msubsup><mi>σ</mi><mrow><mi>x</mi><mi>y</mi></mrow><mi>int</mi></msubsup></math>) of 288 S/cm. In samples with <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>x</mi><mo>=</mo><mn>0.4</mn></mrow></math>, extrinsic impurity and phonon scattering cannot be neglected and <math xmlns="http://www.w3.org/1998/Math/MathML"><msubsup><mi>σ</mi><mrow><mi>x</mi><mi>y</mi></mrow><mi>int</mi></msubsup></math> decreases to 174 S/cm. As <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi></math> increases to 0.6, the intrinsic mechanism vanishes and the extrinsic impurity and phonon-scattering mechanisms become dominant in the AHE. A further enhanced extrinsic scattering in the AHE is observed in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">F</mi><msub><mi mathvariant="normal">e</mi><mn>2</mn></msub><mi>MnGa</mi></mrow></math> at low temperature with an anomalous Hall conductivity of 237 S/cm at 10 K. From <i>ab initio</i> calculations, we notice a <math xmlns="http://www.w3.org
据报道，具有 D03 相的 Fe3Ga 合金因拓扑非奇异结线而表现出显著的反常输运特性。本研究探讨了掺杂锰对多晶 Fe3-xMnxGa（x=0、0.4、0.6 和 1）的磁性、电子和反常输运特性的影响。随着锰掺杂水平的提高，10 K 时的饱和磁化率逐渐降低，而反常霍尔电阻率 ρxyA 则呈显著上升趋势，在 Fe2MnGa 中达到最大值 7.2 µΩ cm。根据 Tian 等人[Phys. Rev. Lett. 103, 087206 (2009)]提出的扩展缩放机制对反常霍尔效应（AHE）的分析表明，Fe3Ga 中的反常霍尔效应是由本征机制主导的，本征反常霍尔电导率（σxyint）为 288 S/cm。在 x=0.4 的样品中，外在杂质和声子散射无法忽略，σxyint 下降到 174 S/cm。当 x 增大到 0.6 时，内在机制消失，外在杂质和声子散射机制成为 AHE 的主导。根据 ab initio 计算，我们注意到在 Fe3Ga 合金中，费米级（EF）下约 -0.5 eV 处有一个 2310 S/cm 的 σxyint 峰，它源自六个相连的节点环。当一个铁原子被锰取代时，在 Fe2MnGa 中，该峰值移至费米水平（EF）以上 0.5 eV 处。我们认为，在 Fe3Ga 中用 Mn 部分掺杂 Fe 可能会使 EF 附近的 σxyint 大峰值发生变化。
{"title":"Tuning the anomalous Hall effect of the high Curie temperature nodal-line metal Fe3Ga via Mn doping and associated band topology","authors":"Zezhong Li, Mengwei Liu, Dongwei Wang, Enke Liu, Zhuhong Liu","doi":"10.1103/physrevb.110.104407","DOIUrl":"https://doi.org/10.1103/physrevb.110.104407","url":null,"abstract":"The <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">F</mi><msub><mi mathvariant=\"normal\">e</mi><mn>3</mn></msub><mi>Ga</mi></mrow></math> alloy with <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>D</mi><msub><mn>0</mn><mn>3</mn></msub></mrow></math> phase has been reported to exhibit remarkable anomalous transport properties arising from the topological nontrivial nodal lines. In this study, the effect of Mn doping on the magnetic, electronic, and anomalous transport properties of polycrystalline <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">F</mi><msub><mi mathvariant=\"normal\">e</mi><mrow><mn>3</mn><mo>−</mo><mi>x</mi></mrow></msub><mi mathvariant=\"normal\">M</mi><msub><mi mathvariant=\"normal\">n</mi><mi>x</mi></msub><mi>Ga</mi></mrow></math> (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>x</mi><mo>=</mo><mn>0</mn></mrow></math>, 0.4, 0.6, and 1) are investigated. As the Mn doping level increases, the saturated magnetization at 10 K gradually decreases, while the anomalous Hall resistivity <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msubsup><mi>ρ</mi><mrow><mi>x</mi><mi>y</mi></mrow><mi>A</mi></msubsup></math> shows a significant increasing trend, reaching a maximum value of 7.2 µΩ cm in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">F</mi><msub><mi mathvariant=\"normal\">e</mi><mn>2</mn></msub><mi>MnGa</mi></mrow></math>. The analysis of anomalous Hall effect (AHE) based on the expanded scaling mechanism proposed by Tian <i>et al.</i> [<span>Phys. Rev. Lett.</span> <b>103</b>, 087206 (2009)] suggests that the AHE in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">F</mi><msub><mi mathvariant=\"normal\">e</mi><mn>3</mn></msub><mi>Ga</mi></mrow></math> is dominated by intrinsic mechanism, with an intrinsic anomalous Hall conductivity (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msubsup><mi>σ</mi><mrow><mi>x</mi><mi>y</mi></mrow><mi>int</mi></msubsup></math>) of 288 S/cm. In samples with <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>x</mi><mo>=</mo><mn>0.4</mn></mrow></math>, extrinsic impurity and phonon scattering cannot be neglected and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msubsup><mi>σ</mi><mrow><mi>x</mi><mi>y</mi></mrow><mi>int</mi></msubsup></math> decreases to 174 S/cm. As <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>x</mi></math> increases to 0.6, the intrinsic mechanism vanishes and the extrinsic impurity and phonon-scattering mechanisms become dominant in the AHE. A further enhanced extrinsic scattering in the AHE is observed in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">F</mi><msub><mi mathvariant=\"normal\">e</mi><mn>2</mn></msub><mi>MnGa</mi></mrow></math> at low temperature with an anomalous Hall conductivity of 237 S/cm at 10 K. From <i>ab initio</i> calculations, we notice a <math xmlns=\"http://www.w3.org","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-03DOI: 10.1103/physrevb.110.l121101
