Pub Date : 2024-07-26DOI: 10.1103/physrevb.110.035429
Mohammad Ali Mohebpour, Sahar Izadi Vishkayi, Valerio Vitale, Nicola Seriani, Meysam Bagheri Tagani
The existence of a flat band near the Fermi level can be a suitable platform for the emergence of interesting phenomena in condensed matter physics. Recently, monolayer has been experimentally synthesized [Q. Guo et al., Nature (London)613, 53 (2023)], which has a flat and isolated valence band. Motivated by the recent experiment, we investigate the origin of the flat band as well as the electronic, optical, photocatalytic, and magnetic properties of the monolayer by combining density functional theory and many-body quantum perturbation theory. Our results show that the flat and isolated band of this monolayer is caused by the interplay between the Peierls distortion and the electronic configuration of Nb atoms. We show that monolayers based on other elements of group 5 of the periodic table, including the V and Ta atoms, also have a flat band. The investigation of the bandwidth of the monolayer under the biaxial and uniaxial strains reveals that this material can be grown on substrates with a larger lattice constant by maintaining the flat band. Examining the material's response to the linearly polarized light not only reveals the presence of weak optical anisotropy, but also shows the existence of a bright exciton with a binding energy of about 0.94 eV. Hole doping can result in a flat-band-induced phase transition from semiconductor to ferromagnet. By adjusting the amount of doping, a bipolar magnetic semiconductor or a half metal can be created. The interaction between the nearest Nb atoms is ferromagnetic, while an antiferromagnetic interaction appears between the second neighbors, which grows significantly with increasing doping. Our results demonstrate that monolayer has a suitable potential for spintronic applications in addition to electronic and optoelectronic applications.
费米级附近平坦价带的存在可以为凝聚态物理中有趣现象的出现提供一个合适的平台。最近，实验合成了 NbOCl2 单层[Q. Guo 等，Nature (London) 613, 53 (2023)]，它具有平坦而孤立的价带。受最近实验的启发，我们结合密度泛函理论和多体量子扰动理论，研究了平坦价带的起源以及单层的电子、光学、光催化和磁学性质。我们的研究结果表明，该单层的平坦隔离带是由 Peierls 扭曲和铌原子电子构型之间的相互作用造成的。我们的研究表明，基于周期表第 5 族其他元素（包括 V 原子和 Ta 原子）的单层也具有平坦带。通过研究单层材料在双轴和单轴应变下的带宽，我们发现这种材料可以在晶格常数较大的基底上生长，从而保持平带。研究该材料对线性偏振光的响应，不仅可以发现存在微弱的光学各向异性，还可以发现存在结合能约为 0.94 eV 的明亮激子。空穴掺杂可导致从半导体到铁磁体的平带诱导相变。通过调整掺杂量，可以产生双极磁性半导体或半金属。最近的铌原子之间的相互作用是铁磁性的，而第二相邻原子之间的相互作用则是反铁磁性的，这种相互作用随着掺杂量的增加而显著增强。我们的研究结果表明，除电子和光电应用外，NbOCl2 单层还具有自旋电子应用的潜力。
{"title":"Origin and properties of the flat band in monolayer NbOCl2","authors":"Mohammad Ali Mohebpour, Sahar Izadi Vishkayi, Valerio Vitale, Nicola Seriani, Meysam Bagheri Tagani","doi":"10.1103/physrevb.110.035429","DOIUrl":"https://doi.org/10.1103/physrevb.110.035429","url":null,"abstract":"The existence of a flat band near the Fermi level can be a suitable platform for the emergence of interesting phenomena in condensed matter physics. Recently, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>NbOCl</mi><mn>2</mn></msub></math> monolayer has been experimentally synthesized [Q. Guo <i>et al.</i>, <span>Nature (London)</span> <b>613</b>, 53 (2023)], which has a flat and isolated valence band. Motivated by the recent experiment, we investigate the origin of the flat band as well as the electronic, optical, photocatalytic, and magnetic properties of the monolayer by combining density functional theory and many-body quantum perturbation theory. Our results show that the flat and isolated band of this monolayer is caused by the interplay between the Peierls distortion and the electronic configuration of Nb atoms. We show that monolayers based on other elements of group 5 of the periodic table, including the V and Ta atoms, also have a flat band. The investigation of the bandwidth of the monolayer under the biaxial and uniaxial strains reveals that this material can be grown on substrates with a larger lattice constant by maintaining the flat band. Examining the material's response to the linearly polarized light not only reveals the presence of weak optical anisotropy, but also shows the existence of a bright exciton with a binding energy of about 0.94 eV. Hole doping can result in a flat-band-induced phase transition from semiconductor to ferromagnet. By adjusting the amount of doping, a bipolar magnetic semiconductor or a half metal can be created. The interaction between the nearest Nb atoms is ferromagnetic, while an antiferromagnetic interaction appears between the second neighbors, which grows significantly with increasing doping. Our results demonstrate that <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>NbOCl</mi><mn>2</mn></msub></math> monolayer has a suitable potential for spintronic applications in addition to electronic and optoelectronic applications.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764263","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 : 2024-07-26DOI: 10.1103/physrevb.110.045148
