Pub Date : 2020-11-25DOI: 10.1103/physrevb.102.184517
A. Samoilenka, E. Babaev
We discuss the unconventional magnetic response and vortex states arising in noncentrosymmetric superconductors with chiral octahedral and tetrahedral ($O$ or $T$) symmetry. We microscopically derive Ginzburg-Landau free energy. It is shown that due to spin-orbit and Zeeman coupling magnetic response of the system can change very significantly with temperature. For sufficiently strong coupling this leads to a crossover from type-1 superconductivity at elevated temperature to vortex states at lower temperature. The external magnetic field decay in such superconductors does not have the simple exponential law. We show that in the London limit, magnetic field can be solved in terms of complex force-free fields $vec{W}$, which are defined by $nabla times vec{W} = text{const} vec{W}$. Using that we demonstrate that the magnetic field of a vortex decays in spirals. Because of such behavior of the magnetic field, the intervortex and vortex-boundary interaction becomes non-monotonic with multiple minima. This implies that vortices form bound states with other vortices, antivortices, and boundaries.
我们讨论了具有手性八面体和四面体($O$或$T$)对称的非中心对称超导体中产生的非常规磁响应和涡旋态。我们在微观上推导了金兹堡-朗道自由能。结果表明，由于自旋轨道和塞曼耦合，系统的磁响应随温度的变化非常显著。对于足够强的耦合，这将导致从高温下的1型超导到低温下的涡旋态的交叉。这种超导体的外磁场衰减不具有简单指数定律。我们表明，在伦敦极限下，磁场可以用复无力场$vec{W}$来求解，该复无力场由$nabla times vec{W} = text{const} vec{W}$定义。由此我们证明了涡旋的磁场以螺旋形式衰减。由于磁场的这种行为，涡旋间和涡旋边界相互作用变得非单调且具有多个极小值。这意味着涡旋与其他涡旋、反涡旋和边界形成束缚态。
{"title":"Spiral magnetic field and bound states of vortices in noncentrosymmetric superconductors","authors":"A. Samoilenka, E. Babaev","doi":"10.1103/physrevb.102.184517","DOIUrl":"https://doi.org/10.1103/physrevb.102.184517","url":null,"abstract":"We discuss the unconventional magnetic response and vortex states arising in noncentrosymmetric superconductors with chiral octahedral and tetrahedral ($O$ or $T$) symmetry. We microscopically derive Ginzburg-Landau free energy. It is shown that due to spin-orbit and Zeeman coupling magnetic response of the system can change very significantly with temperature. For sufficiently strong coupling this leads to a crossover from type-1 superconductivity at elevated temperature to vortex states at lower temperature. The external magnetic field decay in such superconductors does not have the simple exponential law. We show that in the London limit, magnetic field can be solved in terms of complex force-free fields $vec{W}$, which are defined by $nabla times vec{W} = text{const} vec{W}$. Using that we demonstrate that the magnetic field of a vortex decays in spirals. Because of such behavior of the magnetic field, the intervortex and vortex-boundary interaction becomes non-monotonic with multiple minima. This implies that vortices form bound states with other vortices, antivortices, and boundaries.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85093994","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}
Pub Date : 2020-11-23DOI: 10.1103/PhysRevB.103.054503
H. Miao, Y. Wang, J. Yin, J. Zhang, S. Zhang, M Zahid Hasan, R. Yang, X. -. Wang, C. Jin, T. Qian, H. Ding, H.-L. Lee, G. Kotliar
We combine transport, angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy to investigate several low energy manifestations of the Hund coupling in a canonical FeSC family Li(Fe,Co)As. We determine the doping dependence of the coherent-incoherent crossover temperature and the quasi-particle effective mass enhancement in the normal state. Our tunneling spectroscopy result in the superconducting state supports the idea that superconductivity emerging from Hund's metal state displays a universal maximal superconducting gap vs transition temperature (2$Delta_{max}/k_{B}T_{c}$) value, which is independent of doping level and $T_{c}$.
