{"title":"Twist-angle transferable continuum model and second flat Chern band in twisted MoTe2 and WSe2","authors":"Xiao-Wei Zhang, Kaijie Yang, Chong Wang, Xiaoyu Liu, Ting Cao, Di Xiao","doi":"10.1038/s41535-025-00828-6","DOIUrl":"https://doi.org/10.1038/s41535-025-00828-6","url":null,"abstract":"","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"202 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145664772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-27DOI: 10.1038/s41535-025-00824-w
Jian Li, Shunjiao Li, Kai Liu, Xuyang Li, Linpeng Nie, Dan Zhao, Mengzhu Shi, Tao Wu, Xianhui Chen
Multi-orbital/band electronic structure and orbital-dependent electron correlations critically shape emergent electronic states in correlated materials. Bulk FeSe exemplifies this through its enigmatic nematic phase, whose microscopic mechanism remains an outstanding question. Here, we perform comprehensive 57 Fe and 77 Se nuclear magnetic resonance (NMR) study on the evolution of the nematicity of bulk FeSe under hydrostatic pressure. At low pressures, alongside the nematicity involving on-site 3 dxz /3 dyz orbital polarization, a distinct non-local $${d}_{{xy}}$$dxy nematicity emerges, indicating anisotropic intersite hopping of 3 dx y orbital electrons. With increasing pressure, while the on-site 3 dxz /3 dyz orbital polarization is gradually suppressed, the Lifshitz transition of the 3 dx y orbital hole pocket causes the $${d}_{{xy}}$$dxy nematicity transforms into a spin-driven Ising-type nematicity above a characteristic pressure. This Fermi-surface crossover also influences the superconducting transition temperature $${T}_{{rm{c}}}$$Tc , signifying the pivotal role of the more-correlated 3 dx y orbital in Cooper pairing at high pressures. Our results establish the orbital-selective nature of nematicity in FeSe and its nontrivial tunability via hydrostatic pressure. We demonstrate that nematicity serves as a sensitive indicator of the underlying electronic structure and interactions in correlated electron systems.
多轨道/带电子结构和轨道依赖的电子相关性对相关材料中的涌现电子态具有重要影响。散装FeSe通过其神秘的向列相证明了这一点，其微观机制仍然是一个悬而未决的问题。在这里，我们进行了全面的57 Fe和77 Se核磁共振（NMR）研究在静水压力下块状FeSe的向列性的演变。在低压下，除了涉及现场三维xz /三维yz轨道极化的向列外，还出现了明显的非局域$${d}_{{xy}}$$ d xy向列，表明三维xy轨道电子的各向异性跃迁。随着压力的增加，当现场三维xz /三维yz轨道极化逐渐被抑制时，三维xy轨道空穴的Lifshitz跃迁导致$${d}_{{xy}}$$ d xy向列在特征压力以上转变为自旋驱动的ising型向列。这种费米-表面交叉也影响超导转变温度$${T}_{{rm{c}}}$$ T c，这表明在高压下，更相关的三维x y轨道在库珀对中起着关键作用。我们的结果建立了FeSe中向列性的轨道选择性及其通过静水压力的非平凡可调性。我们证明了向列性可以作为相关电子系统中潜在电子结构和相互作用的敏感指标。
{"title":"Pressure-dependent orbital-selective nematicity in FeSe","authors":"Jian Li, Shunjiao Li, Kai Liu, Xuyang Li, Linpeng Nie, Dan Zhao, Mengzhu Shi, Tao Wu, Xianhui Chen","doi":"10.1038/s41535-025-00824-w","DOIUrl":"https://doi.org/10.1038/s41535-025-00824-w","url":null,"abstract":"Multi-orbital/band electronic structure and orbital-dependent electron correlations critically shape emergent electronic states in correlated materials. Bulk FeSe exemplifies this through its enigmatic nematic phase, whose microscopic mechanism remains an outstanding question. Here, we perform comprehensive <jats:sup>57</jats:sup> Fe and <jats:sup>77</jats:sup> Se nuclear magnetic resonance (NMR) study on the evolution of the nematicity of bulk FeSe under hydrostatic pressure. At low pressures, alongside the