Koyena Bose, Ajit C. Balram
Fractional quantum Hall (FQH) fluids host quasiparticle excitations that carry a fraction of the electronic charge. Moreover, in contrast to bosons and fermions that carry exchange statistics of 0 and respectively, these quasiparticles of FQH fluids, when braided around one another, can accumulate a Berry phase, which is a fractional multiple of . Deploying the spherical geometry, we numerically demonstrate that composite fermion particle (CFP) excitations in the Jain FQH states carry Abelian fractional statistics. Previously, the exchange statistics of CFPs were studied in the disk geometry, where the statistics get obscured due to a shift in the phase arising from the addition of another CFP, making its determination cumbersome without prior knowledge of the shift. We show that on the sphere this technical issue can be circumvented and the statistics of CFPs can be obtained more transparently. The ideas we present can be extended to determine the statistics of quasiparticles arising in certain non-Abelian partonic FQH states.
{"title":"Numerical demonstration of Abelian fractional statistics of composite fermion excitations in the spherical geometry","authors":"Koyena Bose, Ajit C. Balram","doi":"10.1103/physrevb.110.045148","DOIUrl":"https://doi.org/10.1103/physrevb.110.045148","url":null,"abstract":"Fractional quantum Hall (FQH) fluids host quasiparticle excitations that carry a fraction of the electronic charge. Moreover, in contrast to bosons and fermions that carry exchange statistics of 0 and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>π</mi></math> respectively, these quasiparticles of FQH fluids, when braided around one another, can accumulate a Berry phase, which is a fractional multiple of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>π</mi></math>. Deploying the spherical geometry, we numerically demonstrate that composite fermion particle (CFP) excitations in the Jain FQH states carry Abelian fractional statistics. Previously, the exchange statistics of CFPs were studied in the disk geometry, where the statistics get obscured due to a shift in the phase arising from the addition of another CFP, making its determination cumbersome without prior knowledge of the shift. We show that on the sphere this technical issue can be circumvented and the statistics of CFPs can be obtained more transparently. The ideas we present can be extended to determine the statistics of quasiparticles arising in certain non-Abelian partonic FQH states.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764280","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 : 2024-07-26DOI: 10.1103/physrevb.110.l041120
Bo Chen, Hao Liu, Qi-Yi Wu, Chen Zhang, Xue-Qing Ye, Yin-Zou Zhao, Jiao-Jiao Song, Xin-Yi Tian, Ba-Lei Tan, Zheng-Tai Liu, Mao Ye, Zhen-Hua Chen, Yao-Bo Huang, Da-Wei Shen, Ya-Hua Yuan, Jun He, Yu-Xia Duan, Jian-Qiao Meng
In this Letter, we investigate the electronic structure of a spin-triplet superconductor candidate using high-resolution angle-resolved photoemission spectroscopy and density functional theory calculations. Notably, possible Fermi surface nesting hints at connections to magnetic excitation or quadrupole density wave phenomena, elucidating the superconducting mechanisms. Measured band structures reveal primarily localized electrons, with minor itinerant contributions. Additionally, a transition from localized to itinerant behavior and significant hybridization anisotropy underscore the role of electrons in shaping electronic properties. These findings deepen our understanding of 's unconventional superconductivity and magnetism. Further exploration promises advances in superconductivity research.
