Chromium-based perovskites have drawn plenty of attention due to their intriguing magnetic properties and potential technique applications. While a complete understanding of the microscopic magnetic mechanisms underlying their macroscopic properties presents great challenges, especially when involving () hybridization and rare earth (RE) orbitals. Here, with the recently discovered molecular analogue of perovskite , abbreviated as , we combine first-principles calculations and a superexchange model to successfully identify an anomalous ferromagnetism (FM)-dominated superexchange interaction between Cr ions originated from the hybridization, which does not follow Goodenough-Kanamori rules. The great sensitivity of the hybridization with respect to the angle of Cr-O-Cr can lead to a significant change in the magnetic interaction of with the angle of Cr-O-Cr varying within only a few degrees, e.g., a ground-state transition from FM to antiferromagnetism. Additionally, the Ce orbitals near the Fermi level can largely reduce this sensitivity by interacting with the Cr orbitals via the virtual charge transfer process. Our results are strongly supported by an extended superexchange model developed with the inclusion of orbitals within the hybridization framework. These findings complete the theory of superexchange magnetism in chromium-based perovskites including RE
{"title":"Direct observation of strong t2g−eg orbital hybridization and effects of f orbitals in a molecular analogue of chromium perovskite","authors":"Mian Wang, Chengzhi Li, Xiang-Guo Li, Yanglong Hou","doi":"10.1103/physrevb.110.l020409","DOIUrl":"https://doi.org/10.1103/physrevb.110.l020409","url":null,"abstract":"Chromium-based perovskites have drawn plenty of attention due to their intriguing magnetic properties and potential technique applications. While a complete understanding of the microscopic magnetic mechanisms underlying their macroscopic properties presents great challenges, especially when involving <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>t</mi><mrow><mn>2</mn><mi>g</mi></mrow></msub><mtext>−</mtext><msub><mi>e</mi><mi>g</mi></msub></mrow></math> (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>t</mi><mtext>−</mtext><mi>e</mi></math>) hybridization and rare earth (RE) <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>f</mi></math> orbitals. Here, with the recently discovered molecular analogue of perovskite <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>[</mo><msubsup><mi>Ce</mi><mn>2</mn><mi>III</mi></msubsup><msup><mi>Ce</mi><mi>IV</mi></msup><msubsup><mi>Cr</mi><mn>8</mn><mi>III</mi></msubsup><msub><mi mathvariant=\"normal\">O</mi><mn>8</mn></msub><msub><mrow><mo>(</mo><msub><mi mathvariant=\"normal\">O</mi><mn>2</mn></msub><mi>CPh</mi><mo>)</mo></mrow><mn>18</mn></msub><mrow><mo>(</mo><msub><mi>HO</mi><mn>2</mn></msub><mi>CPh</mi><mo>)</mo></mrow><mo>]</mo></mrow></math>, abbreviated as <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Ce</mi><mn>3</mn></msub><msub><mi>Cr</mi><mn>8</mn></msub></mrow></math>, we combine first-principles calculations and a superexchange model to successfully identify an anomalous ferromagnetism (FM)-dominated superexchange interaction between Cr ions originated from the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>t</mi><mtext>−</mtext><mi>e</mi></math> hybridization, which does not follow Goodenough-Kanamori rules. The great sensitivity of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>t</mi><mtext>−</mtext><mi>e</mi></math> hybridization with respect to the angle of Cr-O-Cr can lead to a significant change in the magnetic interaction of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Ce</mi><mn>3</mn></msub><msub><mi>Cr</mi><mn>8</mn></msub></mrow></math> with the angle of Cr-O-Cr varying within only a few degrees, e.g., a ground-state transition from FM to antiferromagnetism. Additionally, the Ce <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>f</mi></math> orbitals near the Fermi level can largely reduce this sensitivity by interacting with the Cr <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>d</mi></math> orbitals via the virtual charge transfer process. Our results are strongly supported by an extended superexchange model developed with the inclusion of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>f</mi></math> orbitals within the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>t</mi><mtext>−</mtext><mi>e</mi></math> hybridization framework. These findings complete the theory of superexchange magnetism in chromium-based perovskites including RE <math xmlns=\"http://www.w3.org/1998/Math/Math","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141857810","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 : 2024-07-31DOI: 10.1103/physrevb.110.024115
Ning Ding, Haoshen Ye, Shuai Dong
Sliding ferroelectricity was originally proposed to elucidate the out-of-plane polarization generated by a specific stacking arrangement of nonpolar van der Waals layers. However, the concept of sliding ferroelectricity can be generalized to more geometries. Here, the bulk is theoretically demonstrated as a quasi-one-dimensional sliding ferroelectric material, which exhibits a polarization of perpendicular to the Nb's chains. The most possible ferroelectric switching path is found to be via the interchain sliding along the chain direction, while other paths such as Peierls dimerization of Nb pairs may also work. Moreover, its polarization can be augmented for by hydrostatic pressure up to , beyond which becomes a polar metal. In addition, negative longitudinal piezoelectricity is also predicted.
