Daniele Guerci, Daniel Kaplan, Julian Ingham, J. H. Pixley, Andrew J. Millis
The recent observation of superconductivity in twisted bilayer WSe$_2$ raises intriguing questions concerning the origin and the properties of superconducting states realized in bands with non-trivial topological properties and repulsive electron-electron interactions. Using a continuum band structure model, we analyze a mechanism for Coulomb interaction-driven superconductivity in twisted bilayers of WSe$_2$. We discuss the symmetries and the phenomenological properties of the resulting superconducting phases and their evolution with interlayer potential difference, tunable via an out of plane electric field. The pairing strength is a non-monotonic function of interlayer potential, being larger at intermediate values due to mixing of singlet and triplet pairing. In contrast, at larger interlayer potential, the pairing tendency is suppressed due to enhanced Coulomb repulsion. The superconducting state is chiral in a large regime of parameters and undergoes a transition to a nodal nematic superconductor at a critical potential difference. The chiral state, characterized by an intervalley-symmetric superposition of triplet and singlet pairs, is classified as a topological superconductor within the Altland-Zirnbauer class C. At zero interlayer potential difference, the superconducting state is instead of class D, which hosts Majorana zero modes, making it a promising candidate for applications in quantum computation.
最近在扭曲双层 WSe$_2$ 中观察到的超导现象，提出了有关在具有非三维拓扑特性和排斥性电子-电子相互作用的带中实现的超导态的起源和性质的引人深思的问题。利用连续带结构模型，我们分析了 WSe$_2$ 扭曲双层中库仑相互作用驱动的超导机制。我们讨论了由此产生的超导相的对称性和现象学特性，以及它们随层间电位差的演变。配对强度是层间电势的非单调函数，在中间值时，由于小包和三重配对的混合，配对强度较大。相反，在层间电位较大时，由于库仑斥力增强，配对趋势受到抑制。超导态在很大的参数范围内是手性的，并在临界电位差时转变为结点向列超导体。这种手性态的特点是三重子和单重子对的间隔对称叠加，被归类为阿尔特兰-齐恩鲍尔 C 类拓扑超导体。在零层间电位差时，超导态转为 D 类，其中寄存着马约拉纳零模式，使其成为量子计算应用的理想候选者。
{"title":"Topological superconductivity from repulsive interactions in twisted WSe$_2$","authors":"Daniele Guerci, Daniel Kaplan, Julian Ingham, J. H. Pixley, Andrew J. Millis","doi":"arxiv-2408.16075","DOIUrl":"https://doi.org/arxiv-2408.16075","url":null,"abstract":"The recent observation of superconductivity in twisted bilayer WSe$_2$ raises\u0000intriguing questions concerning the origin and the properties of\u0000superconducting states realized in bands with non-trivial topological\u0000properties and repulsive electron-electron interactions. Using a continuum band\u0000structure model, we analyze a mechanism for Coulomb interaction-driven\u0000superconductivity in twisted bilayers of WSe$_2$. We discuss the symmetries and\u0000the phenomenological properties of the resulting superconducting phases and\u0000their evolution with interlayer potential difference, tunable via an out of\u0000plane electric field. The pairing strength is a non-monotonic function of\u0000interlayer potential, being larger at intermediate values due to mixing of\u0000singlet and triplet pairing. In contrast, at larger interlayer potential, the\u0000pairing tendency is suppressed due to enhanced Coulomb repulsion. The\u0000superconducting state is chiral in a large regime of parameters and undergoes a\u0000transition to a nodal nematic superconductor at a critical potential\u0000difference. The chiral state, characterized by an intervalley-symmetric\u0000superposition of triplet and singlet pairs, is classified as a topological\u0000superconductor within the Altland-Zirnbauer class C. At zero interlayer\u0000potential difference, the superconducting state is instead of class D, which\u0000hosts Majorana zero modes, making it a promising candidate for applications in\u0000quantum computation.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chao Li, Vladislav Pokorný, Martin Žonda, Jung-Ching Liu, Ping Zhou, Outhmane Chahib, Thilo Glatzel, Robert Häner, Silvio Decurtins, Shi-Xia Liu, Rémy Pawlak, Ernst Meyer
Magnetic impurities on superconductors present a viable platform for building advanced applications in quantum technologies. However, a controlled manipulation of their quantum states continues to pose a significant challenge, hindering the progress in the field. Here we show the manipulation of magnetic states in the radical molecule 4,5,9,10-tetrabromo-1,3,6,8-tetraazapyrene (TBTAP) on a Pb(111) superconducting surface using low-temperature scanning tunneling microscopy. Tunneling spectra reveal Yu-Shiba-Rusinov (YSR) states near the Fermi energy in isolated molecules. A quantum phase transition from singlet to doublet ground state is induced by changing the tip-molecule distance. Additionally, the presence of a second TBTAP molecule allows tuning of the YSR state position by altering the relative distance and can induce splitting of the YSR states for certain orientations. The construction of molecular chains up to pentamers shows periodic arrangements of charged and neutral molecules, with even-numbered chains forming a charged dimer structure at one end. Information can be encoded in these chains by switching the dimer position. These findings elucidate interactions between molecular assemblies and superconducting substrates, paving the way for advanced quantum-state engineering.