{"title":"Hund's superconductor Li(Fe,Co)As","authors":"H. Miao, Y. Wang, J. Yin, J. Zhang, S. Zhang, M Zahid Hasan, R. Yang, X. -. Wang, C. Jin, T. Qian, H. Ding, H.-L. Lee, G. Kotliar","doi":"10.1103/PhysRevB.103.054503","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.054503","url":null,"abstract":"We combine transport, angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy to investigate several low energy manifestations of the Hund coupling in a canonical FeSC family Li(Fe,Co)As. We determine the doping dependence of the coherent-incoherent crossover temperature and the quasi-particle effective mass enhancement in the normal state. Our tunneling spectroscopy result in the superconducting state supports the idea that superconductivity emerging from Hund's metal state displays a universal maximal superconducting gap vs transition temperature (2$Delta_{max}/k_{B}T_{c}$) value, which is independent of doping level and $T_{c}$.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86680442","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}
Pub Date : 2020-11-20DOI: 10.1103/PHYSREVB.103.104509
Jaechul Lee, S. Ikegaya, Y. Asano
We theoretically study the effects of spin-orbit interactions on symmetry of a Cooper pair in a spin-singlet d-wave superconductor in two-dimension. The pairing symmetry is analyzed in terms of the anomalous Green's function which is obtained by solving the Gor'kov equation analytically. A spin-orbit interaction induces a spin-triplet p-wave pairing correlation in a uniform superconductor. An odd-frequency spin-triplet s-wave pairing correlation appears at a surface of such superconductor as a result of breaking inversion symmetry locally. We also discuss a close relationship among the odd-frequency pairing correlation, chirality of surface bound states at the zero energy, and the anomalous proximity effect. The obtained results enable us to design a superconductor which causes the strong anomalous proximity effect.
{"title":"Odd-parity pairing correlations in a \u0000d\u0000-wave superconductor","authors":"Jaechul Lee, S. Ikegaya, Y. Asano","doi":"10.1103/PHYSREVB.103.104509","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.104509","url":null,"abstract":"We theoretically study the effects of spin-orbit interactions on symmetry of a Cooper pair in a spin-singlet d-wave superconductor in two-dimension. The pairing symmetry is analyzed in terms of the anomalous Green's function which is obtained by solving the Gor'kov equation analytically. A spin-orbit interaction induces a spin-triplet p-wave pairing correlation in a uniform superconductor. An odd-frequency spin-triplet s-wave pairing correlation appears at a surface of such superconductor as a result of breaking inversion symmetry locally. We also discuss a close relationship among the odd-frequency pairing correlation, chirality of surface bound states at the zero energy, and the anomalous proximity effect. The obtained results enable us to design a superconductor which causes the strong anomalous proximity effect.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82243589","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}
Pub Date : 2020-11-19DOI: 10.1103/PHYSREVAPPLIED.15.024036
E. Moncada-Villa, J. Cuevas
In recent years there has been a number of proposals of thermal devices operating in the near-field regime that make use of phase-transition materials. Here, we present a theoretical study of near-field thermal diodes and transistors that combine superconducting materials with normal (non-superconducting) metals. To be precise, we show that a system formed by two parallel plates made of Nb and Au can exhibit unprecedented rectification ratios very close to unity at temperatures around Nb superconducting critical temperature and for a wide range of gap size values within the near-field regime. Moreover, we also show that a superconducting Nb layer placed between Au plates can operate as a near-field thermal transistor where the amplification factor can be greatly tuned by varying different parameters such as the temperature and thickness of the Nb layer or the distance between the Nb layer and the Au plates. Overall, our work shows the potential of the use of superconductors for the realization of near-field thermal devices.