{"title":"Quasi-one-dimensional sliding ferroelectricity in NbI4","authors":"Ning Ding, Haoshen Ye, Shuai Dong","doi":"10.1103/physrevb.110.024115","DOIUrl":"https://doi.org/10.1103/physrevb.110.024115","url":null,"abstract":"Sliding ferroelectricity was originally proposed to elucidate the out-of-plane polarization generated by a specific stacking arrangement of nonpolar van der Waals layers. However, the concept of sliding ferroelectricity can be generalized to more geometries. Here, the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>NbI</mi><mn>4</mn></msub></math> bulk is theoretically demonstrated as a quasi-one-dimensional sliding ferroelectric material, which exhibits a polarization of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>0.11</mn><mspace width=\"0.28em\"></mspace><mi>µ</mi><mi mathvariant=\"normal\">C</mi><mo>/</mo><msup><mrow><mi>cm</mi></mrow><mn>2</mn></msup></mrow></math> perpendicular to the Nb's chains. The most possible ferroelectric switching path is found to be via the interchain sliding along the chain direction, while other paths such as Peierls dimerization of Nb pairs may also work. Moreover, its polarization can be augmented for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>82</mn><mo>%</mo></mrow></math> by hydrostatic pressure up to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>10</mn><mspace width=\"0.28em\"></mspace><mi>GPa</mi></mrow></math>, beyond which <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>NbI</mi><mn>4</mn></msub></math> becomes a polar metal. In addition, negative longitudinal piezoelectricity is also predicted.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141857851","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}
Recently, quantum anomalous Hall state has been observed in moiré transition metal dichalcogenide bilayers. Its topological physics can be explained by a band-inverted charge transfer insulator model, in which the topological phase transition occurs in the presence of the band inversion. Starting from an effective three-band low-energy model, we investigate the Landau levels and the magneto-optical conductivity of a band-inverted charge transfer insulator on the honeycomb lattice. We derive the real and imaginary parts of the longitudinal conductivity and Hall conductivity using Kubo formalism. We find that the magneto-optical conductivity indicates a discontinuity at the point of band inversion in the low-frequency regime, which can serve as a probe for band topology. It is shown that the charge transfer gap, chemical potential, and magnetic field have a sensitive effect on the magneto-optical conductivity. The unique band structure also changes the peaks in the imaginary part of the Hall conductivity into two distinct contributions of opposite signs. We also study the relationship of the band-inversion signature and transport properties and highlight its distinct features that can be probed experimentally.