{"title":"Nanoscale Control of Quantum States in Radical Molecules on Superconducting Pb(111)","authors":"Chao Li, Vladislav Pokorný, Martin Žonda, Jung-Ching Liu, Ping Zhou, Outhmane Chahib, Thilo Glatzel, Robert Häner, Silvio Decurtins, Shi-Xia Liu, Rémy Pawlak, Ernst Meyer","doi":"arxiv-2408.05115","DOIUrl":"https://doi.org/arxiv-2408.05115","url":null,"abstract":"Magnetic impurities on superconductors present a viable platform for building\u0000advanced applications in quantum technologies. However, a controlled\u0000manipulation of their quantum states continues to pose a significant challenge,\u0000hindering the progress in the field. Here we show the manipulation of magnetic\u0000states in the radical molecule 4,5,9,10-tetrabromo-1,3,6,8-tetraazapyrene\u0000(TBTAP) on a Pb(111) superconducting surface using low-temperature scanning\u0000tunneling microscopy. Tunneling spectra reveal Yu-Shiba-Rusinov (YSR) states\u0000near the Fermi energy in isolated molecules. A quantum phase transition from\u0000singlet to doublet ground state is induced by changing the tip-molecule\u0000distance. Additionally, the presence of a second TBTAP molecule allows tuning\u0000of the YSR state position by altering the relative distance and can induce\u0000splitting of the YSR states for certain orientations. The construction of\u0000molecular chains up to pentamers shows periodic arrangements of charged and\u0000neutral molecules, with even-numbered chains forming a charged dimer structure\u0000at one end. Information can be encoded in these chains by switching the dimer\u0000position. These findings elucidate interactions between molecular assemblies\u0000and superconducting substrates, paving the way for advanced quantum-state\u0000engineering.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Božidar N. Šoškić, Jonas Bekaert, Cem Sevik, Milorad V. Milošević
Borophene stands out among elemental two-dimensional materials due to its extraordinary physical properties, including structural polymorphism, strong anisotropy, metallicity, and the potential for phonon-mediated superconductivity. However, confirming superconductivity in borophene experimentally has been evasive to date, mainly due to the detrimental effects of metallic substrates and its susceptibility to oxidation. In this study, we present an textit{ab initio} analysis of superconductivity in the experimentally synthesized hydrogenated $beta_{12}$ borophene, which has been proven to be less prone to oxidation. Our findings demonstrate that hydrogenation significantly enhances both the stability and superconducting properties of $beta_{12}$ borophene. Furthermore, we reveal that tensile strain and hole doping, achievable through various experimental methods, significantly enhance the critical temperature, reaching up to 29 K. These findings not only promote further fundamental research on superconducting borophene and its heterostructures, but also position hydrogenated borophene as a versatile platform for low-dimensional superconducting electronics.