{"title":"Normal-Metal–Superconductor Near-Field Thermal Diodes and Transistors","authors":"E. Moncada-Villa, J. Cuevas","doi":"10.1103/PHYSREVAPPLIED.15.024036","DOIUrl":"https://doi.org/10.1103/PHYSREVAPPLIED.15.024036","url":null,"abstract":"In recent years there has been a number of proposals of thermal devices operating in the near-field regime that make use of phase-transition materials. Here, we present a theoretical study of near-field thermal diodes and transistors that combine superconducting materials with normal (non-superconducting) metals. To be precise, we show that a system formed by two parallel plates made of Nb and Au can exhibit unprecedented rectification ratios very close to unity at temperatures around Nb superconducting critical temperature and for a wide range of gap size values within the near-field regime. Moreover, we also show that a superconducting Nb layer placed between Au plates can operate as a near-field thermal transistor where the amplification factor can be greatly tuned by varying different parameters such as the temperature and thickness of the Nb layer or the distance between the Nb layer and the Au plates. Overall, our work shows the potential of the use of superconductors for the realization of near-field thermal devices.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90447823","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}
Pub Date : 2020-11-16DOI: 10.1103/PHYSREVB.103.104517
Tsz Chun Wu, H. Pal, M. Foster
We show that a Weyl superconductor can absorb light via a novel surface-to-bulk mechanism, which we dub the topological anomalous skin effect. This occurs even in the absence of disorder for a single-band superconductor, and is facilitated by the topological splitting of the Hilbert space into bulk and chiral surface Majorana states. In the clean limit, the effect manifests as a characteristic absorption peak due to surface-bulk transitions. We also consider the effects of bulk disorder, using the Keldysh response theory. For weak disorder, the bulk response is reminiscent of the Mattis-Bardeen result for $s$-wave superconductors, with strongly suppressed spectral weight below twice the pairing energy, despite the presence of gapless Weyl points. For stronger disorder, the bulk response becomes more Drude-like and the $p$-wave features disappear. We show that the surface-bulk signal survives when combined with the bulk in the presence of weak disorder. The topological anomalous skin effect can therefore serve as a fingerprint for Weyl superconductivity. We also compute the Meissner response in the slab geometry, incorporating the effect of the surface states.
{"title":"Topological anomalous skin effect in Weyl superconductors","authors":"Tsz Chun Wu, H. Pal, M. Foster","doi":"10.1103/PHYSREVB.103.104517","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.104517","url":null,"abstract":"We show that a Weyl superconductor can absorb light via a novel surface-to-bulk mechanism, which we dub the topological anomalous skin effect. This occurs even in the absence of disorder for a single-band superconductor, and is facilitated by the topological splitting of the Hilbert space into bulk and chiral surface Majorana states. In the clean limit, the effect manifests as a characteristic absorption peak due to surface-bulk transitions. We also consider the effects of bulk disorder, using the Keldysh response theory. For weak disorder, the bulk response is reminiscent of the Mattis-Bardeen result for $s$-wave superconductors, with strongly suppressed spectral weight below twice the pairing energy, despite the presence of gapless Weyl points. For stronger disorder, the bulk response becomes more Drude-like and the $p$-wave features disappear. We show that the surface-bulk signal survives when combined with the bulk in the presence of weak disorder. The topological anomalous skin effect can therefore serve as a fingerprint for Weyl superconductivity. We also compute the Meissner response in the slab geometry, incorporating the effect of the surface states.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73149033","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}
Pub Date : 2020-11-16DOI: 10.1103/PhysRevB.103.184515
Y. Takabatake, Shunpei Suzuki, Yukio Tanaka
We theoretically investigate the tunneling conductance of the $d+ip$-wave superconductor which is recently proposed to be realised at the (110) surface of a high-$T_c$ cuprate superconductor. Utilizing the quasiclassical Eilenberger theory, we obtain the self-consistent pair potentials and the differential conductance of the normal-metal/$d+ip$-wave superconductor junction. We demonstrate that the zero-bias peak of a $d$-wave superconductor is robust against the spin-triplet $p$-wave surface subdominant order even though it is fragile against the spin-singlet $s$-wave one. Comparing our numerical results and the experimental results, we conclude the spin-triplet $p$-wave surface subdominant order is feasible.