{"title":"Magneto-optical conductivity of a band-inverted charge transfer insulator","authors":"Chang Liu, Sha-Sha Ke, Yong Guo, Xiao-Tao Zu, Sean Li, Hai-Feng Lü","doi":"10.1103/physrevb.110.045445","DOIUrl":"https://doi.org/10.1103/physrevb.110.045445","url":null,"abstract":"Recently, quantum anomalous Hall state has been observed in moiré transition metal dichalcogenide bilayers. Its topological physics can be explained by a band-inverted charge transfer insulator model, in which the topological phase transition occurs in the presence of the band inversion. Starting from an effective three-band low-energy model, we investigate the Landau levels and the magneto-optical conductivity of a band-inverted charge transfer insulator on the honeycomb lattice. We derive the real and imaginary parts of the longitudinal conductivity and Hall conductivity using Kubo formalism. We find that the magneto-optical conductivity indicates a discontinuity at the point of band inversion in the low-frequency regime, which can serve as a probe for band topology. It is shown that the charge transfer gap, chemical potential, and magnetic field have a sensitive effect on the magneto-optical conductivity. The unique band structure also changes the peaks in the imaginary part of the Hall conductivity into two distinct contributions of opposite signs. We also study the relationship of the band-inversion signature and transport properties and highlight its distinct features that can be probed experimentally.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141857808","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 : 2024-07-31DOI: 10.1103/physrevb.110.l020408
Mu-Kun Lee, Rubén M. Otxoa, Masahito Mochizuki
We theoretically discover the possible emergence of reentrant Walker breakdowns for current-driven domain walls in layered antiferromagnets, in striking contrast to the unique Walker breakdown in ferromagnets. We reveal that the Lorentz contraction of domain wall width in antiferromagnets gives rise to nonlinear current dependence of the wall velocity and the predicted multiple Walker breakdowns. The dominant efficiency of the current-induced staggered spin-orbit torque over the spin-transfer torque to drive the domain wall motion is also demonstrated. These findings are expected to be observed in synthetic antiferromagnets experimentally and provide an important contribution to the growing research field of antiferromagnetic spintronics.
{"title":"Predicted multiple Walker breakdowns for current-driven domain wall motion in antiferromagnets","authors":"Mu-Kun Lee, Rubén M. Otxoa, Masahito Mochizuki","doi":"10.1103/physrevb.110.l020408","DOIUrl":"https://doi.org/10.1103/physrevb.110.l020408","url":null,"abstract":"We theoretically discover the possible emergence of reentrant Walker breakdowns for current-driven domain walls in layered antiferromagnets, in striking contrast to the unique Walker breakdown in ferromagnets. We reveal that the Lorentz contraction of domain wall width in antiferromagnets gives rise to nonlinear current dependence of the wall velocity and the predicted multiple Walker breakdowns. The dominant efficiency of the current-induced staggered spin-orbit torque over the spin-transfer torque to drive the domain wall motion is also demonstrated. These findings are expected to be observed in synthetic antiferromagnets experimentally and provide an important contribution to the growing research field of antiferromagnetic spintronics.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141857715","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 : 2024-07-30DOI: 10.1103/physrevb.110.014443
Byungryul Jang, G. M. Pastor
The anisotropic antisymmetric Dzyaloshinskii-Moriya (DM) interactions between local magnetic moments and , which can be induced by an external electric field (EF) are investigated in the framework of density functional theory by considering all , and freestanding transition metal dimers. The possibilities of triggering and reversibly tuning chiral magnetic couplings by electric means are demonstrated. The dependence of the DM-coupling vector on the EF strength is shown to be approximately linear for V/Å, with only minor third-order corrections. The first- and third-order zero-field electric susceptibility of the DM couplings are determined and analyzed as a function of -band filling. The correlations between them and the chirality of the spin-orbit energy are displayed. From a microscopic perspective, the EF-induced DM couplings are shown to stem from the permanent electric dipole moments that are already present in the field-free dimers whenever their local magnetic moments are not collinear. The symmetry rules governing and its chirality are discussed. Finally, the dependence of the EF-induced DM couplings on the degree of noncollinearity of the magnetic order is quantified by varying systematically the angle between the local moments. While the electronic calculations show that the changes in the effective can be quite important for arbitrary , one also observes that depends weakly on