在这封信中，我们利用高分辨率角分辨光发射光谱和密度泛函理论计算，研究了自旋三重超导体候选物质 CeRh2As2 的电子结构。值得注意的是，可能的费米面嵌套暗示了与磁激发或四极密度波现象的联系，从而阐明了超导机制。测量到的能带结构显示，4f 电子主要是局域化的，只有少量的流动电子。此外，从局部行为到巡回行为的转变以及显著的 c-f 杂化各向异性突出了 f 电子在塑造电子特性方面的作用。这些发现加深了我们对 CeRh2As2 的非传统超导性和磁性的理解。进一步的探索有望推动超导研究的发展。
{"title":"Exploring possible Fermi surface nesting and the nature of heavy quasiparticles in the spin-triplet superconductor candidate CeRh2As2","authors":"Bo Chen, Hao Liu, Qi-Yi Wu, Chen Zhang, Xue-Qing Ye, Yin-Zou Zhao, Jiao-Jiao Song, Xin-Yi Tian, Ba-Lei Tan, Zheng-Tai Liu, Mao Ye, Zhen-Hua Chen, Yao-Bo Huang, Da-Wei Shen, Ya-Hua Yuan, Jun He, Yu-Xia Duan, Jian-Qiao Meng","doi":"10.1103/physrevb.110.l041120","DOIUrl":"https://doi.org/10.1103/physrevb.110.l041120","url":null,"abstract":"In this Letter, we investigate the electronic structure of a spin-triplet superconductor candidate <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">CeRh</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">As</mi><mn>2</mn></msub></math> using high-resolution angle-resolved photoemission spectroscopy and density functional theory calculations. Notably, possible Fermi surface nesting hints at connections to magnetic excitation or quadrupole density wave phenomena, elucidating the superconducting mechanisms. Measured band structures reveal primarily localized <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>4</mn><mi>f</mi></mrow></math> electrons, with minor itinerant contributions. Additionally, a transition from localized to itinerant behavior and significant <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>c</mi><mtext>−</mtext><mi>f</mi></mrow></math> hybridization anisotropy underscore the role of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>f</mi></math> electrons in shaping electronic properties. These findings deepen our understanding of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">CeRh</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">As</mi><mn>2</mn></msub></math>'s unconventional superconductivity and magnetism. Further exploration promises advances in superconductivity research.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764266","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 : 2024-07-26DOI: 10.1103/physrevb.110.045442
Federico Escudero
We develop a diagrammatic perturbation theory to account for the emergence of moiré bands in the continuum model of twisted bilayer graphene. Our framework is build on treating the moiré potential as a perturbation that transfers electrons from one layer to another through the exchange of the three wave vectors that define the moiré Brillouin zone. By working in the two-band basis of each monolayer, we analyze the one-particle Green's function and introduce a diagrammatic representation for the scattering processes. We then identify the moiré-induced self-energy, relate it to the quasiparticle weight and velocity of the moiré bands, and show how it can be obtained by summing irreducible diagrams. We also connect the emergence of flat bands to the behavior of the static self-energy at the magic angle. In particular, we show that a vanishing Dirac velocity is a direct consequence of the relative orientation of the momentum transfer vectors, suggesting that the origin of magic angles in twisted bilayer graphene is intrinsically connected to its geometrical properties. Our approach provides a diagrammatic framework that highlights the physical properties of the moiré bands.