我们从理论上研究了最近提出的在高T_c铜超导体(110)表面实现的$d+ip$波超导体的隧穿电导。利用准经典的Eilenberger理论，我们得到了正常金属/$d+ $ p -波超导体结的自洽对势和微分电导。我们证明了d波超导体的零偏压峰对自旋三重态p波表面亚支配阶是鲁棒的，尽管它对自旋单线态s波表面亚支配阶是脆弱的。将数值结果与实验结果进行比较，得出自旋三重态p波表面次优序是可行的。
{"title":"Tunneling conductance of the (\u0000d+ip\u0000)-wave superconductor","authors":"Y. Takabatake, Shunpei Suzuki, Yukio Tanaka","doi":"10.1103/PhysRevB.103.184515","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.184515","url":null,"abstract":"We theoretically investigate the tunneling conductance of the $d+ip$-wave superconductor which is recently proposed to be realised at the (110) surface of a high-$T_c$ cuprate superconductor. Utilizing the quasiclassical Eilenberger theory, we obtain the self-consistent pair potentials and the differential conductance of the normal-metal/$d+ip$-wave superconductor junction. We demonstrate that the zero-bias peak of a $d$-wave superconductor is robust against the spin-triplet $p$-wave surface subdominant order even though it is fragile against the spin-singlet $s$-wave one. Comparing our numerical results and the experimental results, we conclude the spin-triplet $p$-wave surface subdominant order is feasible.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90253215","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}
Pub Date : 2020-11-13DOI: 10.1103/PHYSREVRESEARCH.3.L012021
Senna S. Luntama, P. Törmä, J. Lado
We predict that junctions between an antiferromagnetic insulator and a superconductor provide a robust platform to create a one-dimensional topological superconducting state. Its emergence does not require the presence of intrinsic spin-orbit coupling nor non-collinear magnetism, but arises solely from repulsive electronic interactions on interfacial solitonic states. We demonstrate that a topological superconducting state is generated by repulsive interactions at arbitrarily small coupling strength, and that the size of the topological gap rapidly saturates to the one of the parent trivial superconductor. Our results put forward antiferromagnetic insulators as a new platform for interaction-driven topological superconductivity.
{"title":"Interaction-induced topological superconductivity in antiferromagnet-superconductor junctions","authors":"Senna S. Luntama, P. Törmä, J. Lado","doi":"10.1103/PHYSREVRESEARCH.3.L012021","DOIUrl":"https://doi.org/10.1103/PHYSREVRESEARCH.3.L012021","url":null,"abstract":"We predict that junctions between an antiferromagnetic insulator and a superconductor provide a robust platform to create a one-dimensional topological superconducting state. Its emergence does not require the presence of intrinsic spin-orbit coupling nor non-collinear magnetism, but arises solely from repulsive electronic interactions on interfacial solitonic states. We demonstrate that a topological superconducting state is generated by repulsive interactions at arbitrarily small coupling strength, and that the size of the topological gap rapidly saturates to the one of the parent trivial superconductor. Our results put forward antiferromagnetic insulators as a new platform for interaction-driven topological superconductivity.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86909966","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}
Pub Date : 2020-11-13DOI: 10.1103/physrevb.102.195121
E. Muñoz, R. Soto-Garrido, V. Juričić
The monopole harmonic superconductor (SC), proposed in doped Weyl semimetals as a pairing between the Fermi surfaces enclosing the Weyl points, is rather unusual, as it features the monopole charge inherited from the parent metallic phase. However, this state can compete with more conventional spherical harmonic pairings, such as an $s$-wave. We here demonstrate, within the framework of the weak coupling mean-field BCS theory, that the monopole and a conventional spherical harmonic SC quite generically coexist, while the repulsion can take place when the absolute value of the monopole charge matches the angular momentum quantum number of the spherical harmonic. As we show, this feature is a direct consequence of the topological nature of the monopole SC, and we dub it emph{topological repulsion}. We illustrate the above principle with the example of the conventional $s-$ and $(p_xpm ip_y)-$wave pairings competing with the monopole SC $Y_{-1,1,0}(theta,phi)$, which coexist in a finite region of the parameter space, and repel, respectively. Furthermore, the s-wave pairing is more stable both when the chemical potentials at the nodes are unequal, and in the presence of point-like charged impurities. Since the phase transition is discontinuous, close to the phase boundary, we predict that the Majorana surface modes at the interfaces between domains featuring the monopole and the trivial phases, such as an $s-$wave, will be the experimental signature of the monopole SC.