{"title":"Reversible electric field manipulation of the Dzyaloshinskii-Moriya interactions in transition metal dimers","authors":"Byungryul Jang, G. M. Pastor","doi":"10.1103/physrevb.110.014443","DOIUrl":"https://doi.org/10.1103/physrevb.110.014443","url":null,"abstract":"The anisotropic antisymmetric Dzyaloshinskii-Moriya (DM) interactions between local magnetic moments <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi mathvariant=\"bold-italic\">μ</mi></mrow><mi>i</mi></msub></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi mathvariant=\"bold-italic\">μ</mi></mrow><mi>j</mi></msub></math>, which can be induced by an external electric field (EF) are investigated in the framework of density functional theory by considering all <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>3</mn><mi>d</mi></mrow><mo>,</mo><mo> </mo><mrow><mn>4</mn><mi>d</mi></mrow></math>, and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>5</mn><mi>d</mi></mrow></math> freestanding transition metal dimers. The possibilities of triggering and reversibly tuning chiral magnetic couplings by electric means are demonstrated. The dependence of the DM-coupling vector <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"bold-italic\">D</mi><mrow><mi>i</mi><mi>j</mi></mrow></msub></math> on the EF strength <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>E</mi></math> is shown to be approximately linear for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>|</mo><mi>E</mi><mo>|</mo><mo>≤</mo><mn>0.6</mn></mrow></math> V/Å, with only minor third-order corrections. The first- and third-order zero-field electric susceptibility of the DM couplings are determined and analyzed as a function of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>d</mi></math>-band filling. The correlations between them and the chirality of the spin-orbit energy are displayed. From a microscopic perspective, the EF-induced DM couplings are shown to stem from the permanent electric dipole moments <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi mathvariant=\"bold-italic\">p</mi></mrow><mn>0</mn></msup></math> that are already present in the field-free dimers whenever their local magnetic moments are not collinear. The symmetry rules governing <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi mathvariant=\"bold-italic\">p</mi></mrow><mn>0</mn></msup></math> and its chirality are discussed. Finally, the dependence of the EF-induced DM couplings on the degree of noncollinearity of the magnetic order is quantified by varying systematically the angle <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>θ</mi></math> between the local moments. While the electronic calculations show that the changes in the effective <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"bold-italic\">D</mi><mrow><mi>i</mi><mi>j</mi></mrow></msub></math> can be quite important for arbitrary <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>θ</mi></math>, one also observes that <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"bold-italic\">D</mi><mrow><mi>i</mi><mi>j</mi></mrow></msub></math> depends weakly on <math xmlns=\"http://www.w3.org/1998/M","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141794592","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 : 2024-07-30DOI: 10.1103/physrevb.110.024520
Sebastian Miles, David van Driel, Michael Wimmer, Chun-Xiao Liu
We propose to implement a Kitaev chain based on an array of alternating normal and superconductor hybrid quantum dots embedded in semiconductors. In particular, the orbitals in the dot and the Andreev bound states in the hybrid are now on an equal footing, and both emerge as low-energy degrees of freedom in the Kitaev chain, with the couplings being induced by direct tunneling. Due to the electron and hole components in the Andreev bound state, this coupling is simultaneously of the normal and Andreev types, with their ratio being tunable by varying one or several of the experimentally accessible physical parameters, e.g., strength and direction of the Zeeman field, as well as changing the proximity effect on the normal quantum dots. As such, it becomes feasible to realize a two-site Kitaev chain in a simple setup with only one normal quantum dot and one hybrid segment. Interestingly, when scaling up the system to a three-site Kitaev chain, next-nearest-neighbor couplings emerge as a result of high-order tunneling, lifting the Majorana zero energy at the sweet spot. This energy splitting is mitigated in a longer chain, approaching topological protection. Our proposal has two immediate advantages: obtaining a larger energy gap from direct tunneling, and creating a Kitaev chain using a reduced number of quantum dots and hybrid segments.