nematicity involving on-site 3 <jats:italic>d</jats:italic> <jats:sub> <jats:italic>xz</jats:italic> </jats:sub> /3 <jats:italic>d</jats:italic> <jats:sub>yz</jats:sub> orbital polarization, a distinct non-local <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${d}_{{xy}}$$</jats:tex-math> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>xy</mml:mi> </mml:mrow> </mml:msub> </mml:math> </jats:alternatives> </jats:inline-formula> nematicity emerges, indicating anisotropic intersite hopping of 3 <jats:italic>d</jats:italic> <jats:sub> <jats:italic>x</jats:italic> y </jats:sub> orbital electrons. With increasing pressure, while the on-site 3 <jats:italic>d</jats:italic> <jats:sub> <jats:italic>xz</jats:italic> </jats:sub> /3 <jats:italic>d</jats:italic> <jats:sub>yz</jats:sub> orbital polarization is gradually suppressed, the Lifshitz transition of the 3 <jats:italic>d</jats:italic> <jats:sub> <jats:italic>x</jats:italic> y </jats:sub> orbital hole pocket causes the <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${d}_{{xy}}$$</jats:tex-math> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>xy</mml:mi> </mml:mrow> </mml:msub> </mml:math> </jats:alternatives> </jats:inline-formula> nematicity transforms into a spin-driven Ising-type nematicity above a characteristic pressure. This Fermi-surface crossover also influences the superconducting transition temperature <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${T}_{{rm{c}}}$$</jats:tex-math> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> </mml:msub> </mml:math> </jats:alternatives> </jats:inline-formula> , signifying the pivotal role of the more-correlated 3 <jats:italic>d</jats:italic> <jats:sub> <jats:italic>x</jats:italic> y </jats:sub> orbital in Cooper pairing at high pressures. Our results establish the orbital-selective nature of nematicity in FeSe and its nontrivial tunability via hydrostatic pressure. We demonstrate that nematicity serves as a sensitive indicator of the underlying electronic structure and interactions in correlated electron systems.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"110 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145608803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1038/s41535-025-00819-7
Chris Halcrow, Ilya Shipulin, Federico Caglieris, Yongwei Li, Joachim Wosnitza, Hans-Henning Klauss, Sergei Zherlitsyn, Vadim Grinenko, Egor Babaev
Experiments have pointed to the formation of the electron quadrupling condensate in Ba 1− x K x Fe 2 As 2 at x ~ 0.8. The state spontaneously breaks time-reversal symmetry and is sandwiched between two critical points, separating it from the broken time-reversal symmetry (BTRS) superconducting state at $${T}_{{rm{c}}}^{U(1)}$$TcU(1) and a normal-metal state at $${T}_{{rm{c}}}^{{rm{Z2}}}$$TcZ2 . We report a theory of the acoustic effects spectroscopy of systems with an electron quadrupling phase based on ultrasound-velocity measurements. We show that the experimental results are consistent with BTRS superconductivity at x ~ 0.8, fulfilling the necessary condition for the formation of electron quadrupling in Ba 1− x K x Fe 2 As 2 . We provide the theoretical basis and the experimental strategy to study the order parameter symmetry of emerging quadrupling condensates in superconductors.