{"title":"Diagrammatic perturbation approach to moiré bands in twisted bilayer graphene","authors":"Federico Escudero","doi":"10.1103/physrevb.110.045442","DOIUrl":"https://doi.org/10.1103/physrevb.110.045442","url":null,"abstract":"We develop a diagrammatic perturbation theory to account for the emergence of moiré bands in the continuum model of twisted bilayer graphene. Our framework is build on treating the moiré potential as a perturbation that transfers electrons from one layer to another through the exchange of the three wave vectors that define the moiré Brillouin zone. By working in the two-band basis of each monolayer, we analyze the one-particle Green's function and introduce a diagrammatic representation for the scattering processes. We then identify the moiré-induced self-energy, relate it to the quasiparticle weight and velocity of the moiré bands, and show how it can be obtained by summing irreducible diagrams. We also connect the emergence of flat bands to the behavior of the static self-energy at the magic angle. In particular, we show that a vanishing Dirac velocity is a direct consequence of the relative orientation of the momentum transfer vectors, suggesting that the origin of magic angles in twisted bilayer graphene is intrinsically connected to its geometrical properties. Our approach provides a diagrammatic framework that highlights the physical properties of the moiré bands.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764264","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 : 2024-07-26DOI: 10.1103/physrevb.110.035428
Leonard Dobrzyński, Housni Al-Wahsh, Abdellatif Akjouj, Eman A. Abdel-Ghaffar
A. bound state eigenfunction is defined here to be strictly localized within a subspace of the structure under study and has no decreasing behavior. Its eigenwavelength can be within state continua. Bound states in the continuum (BICs) and long-lived resonances have become a unique way to produce the extreme localization of electronic waves. We present a theoretical and numerical demonstration of semi-infinite bound states in the continuum (SIBICs) and long-lived resonances in a ringlike electronic microresonator coupled to a finite stub and to two electronic rib/ridge waveguides, together with their existence conditions. This structure is composed of a closed loop of length , a finite stub of length and two semi-infinite leads. SIBICs localized in a semi-infinite subspace domain induce transmission zeros. Others induce transmission ones in the middle of long-lived resonances. The BICs correspond to localized resonances of infinite lifetime inside the structure, without any leakage into the surrounding leads. When BICs exist within state continua, they induce Fano resonances exhibiting sharp peaks in the transmission spectra and in the variation of the density of states for specific values of the stub length . This enables one to regulate these resonances by means of this length. The obtained results take due account of the state number conservation between the final system and the reference one. This conservation rule enables one to find all the states of the final system and among them the bound in the continuum ones. The analytical results are obtained by means of the Green's function technique. The structures and the long-lived resonances presented in this paper may have potential applications due to their high sensitivities to weak perturbations, in particular in sensing, wave filtering, and microelectronic devices.
{"title":"Bound states in the continuum and long-lived electronic resonances in mesoscopic structures","authors":"Leonard Dobrzyński, Housni Al-Wahsh, Abdellatif Akjouj, Eman A. Abdel-Ghaffar","doi":"10.1103/physrevb.110.035428","DOIUrl":"https://doi.org/10.1103/physrevb.110.035428","url":null,"abstract":"A. bound state eigenfunction is defined here to be strictly localized within a subspace of the structure under study and has no decreasing behavior. Its eigenwavelength can be within state continua. Bound states in the continuum (BICs) and long-lived resonances have become a unique way to produce the extreme localization of electronic waves. We present a theoretical and numerical demonstration of semi-infinite bound states in the continuum (SIBICs) and long-lived resonances in a ringlike electronic microresonator coupled to a finite stub and to two electronic rib/ridge waveguides, together with their existence conditions. This structure is composed of a closed loop of length <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>L</mi></math>, a finite stub of length <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>L</mi><mn>1</mn></msub></math> and two semi-infinite leads. SIBICs localized in a semi-infinite subspace domain induce transmission zeros. Others induce transmission ones in the middle of long-lived resonances. The BICs correspond to localized resonances of infinite lifetime inside the structure, without any leakage into the surrounding leads. When BICs exist within state continua, they induce Fano resonances exhibiting sharp peaks in the transmission spectra and in the variation of the density of states for specific values of the stub length <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>L</mi><mn>1</mn></msub></math>. This enables one to regulate these resonances by means of this length. The obtained results take due account of the state number conservation between the final system and the reference one. This conservation rule enables one to find all the states of the final system and among them the bound in the continuum ones. The analytical results are obtained by means of the Green's function technique. The structures and the long-lived resonances presented in this paper may have potential applications due to their high sensitivities to weak perturbations, in particular in sensing, wave filtering, and microelectronic devices.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764267","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 : 2024-07-25DOI: 10.1103/physrevb.110.014208
Mrinal Sarkar, Tilman Enss, Nicolò Defenu
We investigate the role of the spectral dimension in determining the universality of phase transitions on a complex network. Due to its structural heterogeneity, a complex network generally acts as a disordered system. Specifically, we study the synchronization and entrainment transitions in the nonequilibrium dynamics of the Kuramoto model and the phase transition of the equilibrium dynamics of the classical model, thereby covering a broad spectrum from nonlinear dynamics to statistical and condensed matter physics. Using linear theory, we obtain a general relationship between the dynamics occurring on the network and the underlying network properties. This yields the lower critical spectral dimension of the phase synchronization and entrainment transitions in the Kuramoto model as and , respectively, whereas for the phase transition in the model it is . To test our theoretical hypotheses, we employ a network where any two nodes on the network are connected with a probability proportional to a power law of the distance between the nodes; this realizes any desired . Our detailed numerical study agrees well with the prediction of linear theory for the phase synchronization transition in the Kuramoto model. However, it shows a clear entrainment transition in the Kuramoto model and phase transition in the model at , not as predicted by linear theory. Our study indicates that network disorder in the region introduces strong finite-size fluctuations, which makes it extremely difficult to probe the existence of the ordered phase as predicted, affecting the dynamics profoundly.