Ceren B. Dag, Vasil Rokaj
Strongly coupling materials to cavity fields can affect their electronic properties altering the phases of matter. We study monolayer graphene whose electrons are coupled to both left and right circularly polarized vacuum fluctuations, and time-reversal symmetry is broken due to a phase shift between the two polarizations. We develop a many-body perturbative theory, and derive cavity-mediated electronic interactions. This theory leads to a gap equation which predicts a topological band gap at Dirac nodes in vacuum and when the cavity is prepared in an excited Fock state. Remarkably, topological band gaps also open in light-matter hybridization points away from the Dirac nodes giving rise to photoelectron bands with high Chern numbers. We reveal that the physical mechanism behind this phenomenon is generic and due to the exchange of photons with electronic matter at the hybridization points. Specifically, the number and polarization of exchanged photons directly determine the band topology of graphene subject to enhanced chiral vacuum fluctuations. Hence, our theory shows that graphene-based materials could host Chern insulator phases in engineered electromagnetic environments, bridging cavity quantum electrodynamics to Floquet engineering of materials while protected from the ensuing heating effects.
{"title":"Engineering topology in graphene with chiral cavities","authors":"Ceren B. Dag, Vasil Rokaj","doi":"10.1103/physrevb.110.l121101","DOIUrl":"https://doi.org/10.1103/physrevb.110.l121101","url":null,"abstract":"Strongly coupling materials to cavity fields can affect their electronic properties altering the phases of matter. We study monolayer graphene whose electrons are coupled to both left and right circularly polarized vacuum fluctuations, and time-reversal symmetry is broken due to a phase shift between the two polarizations. We develop a many-body perturbative theory, and derive cavity-mediated electronic interactions. This theory leads to a gap equation which predicts a topological band gap at Dirac nodes in vacuum and when the cavity is prepared in an excited Fock state. Remarkably, topological band gaps also open in light-matter hybridization points away from the Dirac nodes giving rise to photoelectron bands with high Chern numbers. We reveal that the physical mechanism behind this phenomenon is generic and due to the exchange of photons with electronic matter at the hybridization points. Specifically, the number and polarization of exchanged photons directly determine the band topology of graphene subject to enhanced chiral vacuum fluctuations. Hence, our theory shows that graphene-based materials could host Chern insulator phases in engineered electromagnetic environments, bridging cavity quantum electrodynamics to Floquet engineering of materials while protected from the ensuing heating effects.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-03DOI: 10.1103/physrevb.110.094101
J. Philippe, F. Elson, N. P. M. Casati, S. Sanz, M. Metzelaars, O. Shliakhtun, O. K. Forslund, J. Lass, T. Shiroka, A. Linden, D. G. Mazzone, J. Ollivier, S. Shin, M. Medarde, B. Lake, M. Månsson, M. Bartkowiak, B. Normand, P. Kögerler, Y. Sassa, M. Janoschek, G. Simutis
Low-dimensional quantum magnets are a versatile materials platform for studying the emergent many-body physics and collective excitations that can arise even in systems with only short-range interactions. Understanding their low-temperature structure and spin Hamiltonian is key to explaining their magnetic properties, including unconventional quantum phases, phase transitions, and excited states. We study the metal-organic coordination compound and its deuterated counterpart, which upon its discovery was identified as a candidate two-leg quantum spin ladder in the strong-leg coupling regime. By growing large single crystals and probing them with both bulk and microscopic techniques, we deduce that two previously unknown structural phase transitions take place between 136 and 113 K. The low-temperature structure has a monoclinic unit cell that gives rise to two inequivalent spin ladders. We further confirm the absence of long-range magnetic order down to 30 mK and investigate the implications of this two-ladder structure for the magnetic properties of by analyzing our own specific-heat and susceptibility data.