实验指出Ba 1−x K x fe2 As 2在x 0.8时形成了电子四倍凝聚。该状态自发地打破了时间反转对称，并夹在两个临界点之间，将其与时间反转对称（BTRS）超导态（$${T}_{{rm{c}}}^{U(1)}$$ t1 U(1)）和正常金属态（$${T}_{{rm{c}}}^{{rm{Z2}}}$$ t1 Z2）分开。我们报告了基于超声速度测量的电子四倍相系统的声效应光谱理论。我们发现实验结果与BTRS在x 0.8时的超导性一致，满足了Ba 1−x K x fe2 As 2中电子四重生成的必要条件。为研究超导体中新出现的四重凝聚体的序参量对称性提供了理论依据和实验策略。
{"title":"Ultrasound evidence for multicomponent superconducting order parameter in Ba1−xKxFe2As2 with electron quadrupling phase","authors":"Chris Halcrow, Ilya Shipulin, Federico Caglieris, Yongwei Li, Joachim Wosnitza, Hans-Henning Klauss, Sergei Zherlitsyn, Vadim Grinenko, Egor Babaev","doi":"10.1038/s41535-025-00819-7","DOIUrl":"https://doi.org/10.1038/s41535-025-00819-7","url":null,"abstract":"Experiments have pointed to the formation of the electron quadrupling condensate in Ba <jats:sub> 1− <jats:italic>x</jats:italic> </jats:sub> K <jats:sub> <jats:italic>x</jats:italic> </jats:sub> Fe <jats:sub>2</jats:sub> As <jats:sub>2</jats:sub> at <jats:italic>x</jats:italic> ~ 0.8. The state spontaneously breaks time-reversal symmetry and is sandwiched between two critical points, separating it from the broken time-reversal symmetry (BTRS) superconducting state at <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${T}_{{rm{c}}}^{U(1)}$$</jats:tex-math> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"> <mml:msubsup> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>U</mml:mi> <mml:mrow> <mml:mo>(</mml:mo> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:math> </jats:alternatives> </jats:inline-formula> and a normal-metal state at <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${T}_{{rm{c}}}^{{rm{Z2}}}$$</jats:tex-math> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"> <mml:msubsup> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>Z2</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> </jats:alternatives> </jats:inline-formula> . We report a theory of the acoustic effects spectroscopy of systems with an electron quadrupling phase based on ultrasound-velocity measurements. We show that the experimental results are consistent with BTRS superconductivity at <jats:italic>x</jats:italic> ~ 0.8, fulfilling the necessary condition for the formation of electron quadrupling in Ba <jats:sub> 1− <jats:italic>x</jats:italic> </jats:sub> K <jats:sub> <jats:italic>x</jats:italic> </jats:sub> Fe <jats:sub>2</jats:sub> As <jats:sub>2</jats:sub> . We provide the theoretical basis and the experimental strategy to study the order parameter symmetry of emerging quadrupling condensates in superconductors.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"19 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145599381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The recent discovery of altermagnets, which exhibit spin splitting without net magnetization, opens new directions for spintronics beyond the limits of ferromagnets, antiferromagnets, and spin-orbit coupled systems. We investigate spin-selective quantum transport in heterostructures composed of a normal metal and a two-dimensional d -wave altermagnet, and identify a universal mechanism for achieving perfect spin polarization. The mechanism is dictated by Fermi-surface geometry: closed surfaces in weak altermagnets yield partial and oscillatory spin filtering, whereas open surfaces in strong altermagnets intrinsically enforce fully spin-polarized conductance. Exploiting these distinct transport properties, we propose all-electrical spin-filter and spin-valve architectures, where resonant tunneling produces highly spin-polarized conductance tunable by gate voltage and interface transparency. Altermagnets with open Fermi surfaces further support gate-reversible perfect spin polarization that remains robust against interface scattering, disorder, and temperature. We also demonstrate an electrically controlled spin valve that reproduces the functionality of magnetic tunnel junctions without magnetic fields or relativistic mechanisms. d -wave altermagnets with open Fermi surfaces thus provide a new platform for low-dissipation, scalable, and magnetic-field-free spintronic devices, with potential for integration into next-generation quantum and CMOS-compatible technologies.