{"title":"Kitaev chain in an alternating quantum dot-Andreev bound state array","authors":"Sebastian Miles, David van Driel, Michael Wimmer, Chun-Xiao Liu","doi":"10.1103/physrevb.110.024520","DOIUrl":"https://doi.org/10.1103/physrevb.110.024520","url":null,"abstract":"We propose to implement a Kitaev chain based on an array of alternating normal and superconductor hybrid quantum dots embedded in semiconductors. In particular, the orbitals in the dot and the Andreev bound states in the hybrid are now on an equal footing, and both emerge as low-energy degrees of freedom in the Kitaev chain, with the couplings being induced by direct tunneling. Due to the electron and hole components in the Andreev bound state, this coupling is simultaneously of the normal and Andreev types, with their ratio being tunable by varying one or several of the experimentally accessible physical parameters, e.g., strength and direction of the Zeeman field, as well as changing the proximity effect on the normal quantum dots. As such, it becomes feasible to realize a two-site Kitaev chain in a simple setup with only one normal quantum dot and one hybrid segment. Interestingly, when scaling up the system to a three-site Kitaev chain, next-nearest-neighbor couplings emerge as a result of high-order tunneling, lifting the Majorana zero energy at the sweet spot. This energy splitting is mitigated in a longer chain, approaching topological protection. Our proposal has two immediate advantages: obtaining a larger energy gap from direct tunneling, and creating a Kitaev chain using a reduced number of quantum dots and hybrid segments.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141794742","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 : 2024-07-30DOI: 10.1103/physrevb.110.014520
Hiroto Tanaka, Hikaru Watanabe, Youichi Yanase
Noncentrosymmetric superconductors offer fascinating phenomena of quantum transport and optics such as nonreciprocal and nonlinear responses. Time-reversal symmetry breaking often plays an essential role in the emergence and enhancement of nonreciprocal transport. In this paper, we show the nonreciprocal optical responses in noncentrosymmetric superconductors arising from time-reversal symmetry breaking by demonstrating them in -wave superconductors with a Rashba spin-orbit coupling and a magnetic field. Numerical results reveal the superconductivity-induced bulk photocurrent and second harmonic generation, which are forbidden at the zero magnetic field. We discuss the properties and mechanisms of the superconducting nonlinear responses emerging under the magnetic field. In particular, we investigate the magnetic field dependence of the photocurrent conductivity and clarify the essential ingredients, which give a contribution unique to superconductors under the magnetic field. This contribution is dominant in the low-carrier-density regime although the corresponding joint density of state is tiny. We attribute the enhancement to the quantum geometry. Moreover, the nonlinear conductivity shows peculiar sign reversal at the transition to the topological superconducting state. We propose a bulk probe of topological transition and quantum geometry in superconductors.
非中心对称超导体具有迷人的量子传输和光学现象，例如非互惠和非线性响应。在非互惠输运的出现和增强过程中，时间反向对称破缺往往起着至关重要的作用。在本文中，我们通过在具有拉什巴自旋轨道耦合和磁场的 s 波超导体中演示由时间反向对称性破缺引起的非互易光学响应。数值结果揭示了超导性诱导的体光电流和二次谐波生成，它们在零磁场下是被禁止的。我们讨论了磁场下出现的超导非线性响应的特性和机制。特别是，我们研究了光电流传导性的磁场依赖性，并阐明了在磁场下超导体特有的基本成分。虽然相应的联合状态密度很小，但这种贡献在低载流子密度体系中占主导地位。我们将这种增强归因于量子几何。此外，在过渡到拓扑超导态时，非线性电导率显示出奇特的符号反转。我们提出了超导体中拓扑转变和量子几何的体探测器。
{"title":"Nonlinear optical response in superconductors in magnetic field: Quantum geometry and topological superconductivity","authors":"Hiroto Tanaka, Hikaru Watanabe, Youichi Yanase","doi":"10.1103/physrevb.110.014520","DOIUrl":"https://doi.org/10.1103/physrevb.110.014520","url":null,"abstract":"Noncentrosymmetric superconductors offer fascinating phenomena of quantum transport and optics such as nonreciprocal and nonlinear responses. Time-reversal symmetry breaking often plays an essential role in the emergence and enhancement of nonreciprocal transport. In this paper, we show the nonreciprocal optical responses in noncentrosymmetric superconductors arising from time-reversal symmetry breaking by demonstrating them in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>s</mi></math>-wave superconductors with a Rashba spin-orbit coupling and a magnetic field. Numerical results reveal the superconductivity-induced bulk photocurrent and second harmonic generation, which are forbidden at the zero magnetic field. We discuss the properties and mechanisms of the superconducting nonlinear responses emerging under the magnetic field. In particular, we investigate the magnetic field dependence of the photocurrent conductivity and clarify the essential ingredients, which give a contribution unique to superconductors under the magnetic field. This contribution is dominant in the low-carrier-density regime although the corresponding joint density of state is tiny. We attribute the enhancement to the quantum geometry. Moreover, the nonlinear conductivity shows peculiar sign reversal at the transition to the topological superconducting state. We propose a bulk probe of topological transition and quantum geometry in superconductors.