{"title":"(C5H9NH3)2CuBr4: A metal-organic two-ladder quantum magnet","authors":"J. Philippe, F. Elson, N. P. M. Casati, S. Sanz, M. Metzelaars, O. Shliakhtun, O. K. Forslund, J. Lass, T. Shiroka, A. Linden, D. G. Mazzone, J. Ollivier, S. Shin, M. Medarde, B. Lake, M. Månsson, M. Bartkowiak, B. Normand, P. Kögerler, Y. Sassa, M. Janoschek, G. Simutis","doi":"10.1103/physrevb.110.094101","DOIUrl":"https://doi.org/10.1103/physrevb.110.094101","url":null,"abstract":"Low-dimensional quantum magnets are a versatile materials platform for studying the emergent many-body physics and collective excitations that can arise even in systems with only short-range interactions. Understanding their low-temperature structure and spin Hamiltonian is key to explaining their magnetic properties, including unconventional quantum phases, phase transitions, and excited states. We study the metal-organic coordination compound <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mrow><mo>(</mo><msub><mi mathvariant=\"normal\">C</mi><mn>5</mn></msub><msub><mi mathvariant=\"normal\">H</mi><mn>9</mn></msub><msub><mi>NH</mi><mn>3</mn></msub><mo>)</mo></mrow><mn>2</mn></msub><msub><mi>CuBr</mi><mn>4</mn></msub></mrow></math> and its deuterated counterpart, which upon its discovery was identified as a candidate two-leg quantum <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>(</mo><mi>S</mi><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mo>)</mo></mrow></math> spin ladder in the strong-leg coupling regime. By growing large single crystals and probing them with both bulk and microscopic techniques, we deduce that two previously unknown structural phase transitions take place between 136 and 113 K. The low-temperature structure has a monoclinic unit cell that gives rise to two inequivalent spin ladders. We further confirm the absence of long-range magnetic order down to 30 mK and investigate the implications of this two-ladder structure for the magnetic properties of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mrow><mo>(</mo><msub><mi mathvariant=\"normal\">C</mi><mn>5</mn></msub><msub><mi mathvariant=\"normal\">H</mi><mn>9</mn></msub><msub><mi>NH</mi><mn>3</mn></msub><mo>)</mo></mrow><mn>2</mn></msub><msub><mi>CuBr</mi><mn>4</mn></msub></mrow></math> by analyzing our own specific-heat and susceptibility data.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-03DOI: 10.1103/physrevb.110.104502
Jozef Haniš, Marko Milivojević, Martin Gmitra
The monolayer with Rashba spin-orbit coupling represents a paradigmatic example of an Ising superconductor on a substrate. Using a single-band model and symmetry analysis, we present general superconducting pairing functions beyond the nearest-neighbor approximation, uncovering new types of gap functions, including the nodal singlet gap function and the triplet nonunitary pairing function that breaks time-reversal symmetry. The nonunitarity builts in the asymmetrical band dispersion in the superconducting quasiparticle energy spectra. Performing exact -matrix calculations of quasiparticle interference due to a single scalar impurity scattering, we found that the interference patterns possess characteristic features distinguishing the type of pairing and possible nematic and chiral symmetry violations.