{"title":"Enhanced superconductivity of hydrogenated $β_{12}$ borophene","authors":"Božidar N. Šoškić, Jonas Bekaert, Cem Sevik, Milorad V. Milošević","doi":"arxiv-2408.04956","DOIUrl":"https://doi.org/arxiv-2408.04956","url":null,"abstract":"Borophene stands out among elemental two-dimensional materials due to its\u0000extraordinary physical properties, including structural polymorphism, strong\u0000anisotropy, metallicity, and the potential for phonon-mediated\u0000superconductivity. However, confirming superconductivity in borophene\u0000experimentally has been evasive to date, mainly due to the detrimental effects\u0000of metallic substrates and its susceptibility to oxidation. In this study, we\u0000present an textit{ab initio} analysis of superconductivity in the\u0000experimentally synthesized hydrogenated $beta_{12}$ borophene, which has been\u0000proven to be less prone to oxidation. Our findings demonstrate that\u0000hydrogenation significantly enhances both the stability and superconducting\u0000properties of $beta_{12}$ borophene. Furthermore, we reveal that tensile\u0000strain and hole doping, achievable through various experimental methods,\u0000significantly enhance the critical temperature, reaching up to 29 K. These\u0000findings not only promote further fundamental research on superconducting\u0000borophene and its heterostructures, but also position hydrogenated borophene as\u0000a versatile platform for low-dimensional superconducting electronics.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141968660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We successfully synthesized samples of La$_{3}$Ni$_{2}$O$_{7+delta}$ ($delta = -0.50$, $-0.16$, $0.00$, $+0.01$, and $+0.12$) and measured the resistance under extremely high pressures using a diamond anvil cell to establish the electronic phase diagram. A Mott insulating state appears at $delta = -0.50$, where all Ni ions are divalent. With increasing oxygen content, superconductivity appears at $delta = 0.00$ and higher, above approximately 25 GPa, passing through Anderson localization at $delta = -0.16$. The superconducting transition temperature $T_{mathrm{c}}$ decreases with increasing pressures for both $delta = 0.00$ and $+0.12$, with the pressure dependence of $T_{mathrm{c}}$ being much stronger in the latter than in the former.
{"title":"Phase diagram of pressure-induced high temperature superconductor La$_{3}$Ni$_{2}$O$_{7+δ}$","authors":"Yuta Ueki, Hiroya Sakurai, Hibiki Nagata, Kazuki Yamane, Ryo Matsumoto, Kensei Terashima, Keisuke Hirose, Hiroto Ohta, Masaki Kato, Yoshihiko Takano","doi":"arxiv-2408.04970","DOIUrl":"https://doi.org/arxiv-2408.04970","url":null,"abstract":"We successfully synthesized samples of La$_{3}$Ni$_{2}$O$_{7+delta}$\u0000($delta = -0.50$, $-0.16$, $0.00$, $+0.01$, and $+0.12$) and measured the\u0000resistance under extremely high pressures using a diamond anvil cell to\u0000establish the electronic phase diagram. A Mott insulating state appears at\u0000$delta = -0.50$, where all Ni ions are divalent. With increasing oxygen\u0000content, superconductivity appears at $delta = 0.00$ and higher, above\u0000approximately 25 GPa, passing through Anderson localization at $delta =\u0000-0.16$. The superconducting transition temperature $T_{mathrm{c}}$ decreases\u0000with increasing pressures for both $delta = 0.00$ and $+0.12$, with the\u0000pressure dependence of $T_{mathrm{c}}$ being much stronger in the latter than\u0000in the former.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":"131 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We measured the temporal voltage response of NbTi superconducting filaments with varied nanoscale thicknesses to step current pulses that induce non-equilibrium superconducting states governed by a hot-spot mechanism. Such detected voltage emerges after a delay time td, which is intimately connected to the gap relaxation and heat escape times. By employing time-dependent Ginzburg-Landau theory to link the delay time to the applied current, we determined that the gap relaxation time depends linearly on film thickness, aligning with the acoustic mismatch theory for phonon transmission at the superconductor-substrate interface. We thereby find a gap relaxation time of 104 ps per nm of thickness for NbTi films on polished sapphire. We further show that interfacial interaction with the substrate significantly impacts the gap relaxation time, with observed values of 9 ns on SiOx, 6.8 ns on fused silica, and 5.2 ns on sapphire for a 50 nm thick NbTi strip at T = 5.75 K. These insights are valuable for optimizing superconducting sensing technologies, particularly the single-photon detectors that operate in the transient regime of nanothin superconducting bridges and filaments