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141794593","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 : 2024-07-30DOI: 10.1103/physrevb.110.014521
L. Attias, K. Michaeli, M. Khodas
We investigate the planar Hall effect (PHE) in two-dimensional (2D) superconductors with spin-orbit interactions, where transport anisotropy is induced by an in-plane magnetic field. While PHE typically arises from the breaking of basal mirror symmetry, when the field exclusively couples to spin degrees of freedom, it remains negligible in noninteracting systems. In this study, we explore anisotropic paraconductivity as an alternative mechanism for PHE observed in 2D superconductors in the normal state. Due to the momentum dependence of spin-orbit interactions, the field-induced pair breaking exhibits anisotropy. To elucidate this phenomenon, we compute the PHE for the Rashba spin-orbit interaction. Our analysis reveals that Cooper pairs propagating along the field experience stronger pair breaking compared to those moving perpendicular to the field. This physical insight is corroborated by explicit calculations of paraconductivity.
{"title":"Planar Hall effect from superconducting fluctuations","authors":"L. Attias, K. Michaeli, M. Khodas","doi":"10.1103/physrevb.110.014521","DOIUrl":"https://doi.org/10.1103/physrevb.110.014521","url":null,"abstract":"We investigate the planar Hall effect (PHE) in two-dimensional (2D) superconductors with spin-orbit interactions, where transport anisotropy is induced by an in-plane magnetic field. While PHE typically arises from the breaking of basal mirror symmetry, when the field exclusively couples to spin degrees of freedom, it remains negligible in noninteracting systems. In this study, we explore anisotropic paraconductivity as an alternative mechanism for PHE observed in 2D superconductors in the normal state. Due to the momentum dependence of spin-orbit interactions, the field-induced pair breaking exhibits anisotropy. To elucidate this phenomenon, we compute the PHE for the Rashba spin-orbit interaction. Our analysis reveals that Cooper pairs propagating along the field experience stronger pair breaking compared to those moving perpendicular to the field. This physical insight is corroborated by explicit calculations of paraconductivity.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141794594","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 : 2024-07-30DOI: 10.1103/physrevb.110.045444
S. M. Rafi-Ul-Islam, Zhuo Bin Siu, Md. Saddam Hossain Razo, Haydar Sahin, Mansoor B. A. Jalil
We present a study of complex energy braiding in a one-dimensional non-Hermitian system with -order long-range asymmetrical coupling. Our work highlights the emergence of novel topological phenomena in such systems beyond the conventional nearest-neighbor interaction. The modified SSH model displays distinct knot and link combinations in the complex energy-momentum space under periodic boundary conditions, which can be controlled by varying the coupling strengths. A topological invariant, namely the braiding index, is introduced to characterize the different complex energy braiding profiles, which depends on the zeros and poles of the characteristic polynomials. Furthermore, we demonstrate that the non-Hermitian skin effect can be localized at one or both ends, signifying conventional or bipolar localization, depending on the sign of the braiding index. Phase transitions between different braiding phases with the same (opposite) sign of the topological invariant occur at Type-1 (Type-2) exceptional points, with Type-1 (Type-2) phase transitions accompanied by single (multiple) exceptional points. We propose an experimental setup to realize the various braiding schemes based on the RLC circuit framework, which provides an accessible avenue for implementation without recourse to high-dimensional momentum space required in most other platforms.