具有拉什巴自旋轨道耦合的 NbSe2 单层是衬底上伊辛超导体的典型例子。利用单带模型和对称性分析，我们提出了超越近邻近似的一般超导配对函数，揭示了新型间隙函数，包括节点单线隙函数和打破时间逆对称性的三重非单元配对函数。非统一性在超导准粒子能谱中构建了非对称带色散。在对单标量杂质散射引起的类粒子干涉进行精确的 T 矩阵计算时，我们发现干涉模式具有区分配对类型以及可能的向列对称性和手性对称性违反的特征。
{"title":"Distinguishing nodal and nonunitary superconductivity in quasiparticle interference of an Ising superconductor with Rashba spin-orbit coupling: The example of NbSe2","authors":"Jozef Haniš, Marko Milivojević, Martin Gmitra","doi":"10.1103/physrevb.110.104502","DOIUrl":"https://doi.org/10.1103/physrevb.110.104502","url":null,"abstract":"The <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>NbSe</mi><mn>2</mn></msub></math> monolayer with Rashba spin-orbit coupling represents a paradigmatic example of an Ising superconductor on a substrate. Using a single-band model and symmetry analysis, we present general superconducting pairing functions beyond the nearest-neighbor approximation, uncovering new types of gap functions, including the nodal singlet gap function and the triplet nonunitary pairing function that breaks time-reversal symmetry. The nonunitarity builts in the asymmetrical band dispersion in the superconducting quasiparticle energy spectra. Performing exact <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>T</mi></math>-matrix calculations of quasiparticle interference due to a single scalar impurity scattering, we found that the interference patterns possess characteristic features distinguishing the type of pairing and possible nematic and chiral symmetry violations.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-03DOI: 10.1103/physrevb.110.115403
Arnob Kumar Ghosh, Arijit Saha, Tanay Nag
We consider a non-Hermitian (NH) analog of a second-order topological insulator, protected by chiral symmetry, in the presence of next-nearest-neighbor hopping elements to theoretically investigate the interplay beyond the first-nearest-neighbor hopping amplitudes and topological order away from Hermiticity. In addition to the four zero-energy corner modes present in the first-nearest-neighbor hopping model, we uncover that the second-nearest-neighbor hopping introduces another topological phase with 16 zero-energy corner modes. Importantly, the NH effects are manifested in altering the Hermitian phase boundaries for both of the models. While comparing the complex energy spectrum under open boundary conditions, and bi-orthogonalized quadrupolar winding number in real space, we resolve the apparent anomaly in the bulk boundary correspondence of the NH system as compared to the Hermitian counterpart by incorporating the effect of the non-Bloch form of momentum into the mass term. The above invariant is also capable of capturing the phase boundaries between the two different topological phases where the degeneracy of the corner modes is evident, as exclusively observed for the second-nearest-neighbor model.
{"title":"Corner modes in non-Hermitian next-nearest-neighbor hopping model","authors":"Arnob Kumar Ghosh, Arijit Saha, Tanay Nag","doi":"10.1103/physrevb.110.115403","DOIUrl":"https://doi.org/10.1103/physrevb.110.115403","url":null,"abstract":"We consider a non-Hermitian (NH) analog of a second-order topological insulator, protected by chiral symmetry, in the presence of next-nearest-neighbor hopping elements to theoretically investigate the interplay beyond the first-nearest-neighbor hopping amplitudes and topological order away from Hermiticity. In addition to the four zero-energy corner modes present in the first-nearest-neighbor hopping model, we uncover that the second-nearest-neighbor hopping introduces another topological phase with 16 zero-energy corner modes. Importantly, the NH effects are manifested in altering the Hermitian phase boundaries for both of the models. While comparing the complex energy spectrum under open boundary conditions, and bi-orthogonalized quadrupolar winding number in real space, we resolve the apparent anomaly in the bulk boundary correspondence of the NH system as compared to the Hermitian counterpart by incorporating the effect of the non-Bloch form of momentum into the mass term. The above invariant is also capable of capturing the phase boundaries between the two different topological phases where the degeneracy of the corner modes is evident, as exclusively observed for the second-nearest-neighbor model.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-03DOI: 10.1103/physrevb.110.115407
Francesco Macheda, Francesco Mauri, Thibault Sohier
Plasmons and polar phonons are elementary electrodynamic excitations of matter. In two dimensions and at long wavelengths, they couple to light and act as the system polaritons. They also dictate the scattering of charged carriers. Van der Waals heterostructures offer the opportunity to couple excitations from different layers via long-range Coulomb interactions, modifying both their dispersion and their scattering of electrons. Even when the excitations do not couple, they are still influenced by the screening from all layers, leading to complex dynamical interactions between electrons, plasmons, and polar phonons. We develop an efficient ab initio model to solve the dynamical electric response of Van der Waals heterostructures, accompanied by a formalism to extract relevant spectroscopic and transport quantities. Notably, we obtain scattering rates for electrons of the heterostructure coupling remotely with electrodynamic excitations. We apply those developments to BN-capped graphene, in which polar phonons from BN couple to plasmons in graphene. We study the nature of the coupled excitations, their dispersion and their coupling to graphene's electrons. Regimes driven by either phonons or plasmons are identified, as well as a truly hybrid regime corresponding to the plasmon-phonon-polariton at long wavelengths. Those are studied as a function of the graphene's Fermi level and the number of BN layers. In contrast with standard descriptions in terms of surface-optical phonons, we find that the electron-phonon interaction stems from several different modes. Moreover, the dynamical screening of the coupling between BN's LO phonons and graphene's electrons crosses over from inefficient to metal-like depending on the relative value of the phonons' frequency and the energetic onset of interband transitions. While the coupling is significant in general, the associated scattering of graphene's carriers is found to be negligible with respect to the particularly large one coming from intrinsic phonons in the context of electronic transport.