{"title":"Characteristic times for gap relaxation and heat escape in nanothin NbTi superconducting filaments: thickness dependence and effect of substrate","authors":"K. Harrabi, A. Mekki, M. V. Milosevic","doi":"arxiv-2408.04516","DOIUrl":"https://doi.org/arxiv-2408.04516","url":null,"abstract":"We measured the temporal voltage response of NbTi superconducting filaments\u0000with varied nanoscale thicknesses to step current pulses that induce\u0000non-equilibrium superconducting states governed by a hot-spot mechanism. Such\u0000detected voltage emerges after a delay time td, which is intimately connected\u0000to the gap relaxation and heat escape times. By employing time-dependent\u0000Ginzburg-Landau theory to link the delay time to the applied current, we\u0000determined that the gap relaxation time depends linearly on film thickness,\u0000aligning with the acoustic mismatch theory for phonon transmission at the\u0000superconductor-substrate interface. We thereby find a gap relaxation time of\u0000104 ps per nm of thickness for NbTi films on polished sapphire. We further show\u0000that interfacial interaction with the substrate significantly impacts the gap\u0000relaxation time, with observed values of 9 ns on SiOx, 6.8 ns on fused silica,\u0000and 5.2 ns on sapphire for a 50 nm thick NbTi strip at T = 5.75 K. These\u0000insights are valuable for optimizing superconducting sensing technologies,\u0000particularly the single-photon detectors that operate in the transient regime\u0000of nanothin superconducting bridges and filaments","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaobo He, Ying Li, Yongheng Ge, Hai Zeng, Shi-Jie Song, Shuo Zou, Zhuo Wang, Yuke Li, Wenxin Ding, Jianhui Dai, Guang-Han Cao, Xiao-Xiao Zhang, Gang Xu, Yongkang Luo
It is generally believed that electronic correlation, geometric frustration, and topology, textit{individually}, can facilitate the emergence of various intriguing properties that have attracted a broad audience for both fundamental research and potential applications. Here, we report a systematic investigation on a quasi-kagome Kondo Weyl semimetal candidate Ce$_3$TiSb$_5$. A series of unconventional Hall effects are observed. In the paramagnetic phase, signature of dynamic $c$-$f$ hybridization is revealed by a reduction of anomalous Hall effect and is connected to frustration-promoted incoherent Kondo scattering. A large topological Hall effect exceeding 0.2 $muOmega$ cm is found at low temperatures, which should be ascribed to the noncolinear magnetic structures of the frustrated quasi-kagome lattice. In addition, a peculiar loop-shaped Hall effect with switching chirality is also seen, which is inferred to be associated with magnetic domain walls that pin history-dependent spin chirality and / or Fermi-arc surface states projected from the in-gap Weyl nodes. These exotic results place Ce$_3$TiSb$_5$ in a regime of highly-frustrated antiferromagnetic dense Kondo lattice with a nontrivial topology on an ``extended" global phase diagram, and highlight the interplay among electronic correlation, geometric frustration and topology.
{"title":"Unconventional Hall effects in a quasi-kagome Kondo Weyl semimetal candidate Ce$_3$TiSb$_5$","authors":"Xiaobo He, Ying Li, Yongheng Ge, Hai Zeng, Shi-Jie Song, Shuo Zou, Zhuo Wang, Yuke Li, Wenxin Ding, Jianhui Dai, Guang-Han Cao, Xiao-Xiao Zhang, Gang Xu, Yongkang Luo","doi":"arxiv-2408.04438","DOIUrl":"https://doi.org/arxiv-2408.04438","url":null,"abstract":"It is generally believed that electronic correlation, geometric frustration,\u0000and topology, textit{individually}, can facilitate the emergence of various\u0000intriguing properties that have attracted a broad audience for both fundamental\u0000research and potential applications. Here, we report a systematic investigation\u0000on a quasi-kagome Kondo Weyl semimetal candidate Ce$_3$TiSb$_5$. A series of\u0000unconventional Hall effects are observed. In the paramagnetic phase, signature\u0000of dynamic $c$-$f$ hybridization is revealed by a reduction of anomalous Hall\u0000effect and is connected to frustration-promoted incoherent Kondo scattering. A\u0000large topological Hall effect exceeding 0.2 $muOmega$ cm is found at low\u0000temperatures, which should be ascribed to the noncolinear magnetic structures\u0000of the frustrated quasi-kagome lattice. In addition, a peculiar loop-shaped\u0000Hall effect with switching chirality is also seen, which is inferred to be\u0000associated with magnetic domain walls that pin history-dependent spin chirality\u0000and / or Fermi-arc surface states projected from the in-gap Weyl nodes. These\u0000exotic results place Ce$_3$TiSb$_5$ in a regime of highly-frustrated\u0000antiferromagnetic dense Kondo lattice with a nontrivial topology on an\u0000``extended\" global phase diagram, and highlight the interplay among electronic\u0000correlation, geometric frustration and topology.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":"97 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
These lectures present the Fermi-liquid theory of superconductivity, which is applicable to a broad range of systems that are candidates for non-s wave pairing, {it e.g.} the heavy fermions, organic metals and the CuO superconductors. Ginzburg-Landau (GL) theory provides an important link between experimental properties of non-s wave superconductors and the more general Fermi-liquid theory. The multiple superconducting phases of UPt$_3$ provide an ideal example of the role that is played by the GL theory for non-s wave superconductors. The difference between non-s wave superconductivity and conventional anisotropic superconductivity is illustrated here by the unique effects that impurities are predicted to have on the properties of non-s wave superconductors.