{"title":"From knots to exceptional points: Emergence of topological features in non-Hermitian systems with long-range coupling","authors":"S. M. Rafi-Ul-Islam, Zhuo Bin Siu, Md. Saddam Hossain Razo, Haydar Sahin, Mansoor B. A. Jalil","doi":"10.1103/physrevb.110.045444","DOIUrl":"https://doi.org/10.1103/physrevb.110.045444","url":null,"abstract":"We present a study of complex energy braiding in a one-dimensional non-Hermitian system with <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>n</mi><mi>th</mi></mrow></math>-order long-range asymmetrical coupling. Our work highlights the emergence of novel topological phenomena in such systems beyond the conventional nearest-neighbor interaction. The modified SSH model displays <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>n</mi></math> distinct knot and link combinations in the complex energy-momentum space under periodic boundary conditions, which can be controlled by varying the coupling strengths. A topological invariant, namely the braiding index, is introduced to characterize the different complex energy braiding profiles, which depends on the zeros and poles of the characteristic polynomials. Furthermore, we demonstrate that the non-Hermitian skin effect can be localized at one or both ends, signifying conventional or bipolar localization, depending on the sign of the braiding index. Phase transitions between different braiding phases with the same (opposite) sign of the topological invariant occur at Type-1 (Type-2) exceptional points, with Type-1 (Type-2) phase transitions accompanied by single (multiple) exceptional points. We propose an experimental setup to realize the various braiding schemes based on the RLC circuit framework, which provides an accessible avenue for implementation without recourse to high-dimensional momentum space required in most other platforms.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141794745","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}
Nonequilibrium molecular dynamics simulations were carried out to explore the coupling behaviors of spallation and microjetting in single-crystal (SC) and nanocrystalline (NC) Al at the atomic scale. Both SC and NC models exhibited void collapse, serving as an indispensable element complementary to the classical ductile fracture mechanisms dominated by nucleation, growth, and coalescence. Two representative mechanisms—compressive collapse and spontaneous collapse—were uncovered, with a unique behavior in which a coalesced void also collapsed. It was also discovered that the spallation might either cause the microjet to disappear or accelerate fragmentation, with the disappearance effectuating a peculiar transformation from coexisting spallation and microjetting to pure spallation. The difference between SC and NC microjetting models residing in that grain boundary not only caused a larger peak velocity of the spike tip due to the inhomogeneous deformation but also restrained the Richtmyer-Meshkov instability growth to some extent owing to energy dissipation. The jet sheet fragmentation was attributed to three mechanisms: void nucleation, growth, and coalescence for the jet body; longitudinal necking induced by the tensile stress for the residual one-dimensional jet body; and transverse necking induced by the shear and tensile stresses for the jet head.
{"title":"Coupling of spallation and microjetting in aluminum at the atomic scale","authors":"Xin Yang, Yu Tian, Han Zhao, Fang Wang, Lusheng Wang, Moujin Lin, Peng Wen, Wenjun Chen","doi":"10.1103/physrevb.110.024113","DOIUrl":"https://doi.org/10.1103/physrevb.110.024113","url":null,"abstract":"Nonequilibrium molecular dynamics simulations were carried out to explore the coupling behaviors of spallation and microjetting in single-crystal (SC) and nanocrystalline (NC) Al at the atomic scale. Both SC and NC models exhibited void collapse, serving as an indispensable element complementary to the classical ductile fracture mechanisms dominated by nucleation, growth, and coalescence. Two representative mechanisms—compressive collapse and spontaneous collapse—were uncovered, with a unique behavior in which a coalesced void also collapsed. It was also discovered that the spallation might either cause the microjet to disappear or accelerate fragmentation, with the disappearance effectuating a peculiar transformation from coexisting spallation and microjetting to pure spallation. The difference between SC and NC microjetting models residing in that grain boundary not only caused a larger peak velocity of the spike tip due to the inhomogeneous deformation but also restrained the Richtmyer-Meshkov instability growth to some extent owing to energy dissipation. The jet sheet fragmentation was attributed to three mechanisms: void nucleation, growth, and coalescence for the jet body; longitudinal necking induced by the tensile stress for the residual one-dimensional jet body; and transverse necking induced by the shear and tensile stresses for the jet head.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141794595","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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