质子和极性声子是物质的基本电动激元。在二维和长波长条件下，它们与光耦合，成为系统的极化子。它们还决定了带电载流子的散射。范德华异质结构提供了通过长程库仑相互作用耦合来自不同层的激发的机会，从而改变了它们的色散和电子散射。即使激发没有耦合，它们仍然会受到来自各层的屏蔽的影响，从而导致电子、质子和极性声子之间复杂的动态相互作用。我们建立了一个高效的非初始模型来求解范德瓦尔斯异质结构的动态电响应，并通过一个形式主义来提取相关的光谱和传输量。值得注意的是，我们获得了异质结构电子与电动激元远程耦合的散射率。我们将这些研究成果应用于 BN 封装的石墨烯，其中来自 BN 的极性声子与石墨烯中的质子耦合。我们研究了耦合激子的性质、其分散性及其与石墨烯电子的耦合。我们确定了声子或质子驱动的机制，以及与长波长质子-声子-极化子相对应的真正混合机制。这些都是作为石墨烯费米级和 BN 层数的函数进行研究的。与标准的表面光声子描述不同，我们发现电子与声子的相互作用源于几种不同的模式。此外，BN 的 LO 声子与石墨烯电子之间耦合的动态筛选从低效到类似金属，取决于声子频率的相对值和带间转换的能量起始。虽然这种耦合在一般情况下是显著的，但在电子传输的背景下，石墨烯载流子的相关散射与来自本征声子的特别大的散射相比可以忽略不计。
{"title":"Ab initio Van der Waals electrodynamics: Polaritons and electron scattering from plasmons and phonons in BN-capped graphene","authors":"Francesco Macheda, Francesco Mauri, Thibault Sohier","doi":"10.1103/physrevb.110.115407","DOIUrl":"https://doi.org/10.1103/physrevb.110.115407","url":null,"abstract":"Plasmons and polar phonons are elementary electrodynamic excitations of matter. In two dimensions and at long wavelengths, they couple to light and act as the system polaritons. They also dictate the scattering of charged carriers. Van der Waals heterostructures offer the opportunity to couple excitations from different layers via long-range Coulomb interactions, modifying both their dispersion and their scattering of electrons. Even when the excitations do not couple, they are still influenced by the screening from all layers, leading to complex dynamical interactions between electrons, plasmons, and polar phonons. We develop an efficient <i>ab initio</i> model to solve the dynamical electric response of Van der Waals heterostructures, accompanied by a formalism to extract relevant spectroscopic and transport quantities. Notably, we obtain scattering rates for electrons of the heterostructure coupling remotely with electrodynamic excitations. We apply those developments to BN-capped graphene, in which polar phonons from BN couple to plasmons in graphene. We study the nature of the coupled excitations, their dispersion and their coupling to graphene's electrons. Regimes driven by either phonons or plasmons are identified, as well as a truly hybrid regime corresponding to the plasmon-phonon-polariton at long wavelengths. Those are studied as a function of the graphene's Fermi level and the number of BN layers. In contrast with standard descriptions in terms of surface-optical phonons, we find that the electron-phonon interaction stems from several different modes. Moreover, the dynamical screening of the coupling between BN's LO phonons and graphene's electrons crosses over from inefficient to metal-like depending on the relative value of the phonons' frequency and the energetic onset of interband transitions. While the coupling is significant in general, the associated scattering of graphene's carriers is found to be negligible with respect to the particularly large one coming from intrinsic phonons in the context of electronic transport.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-03DOI: 10.1103/physrevb.110.125401
M. Maneesh Kumar, Sanjay Sarkar, Amit Agarwal
Electric field-induced modulation of the optical properties is crucial for amplitude and phase modulators used in photonic devices. Here, we present a comprehensive study of the band geometry induced electro-optic effect, specifically focusing on the Fermi surface and disorder-induced contributions. These contributions are crucial for metallic and semimetallic systems and for optical frequencies comparable to or smaller than the scattering rates. We highlight the importance of the quantum metric and metric connection in generating the phenomenon in parity-time reversal () symmetric systems such as CuMnAs. Our findings establish the electro-optic effect as a tool to probe band geometric effects and open different avenues to design electrically controlled efficient amplitude and phase modulators for photonic applications.