{"title":"Universality of critical dynamics on a complex network","authors":"Mrinal Sarkar, Tilman Enss, Nicolò Defenu","doi":"10.1103/physrevb.110.014208","DOIUrl":"https://doi.org/10.1103/physrevb.110.014208","url":null,"abstract":"We investigate the role of the spectral dimension <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>d</mi><mi>s</mi></msub></math> in determining the universality of phase transitions on a complex network. Due to its structural heterogeneity, a complex network generally acts as a disordered system. Specifically, we study the synchronization and entrainment transitions in the nonequilibrium dynamics of the Kuramoto model and the phase transition of the equilibrium dynamics of the classical <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>X</mi><mi>Y</mi></mrow></math> model, thereby covering a broad spectrum from nonlinear dynamics to statistical and condensed matter physics. Using linear theory, we obtain a general relationship between the dynamics occurring on the network and the underlying network properties. This yields the lower critical spectral dimension of the phase synchronization and entrainment transitions in the Kuramoto model as <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>d</mi><mi>s</mi></msub><mo>=</mo><mn>4</mn></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>d</mi><mi>s</mi></msub><mo>=</mo><mn>2</mn></mrow></math>, respectively, whereas for the phase transition in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>X</mi><mi>Y</mi></mrow></math> model it is <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>d</mi><mi>s</mi></msub><mo>=</mo><mn>2</mn></mrow></math>. To test our theoretical hypotheses, we employ a network where any two nodes on the network are connected with a probability proportional to a power law of the distance between the nodes; this realizes any desired <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>d</mi><mi>s</mi></msub><mo>∈</mo><mrow><mo>[</mo><mn>1</mn><mo>,</mo><mi>∞</mi><mo>)</mo></mrow></mrow></math>. Our detailed numerical study agrees well with the prediction of linear theory for the phase synchronization transition in the Kuramoto model. However, it shows a clear entrainment transition in the Kuramoto model and phase transition in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>X</mi><mi>Y</mi></mrow></math> model at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>d</mi><mi>s</mi></msub><mo>≳</mo><mn>3</mn></mrow></math>, not <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>d</mi><mi>s</mi></msub><mo>=</mo><mn>2</mn></mrow></math> as predicted by linear theory. Our study indicates that network disorder in the region <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>2</mn><mo>≤</mo><msub><mi>d</mi><mi>s</mi></msub><mo>≲</mo><mn>3</mn></mrow></math> introduces strong finite-size fluctuations, which makes it extremely difficult to probe the existence of the ordered phase as predicted, affecting the dynamics profoundly.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764018","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 : 2024-07-25DOI: 10.1103/physrevb.110.014437
Xin Hu, X. S. Wang, Zhenyu Wang
We theoretically investigated the antivortex stabilized by anisotropic Dzyaloshinskii-Moriya interaction (DMI) in nanodisks. Remarkably, we found that the antivortex remains stable even when the nanodisk radius is reduced to 15 nm. We also investigated the antivortex dynamics under a static in-plane magnetic field, which shows that the displacement of the antivortex core depends on its vorticity and helicity, providing a fundamental basis for distinguishing different vortex types. Additionally, spin-polarized currents can trigger a self-sustained gyration of the antivortex at low current densities, while inducing polarity switching at high current densities. Our findings offer valuable insights into the role of DMI in stabilizing topological solitons and their potential applications in spin-torque nano-oscillators and magnetic memories.