{"title":"Fermi-Liquid Theory of Non-S-Wave Superconductivity","authors":"P. Muzikar, D. Rainer, J. A. Sauls","doi":"arxiv-2408.04151","DOIUrl":"https://doi.org/arxiv-2408.04151","url":null,"abstract":"These lectures present the Fermi-liquid theory of superconductivity, which is\u0000applicable to a broad range of systems that are candidates for non-s wave\u0000pairing, {it e.g.} the heavy fermions, organic metals and the CuO\u0000superconductors. Ginzburg-Landau (GL) theory provides an important link between\u0000experimental properties of non-s wave superconductors and the more general\u0000Fermi-liquid theory. The multiple superconducting phases of UPt$_3$ provide an\u0000ideal example of the role that is played by the GL theory for non-s wave\u0000superconductors. The difference between non-s wave superconductivity and\u0000conventional anisotropic superconductivity is illustrated here by the unique\u0000effects that impurities are predicted to have on the properties of non-s wave\u0000superconductors.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We propose an alternative experimental protocol for the detection of doped Chern insulators and chiral superconductors. Our approach relies on coupling the target chiral system to adatom spins. Due to the substrate chirality, the adatom spins are expected to order in a noncoplanar configuration with a nonzero spin chirality. Here, we obtain concrete results for chiral substrates which are invariant under arbitrary spin rotations, and are coupled to three adatoms carrying classical moments. By exploring all the accessible magnetic ground states, we identify the regimes in which nonzero spin chirality is induced on the adatom complex. We apply our method to valley-polarized bilayer graphene and $d+id$ superconductors, and find qualitatively different ground state diagrams. Our analysis shows that the adatom spin chirality fully encodes the properties of the substrate chirality.
{"title":"Imprinting Ground State Chirality on Adatom Spins","authors":"Yun-Peng Huang, Panagiotis Kotetes","doi":"arxiv-2408.04578","DOIUrl":"https://doi.org/arxiv-2408.04578","url":null,"abstract":"We propose an alternative experimental protocol for the detection of doped\u0000Chern insulators and chiral superconductors. Our approach relies on coupling\u0000the target chiral system to adatom spins. Due to the substrate chirality, the\u0000adatom spins are expected to order in a noncoplanar configuration with a\u0000nonzero spin chirality. Here, we obtain concrete results for chiral substrates\u0000which are invariant under arbitrary spin rotations, and are coupled to three\u0000adatoms carrying classical moments. By exploring all the accessible magnetic\u0000ground states, we identify the regimes in which nonzero spin chirality is\u0000induced on the adatom complex. We apply our method to valley-polarized bilayer\u0000graphene and $d+id$ superconductors, and find qualitatively different ground\u0000state diagrams. Our analysis shows that the adatom spin chirality fully encodes\u0000the properties of the substrate chirality.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rich spontaneous symmetry-breaking phenomena with nontrivial quantum geometric properties in metals represent central issues in condensed matter physics. The emergence of chiral loop-current order, accompanied by time-reversal symmetry (TRS) breaking in various kagome metals, has garnered significant attention as a novel quantum topological state. Particularly noteworthy is the giant electrical magnetochiral anisotropy (eMChA) in CsV3Sb5 [Guo et al, Nature 611, 461 (2022)], which provides compelling evidence of TRS and inversion-symmetry breaking. However, the underlying essence of this observation has remained obscured due to the lack of theoretical understanding. Here, we identify that the chiral loop-current induces substantial and switchable eMChA in kagome metals by taking account of the experimentally observed stripe charge-density-wave. The obtained eMChA coefficient is $gamma_{eM}propto M_{orb} tau$, where $M_{orb}$ is the loop-current-induced orbital magnetization and $tau$ is the lifetime of conduction electrons. Importantly, giant eMChA arises from the quantum metric (QM), which defines essential quantum phases of matter and their unique functionalities, including nonlinear effects. This effect is resonantly amplified in the loop-current phase, and the derived eMChA is switched by minute magnetic fields. This research elucidates the fundamental symmetry breaking in kagome metals and also sets the stage for investigating the QM-induced phenomena arising from electronic correlations.