{"title":"All-electrically controlled spintronics in altermagnetic heterostructures","authors":"Pei-Hao Fu, Qianqian Lv, Yong Xu, Jorge Cayao, Jun-Feng Liu, Xiang-Long Yu","doi":"10.1038/s41535-025-00827-7","DOIUrl":"https://doi.org/10.1038/s41535-025-00827-7","url":null,"abstract":"The recent discovery of altermagnets, which exhibit spin splitting without net magnetization, opens new directions for spintronics beyond the limits of ferromagnets, antiferromagnets, and spin-orbit coupled systems. We investigate spin-selective quantum transport in heterostructures composed of a normal metal and a two-dimensional <jats:italic>d</jats:italic> -wave altermagnet, and identify a universal mechanism for achieving perfect spin polarization. The mechanism is dictated by Fermi-surface geometry: closed surfaces in weak altermagnets yield partial and oscillatory spin filtering, whereas open surfaces in strong altermagnets intrinsically enforce fully spin-polarized conductance. Exploiting these distinct transport properties, we propose all-electrical spin-filter and spin-valve architectures, where resonant tunneling produces highly spin-polarized conductance tunable by gate voltage and interface transparency. Altermagnets with open Fermi surfaces further support gate-reversible perfect spin polarization that remains robust against interface scattering, disorder, and temperature. We also demonstrate an electrically controlled spin valve that reproduces the functionality of magnetic tunnel junctions without magnetic fields or relativistic mechanisms. <jats:italic>d</jats:italic> -wave altermagnets with open Fermi surfaces thus provide a new platform for low-dissipation, scalable, and magnetic-field-free spintronic devices, with potential for integration into next-generation quantum and CMOS-compatible technologies.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"169 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145567695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-16DOI: 10.1038/s41535-025-00820-0
Johannes Figueiredo, Marten Richter, Mirco Troue, Jonas Kiemle, Hendrik Lambers, Torsten Stiehm, Takashi Taniguchi, Kenji Watanabe, Ursula Wurstbauer, Andreas Knorr, Alexander W. Holleitner
Heterostructures made from 2D transition-metal dichalcogenides are known as ideal platforms to explore excitonic phenomena ranging from correlated moiré excitons to degenerate interlayer exciton ensembles. So far, it is assumed that the atomic reconstruction appearing in some of the heterostructures gives rise to a dominating localization of the exciton states. We demonstrate that the center-of-mass wavefunction of the excitonic states in reconstructed MoSe2/WSe2 heterostructures can extend well beyond the moiré periodicity of the investigated heterostructures. The results are based on real-space calculations yielding a lateral potential map for interlayer excitons within the strain-relaxed heterostructures with weak random disorder, as expected for realistic samples, and the corresponding real-space center-of-mass excitonic wavefunctions. We combine the theoretical results with cryogenic photoluminescence experiments, which support the computed level structure and relaxation characteristics of the interlayer excitons.
{"title":"Laterally extended states of interlayer excitons in reconstructed MoSe2/WSe2 heterostructures","authors":"Johannes Figueiredo, Marten Richter, Mirco Troue, Jonas Kiemle, Hendrik Lambers, Torsten Stiehm, Takashi Taniguchi, Kenji Watanabe, Ursula Wurstbauer, Andreas Knorr, Alexander W. Holleitner","doi":"10.1038/s41535-025-00820-0","DOIUrl":"https://doi.org/10.1038/s41535-025-00820-0","url":null,"abstract":"<p>Heterostructures made from 2D transition-metal dichalcogenides are known as ideal platforms to explore excitonic phenomena ranging from correlated moiré excitons to degenerate interlayer exciton ensembles. So far, it is assumed that the atomic reconstruction appearing in some of the heterostructures gives rise to a dominating localization of the exciton states. We demonstrate that the center-of-mass wavefunction of the excitonic states in reconstructed MoSe<sub>2</sub>/WSe<sub>2</sub> heterostructures can extend well beyond the moiré periodicity of the investigated heterostructures. The results are based on real-space calculations yielding a lateral potential map for interlayer excitons within the strain-relaxed heterostructures with weak random disorder, as expected for realistic samples, and the corresponding real-space center-of-mass excitonic wavefunctions. We combine the theoretical results with cryogenic photoluminescence experiments, which support the computed level structure and relaxation characteristics of the interlayer excitons.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"28 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145067918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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