{"title":"Stabilization and dynamics of magnetic antivortices in a nanodisk with anisotropic Dzyaloshinskii-Moriya interaction","authors":"Xin Hu, X. S. Wang, Zhenyu Wang","doi":"10.1103/physrevb.110.014437","DOIUrl":"https://doi.org/10.1103/physrevb.110.014437","url":null,"abstract":"We theoretically investigated the antivortex stabilized by anisotropic Dzyaloshinskii-Moriya interaction (DMI) in nanodisks. Remarkably, we found that the antivortex remains stable even when the nanodisk radius is reduced to 15 nm. We also investigated the antivortex dynamics under a static in-plane magnetic field, which shows that the displacement of the antivortex core depends on its vorticity and helicity, providing a fundamental basis for distinguishing different vortex types. Additionally, spin-polarized currents can trigger a self-sustained gyration of the antivortex at low current densities, while inducing polarity switching at high current densities. Our findings offer valuable insights into the role of DMI in stabilizing topological solitons and their potential applications in spin-torque nano-oscillators and magnetic memories.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764168","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 : 2024-07-25DOI: 10.1103/physrevb.110.024429
Kiyu Fukui, Yasuyuki Kato, Yukitoshi Motome
Open quantum systems display unusual phenomena not seen in closed systems, such as new topological phases and unconventional phase transitions. An interesting example was studied for a quantum spin liquid in the Kitaev model [Phys. Rev. Lett.126, 077201 (2021)]; an effective non-Hermitian Kitaev model, which incorporates dissipation effects, was shown to give rise to a gapless spin liquid state with exceptional points in the Majorana dispersions. Given that an external magnetic field induces a gapped Majorana topological state in the Hermitian case, the exceptional points may bring about intriguing quantum phenomena under a magnetic field. Here we investigate the non-Hermitian Kitaev model perturbed by a magnetic field. We show that the exceptional points remain gapless up to a nonzero critical magnetic field, in stark contrast with the Hermitian case where an infinitesimal field opens a gap. The gapless state is stable over a wide range of the magnetic field for some particular parameter sets, and, in special cases, undergoes topological transitions to another gapless state with different winding number around the exceptional points without opening a gap. In addition, in the system with edges, we find that the non-Hermitian skin effect is induced by the magnetic field, even for the parameters where the skin effect is absent at zero field. The chirality of edge states is switched through the exceptional points, similarly to the surface Fermi arcs connected by the Weyl points in three-dimensional Weyl semimetals. Our results provide a new possible route to stabilize topological gapless quantum spin liquids under the magnetic field in the presence of dissipation.