{"title":"Band geometry induced electro-optic effect and polarization rotation","authors":"M. Maneesh Kumar, Sanjay Sarkar, Amit Agarwal","doi":"10.1103/physrevb.110.125401","DOIUrl":"https://doi.org/10.1103/physrevb.110.125401","url":null,"abstract":"Electric field-induced modulation of the optical properties is crucial for amplitude and phase modulators used in photonic devices. Here, we present a comprehensive study of the band geometry induced electro-optic effect, specifically focusing on the Fermi surface and disorder-induced contributions. These contributions are crucial for metallic and semimetallic systems and for optical frequencies comparable to or smaller than the scattering rates. We highlight the importance of the quantum metric and metric connection in generating the phenomenon in parity-time reversal (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi mathvariant=\"script\">PT</mi></math>) symmetric systems such as CuMnAs. Our findings establish the electro-optic effect as a tool to probe band geometric effects and open different avenues to design electrically controlled efficient amplitude and phase modulators for photonic applications.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-03DOI: 10.1103/physrevb.110.094403
Kaito Nakamura, Andrey O. Leonov
We reexamine the internal structure of skyrmioniums stabilized in quasi-two-dimensional chiral magnets with easy-axis uniaxial anisotropy. Skyrmioniums are particlelike states of two nested skyrmions with opposite polarities contributing to zero topological charge. The physical principles of skyrmionium stability are drawn from both the analytical analysis with a trial function and from numerical simulations within the framework of micromagnetism. We deduce that the radii of the internal skyrmion with the positive polarity and the ring-shaped external skyrmion with the negative polarity are mutually dependent, which constitutes the paradigm of communicating skyrmions. For large central skyrmions, the skyrmionium transforms into a narrow circular domain wall, whereas for small internal radii, the ring expands, which occurs at the verge of collapsing into an ordinary isolated skyrmion. We show that skyrmioniums may form lattices of two varieties depending on the polarity of the internal skyrmion. At the phase diagram (magnetic field)-(uniaxial anisotropy), both skyrmionium lattices share the same area with one-dimensional spiral states and remain metastable solutions for the whole range of control parameters. By expanding at the critical line, skyrmionium lattices do not release isolated skyrmioniums. Isolated skyrmioniums of just one type exist apart from the corresponding lattice in a narrow field region restricted by the critical line of expansion from below and by the line of collapse above.
{"title":"Mechanism of skyrmionium stability in quasi-two-dimensional chiral magnets","authors":"Kaito Nakamura, Andrey O. Leonov","doi":"10.1103/physrevb.110.094403","DOIUrl":"https://doi.org/10.1103/physrevb.110.094403","url":null,"abstract":"We reexamine the internal structure of skyrmioniums stabilized in quasi-two-dimensional chiral magnets with easy-axis uniaxial anisotropy. Skyrmioniums are particlelike states of two nested skyrmions with opposite polarities contributing to zero topological charge. The physical principles of skyrmionium stability are drawn from both the analytical analysis with a trial function and from numerical simulations within the framework of micromagnetism. We deduce that the radii of the internal skyrmion with the positive polarity and the ring-shaped external skyrmion with the negative polarity are mutually dependent, which constitutes the paradigm of communicating skyrmions. For large central skyrmions, the skyrmionium transforms into a narrow circular domain wall, whereas for small internal radii, the ring expands, which occurs at the verge of collapsing into an ordinary isolated skyrmion. We show that skyrmioniums may form lattices of two varieties depending on the polarity of the internal skyrmion. At the phase diagram (magnetic field)-(uniaxial anisotropy), both skyrmionium lattices share the same area with one-dimensional spiral states and remain metastable solutions for the whole range of control parameters. By expanding at the critical line, skyrmionium lattices do not release isolated skyrmioniums. Isolated skyrmioniums of just one type exist apart from the corresponding lattice in a narrow field region restricted by the critical line of expansion from below and by the line of collapse above.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
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