{"title":"Quantum-metric-induced giant and reversible nonreciprocal transport phenomena in chiral loop-current phases of kagome metals","authors":"Rina Tazai, Youichi Yamakawa, Takahiro Morimoto, Hiroshi Kontani","doi":"arxiv-2408.04233","DOIUrl":"https://doi.org/arxiv-2408.04233","url":null,"abstract":"Rich spontaneous symmetry-breaking phenomena with nontrivial quantum\u0000geometric properties in metals represent central issues in condensed matter\u0000physics. The emergence of chiral loop-current order, accompanied by\u0000time-reversal symmetry (TRS) breaking in various kagome metals, has garnered\u0000significant attention as a novel quantum topological state. Particularly\u0000noteworthy is the giant electrical magnetochiral anisotropy (eMChA) in CsV3Sb5\u0000[Guo et al, Nature 611, 461 (2022)], which provides compelling evidence of TRS\u0000and inversion-symmetry breaking. However, the underlying essence of this\u0000observation has remained obscured due to the lack of theoretical understanding.\u0000Here, we identify that the chiral loop-current induces substantial and\u0000switchable eMChA in kagome metals by taking account of the experimentally\u0000observed stripe charge-density-wave. The obtained eMChA coefficient is\u0000$gamma_{eM}propto M_{orb} tau$, where $M_{orb}$ is the loop-current-induced\u0000orbital magnetization and $tau$ is the lifetime of conduction electrons.\u0000Importantly, giant eMChA arises from the quantum metric (QM), which defines\u0000essential quantum phases of matter and their unique functionalities, including\u0000nonlinear effects. This effect is resonantly amplified in the loop-current\u0000phase, and the derived eMChA is switched by minute magnetic fields. This\u0000research elucidates the fundamental symmetry breaking in kagome metals and also\u0000sets the stage for investigating the QM-induced phenomena arising from\u0000electronic correlations.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":"97 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xun Cai, Zhaoyu Han, Zi-Xiang Li, Steven A. Kivelson, Hong Yao
A quantum spin liquid (QSL) is an exotic insulating phase with emergent gauge fields and fractionalized excitations. However, the unambiguous demonstration of the existence of a QSL in a "non-engineered" microscopic model (or in any material) remains challenging. Here, using numerically-exact sign-problem-free quantum Monte Carlo simulations, we show that a QSL arises in a non-engineered electron-phonon model. Specifically, we investigate the ground-state phase diagram of the bond Su-Schrieffer-Heeger (SSH) model on a 2D triangular lattice at half filling (one electron per site) which we show includes a QSL phase which is fully gapped, exhibits no symmetry-breaking order, and supports deconfined fractionalized holon excitations. This suggests new routes for finding QSLs in realistic materials and high-$T_c$ superconductivity by lightly doping them.
{"title":"Quantum spin liquid from electron-phonon coupling","authors":"Xun Cai, Zhaoyu Han, Zi-Xiang Li, Steven A. Kivelson, Hong Yao","doi":"arxiv-2408.04002","DOIUrl":"https://doi.org/arxiv-2408.04002","url":null,"abstract":"A quantum spin liquid (QSL) is an exotic insulating phase with emergent gauge\u0000fields and fractionalized excitations. However, the unambiguous demonstration\u0000of the existence of a QSL in a \"non-engineered\" microscopic model (or in any\u0000material) remains challenging. Here, using numerically-exact sign-problem-free\u0000quantum Monte Carlo simulations, we show that a QSL arises in a non-engineered\u0000electron-phonon model. Specifically, we investigate the ground-state phase\u0000diagram of the bond Su-Schrieffer-Heeger (SSH) model on a 2D triangular lattice\u0000at half filling (one electron per site) which we show includes a QSL phase\u0000which is fully gapped, exhibits no symmetry-breaking order, and supports\u0000deconfined fractionalized holon excitations. This suggests new routes for\u0000finding QSLs in realistic materials and high-$T_c$ superconductivity by lightly\u0000doping them.","PeriodicalId":501069,"journal":{"name":"arXiv - PHYS - Superconductivity","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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