{"title":"Magnetic field effects on the Kitaev model coupled to environment","authors":"Kiyu Fukui, Yasuyuki Kato, Yukitoshi Motome","doi":"10.1103/physrevb.110.024429","DOIUrl":"https://doi.org/10.1103/physrevb.110.024429","url":null,"abstract":"Open quantum systems display unusual phenomena not seen in closed systems, such as new topological phases and unconventional phase transitions. An interesting example was studied for a quantum spin liquid in the Kitaev model [<span>Phys. Rev. Lett.</span> <b>126</b>, 077201 (2021)]; an effective non-Hermitian Kitaev model, which incorporates dissipation effects, was shown to give rise to a gapless spin liquid state with exceptional points in the Majorana dispersions. Given that an external magnetic field induces a gapped Majorana topological state in the Hermitian case, the exceptional points may bring about intriguing quantum phenomena under a magnetic field. Here we investigate the non-Hermitian Kitaev model perturbed by a magnetic field. We show that the exceptional points remain gapless up to a nonzero critical magnetic field, in stark contrast with the Hermitian case where an infinitesimal field opens a gap. The gapless state is stable over a wide range of the magnetic field for some particular parameter sets, and, in special cases, undergoes topological transitions to another gapless state with different winding number around the exceptional points without opening a gap. In addition, in the system with edges, we find that the non-Hermitian skin effect is induced by the magnetic field, even for the parameters where the skin effect is absent at zero field. The chirality of edge states is switched through the exceptional points, similarly to the surface Fermi arcs connected by the Weyl points in three-dimensional Weyl semimetals. Our results provide a new possible route to stabilize topological gapless quantum spin liquids under the magnetic field in the presence of dissipation.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764173","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}
Chalcogenide perovskite materials have been shown to exhibit excellent properties for optoelectronics and photovoltaics. The research, however, has been focused on the II-IV- series of compounds. Here, by theoretical calculation, we predict that in the III-III- perovskites, there could exist a transition between the indirect and direct band gaps induced by the coupling strength of the orbitals between the A-site and B-site cations. We validate this prediction by synthesizing through solid state reaction from three elemental materials. Micro-Raman analysis combined with Raman tensor calculations are used to identify the perovskite phase of micrometer-size grains, from which photoluminescence can be observed. The emitted light peaks at about 519 nm (or 2.39 eV), which corresponds to the largest band gap among the sulfide perovskites. The discovery of light-emitting enriches the family of chalcogenide perovskites for optoelectronic applications.
钙钛矿包晶材料在光电子学和光伏学方面表现出卓越的性能。然而，相关研究主要集中在 II-IV-S3 系列化合物上。在此，我们通过理论计算预测，在 III-III-S3 型透光石中，可能存在由 A 位和 B 位阳离子之间的 d 轨道耦合强度引起的间接带隙和直接带隙之间的转变。我们通过固态反应从三种元素材料合成了 LaScS3，从而验证了这一预测。通过微拉曼分析和拉曼张量计算，我们确定了微米大小晶粒的包晶相，并从中观察到了光致发光。发出的光在大约 519 nm（或 2.39 eV）处达到峰值，这与硫化物类包晶石中最大的带隙相对应。发光 LaScS3 的发现丰富了用于光电应用的铬化包晶家族。
{"title":"Indirect-to-direct band gap transition induced by d−d coupling between cations in rare-earth chalcogenide perovskites","authors":"Han Zhang, Yichun Pan, Zexin Liu, Biao Zeng, Xiaowei Wu, Chen Ming, Guoqing Xin, Weihang Zhou, Hao Zeng, Shengbai Zhang, Yi-Yang Sun","doi":"10.1103/physrevb.110.l041201","DOIUrl":"https://doi.org/10.1103/physrevb.110.l041201","url":null,"abstract":"Chalcogenide perovskite materials have been shown to exhibit excellent properties for optoelectronics and photovoltaics. The research, however, has been focused on the II-IV-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">S</mi><mn>3</mn></msub></math> series of compounds. Here, by theoretical calculation, we predict that in the III-III-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">S</mi><mn>3</mn></msub></math> perovskites, there could exist a transition between the indirect and direct band gaps induced by the coupling strength of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>d</mi></math> orbitals between the A-site and B-site cations. We validate this prediction by synthesizing <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>LaScS</mi><mn>3</mn></msub></math> through solid state reaction from three elemental materials. Micro-Raman analysis combined with Raman tensor calculations are used to identify the perovskite phase of micrometer-size grains, from which photoluminescence can be observed. The emitted light peaks at about 519 nm (or 2.39 eV), which corresponds to the largest band gap among the sulfide perovskites. The discovery of light-emitting <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>LaScS</mi><mn>3</mn></msub></math> enriches the family of chalcogenide perovskites for optoelectronic applications.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764177","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 : 2024-07-25DOI: 10.1103/physrevb.110.024112
A. Sapkota, T. J. Slade, S. Huyan, N. K. Nepal, J. M. Wilde, N. Furukawa, S. H. Lapidus, L.-L. Wang, S. L. Bud'ko, P. C. Canfield
Single crystals of ( = Al, Ga, and In), belonging to the 1-5-1 family of compounds, were grown from a Pt-P solution at high temperatures, and measurements of the ambient pressure, temperature-dependent magnetization, resistivity, and x-ray diffraction were made. Additionally, the ambient-pressure Hall resistivity and temperature-dependent resistance under pressure were measured on . All three compounds have a tetragonal crystal structure at room temperature with metallic transport and weak diamagnetism over the 2–300 K temperature range. Surprisingly, at ambient pressure, both the transport and magnetization measurements on show a steplike feature in the 70–90 K region, suggesting a possible structural phase transition. Neither nor have any signatures of a phase transition in their temperature-dependent electrical resistance and magnetization data. Both the hysteretic nature and sharpness of the features in the data suggest that the transition is first-order. Single-crystal x-ray diffraction measurements provided further details of the structural transition with a possibility of a crystal symmetry different from below the transition temperature. The transition is characterized by anisotropic changes in the lattice parameters and a volume collapse with respect to the high-temperature tetragonal crystal structure. Furthermore, satellite peaks are observed at two distinct and nonequivalent wave vectors (0, 0, 0.5) and (0.5, 0.5, 0.5), and density functional theory calculations present phonon softening, especially at (0.5, 0.5, 0.5), as a possible driving mechanism. Additionally, we find that the structural transition temperature increases rapidly with increasing pressure, reaching room temperature by GPa, highlighting the high degree of pressure sensitivity of
{"title":"First-order structural phase transition at low temperature in GaPt5P and its rapid enhancement with pressure","authors":"A. Sapkota, T. J. Slade, S. Huyan, N. K. Nepal, J. M. Wilde, N. Furukawa, S. H. Lapidus, L.-L. Wang, S. L. Bud'ko, P. C. Canfield","doi":"10.1103/physrevb.110.024112","DOIUrl":"https://doi.org/10.1103/physrevb.110.024112","url":null,"abstract":"Single crystals of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>X</mi><msub><mi mathvariant=\"normal\">Pt</mi><mn>5</mn></msub><mtext>P</mtext></math> (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>X</mi></mrow></math> = Al, Ga, and In), belonging to the 1-5-1 family of compounds, were grown from a Pt-P solution at high temperatures, and measurements of the ambient pressure, temperature-dependent magnetization, resistivity, and x-ray diffraction were made. Additionally, the ambient-pressure Hall resistivity and temperature-dependent resistance under pressure were measured on <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>GaPt</mi><mn>5</mn></msub><mtext>P</mtext></math>. All three compounds have a tetragonal <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>P</mi><mn>4</mn><mo>/</mo><mi>m</mi><mi>m</mi><mi>m</mi></mrow></math> crystal structure at room temperature with metallic transport and weak diamagnetism over the 2–300 K temperature range. Surprisingly, at ambient pressure, both the transport and magnetization measurements on <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>GaPt</mi><mn>5</mn></msub><mtext>P</mtext></math> show a steplike feature in the 70–90 K region, suggesting a possible structural phase transition. Neither <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">AlPt</mi><mn>5</mn></msub><mtext>P</mtext></math> nor <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">InPt</mi><mn>5</mn></msub><mtext>P</mtext></math> have any signatures of a phase transition in their temperature-dependent electrical resistance and magnetization data. Both the hysteretic nature and sharpness of the features in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>GaPt</mi><mn>5</mn></msub><mtext>P</mtext></math> data suggest that the transition is first-order. Single-crystal x-ray diffraction measurements provided further details of the structural transition with a possibility of a crystal symmetry different from <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>P</mi><mn>4</mn><mo>/</mo><mi>m</mi><mi>m</mi><mi>m</mi></mrow></math> below the transition temperature. The transition is characterized by anisotropic changes in the lattice parameters and a volume collapse with respect to the high-temperature tetragonal crystal structure. Furthermore, satellite peaks are observed at two distinct and nonequivalent wave vectors (0, 0, 0.5) and (0.5, 0.5, 0.5), and density functional theory calculations present phonon softening, especially at (0.5, 0.5, 0.5), as a possible driving mechanism. Additionally, we find that the structural transition temperature increases rapidly with increasing pressure, reaching room temperature by <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>∼</mo><mn>2.2</mn></mrow></math> GPa, highlighting the high degree of pressure sensitivity of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><m","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141764176","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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