{"title":"Monopole versus spherical harmonic superconductors: Topological repulsion, coexistence, and stability","authors":"E. Muñoz, R. Soto-Garrido, V. Juričić","doi":"10.1103/physrevb.102.195121","DOIUrl":"https://doi.org/10.1103/physrevb.102.195121","url":null,"abstract":"The monopole harmonic superconductor (SC), proposed in doped Weyl semimetals as a pairing between the Fermi surfaces enclosing the Weyl points, is rather unusual, as it features the monopole charge inherited from the parent metallic phase. However, this state can compete with more conventional spherical harmonic pairings, such as an $s$-wave. We here demonstrate, within the framework of the weak coupling mean-field BCS theory, that the monopole and a conventional spherical harmonic SC quite generically coexist, while the repulsion can take place when the absolute value of the monopole charge matches the angular momentum quantum number of the spherical harmonic. As we show, this feature is a direct consequence of the topological nature of the monopole SC, and we dub it emph{topological repulsion}. We illustrate the above principle with the example of the conventional $s-$ and $(p_xpm ip_y)-$wave pairings competing with the monopole SC $Y_{-1,1,0}(theta,phi)$, which coexist in a finite region of the parameter space, and repel, respectively. Furthermore, the s-wave pairing is more stable both when the chemical potentials at the nodes are unequal, and in the presence of point-like charged impurities. Since the phase transition is discontinuous, close to the phase boundary, we predict that the Majorana surface modes at the interfaces between domains featuring the monopole and the trivial phases, such as an $s-$wave, will be the experimental signature of the monopole SC.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80755902","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}
Pub Date : 2020-11-13DOI: 10.1103/PhysRevB.103.224504
S. Kobayashi, Y. Yamazaki, A. Yamakage, M. Sato
Emergent Majorana fermions on surfaces of time-reversal invariant topological superconductors host electromagnetic structures and realize unique electromagnetic responses. In this paper, we develop a general theory of electric and magnetic responses of the surface Majorana fermions on time-reversal invariant superconductors, on the basis of topological classification and the group theory. In particular, we provide a classification of possible electromagnetic responses of the emergent Majorana fermions arising from the interplay between topology and crystalline symmetry. It is found that the emergent Majorana fermions host magnetic structures with dipole or octupole order, and the magnetic response of a single Majorana Kramers pair directly links to Cooper pair symmetry: the magnetic structure and the Cooper pairs have a common irreducible representation under crystalline symmetry. This result provides a new perspective for the identification of unconventional Cooper pairings in topological superconductors through surface-spin-sensitive measurements. We also identify a set of crystalline symmetries without magnetic dipole response, which leads to a magnetic octupole response as the leading contribution. Such a magnetic octupole response provides a unique indication of exotic topological superconductors like topological superconductors associated with $J=3/2$ electrons or nonsymmorphic symmetry. We also clarify that multiple Kramers pairs give an electric response.
{"title":"Majorana multipole response: General theory and application to wallpaper groups","authors":"S. Kobayashi, Y. Yamazaki, A. Yamakage, M. Sato","doi":"10.1103/PhysRevB.103.224504","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.224504","url":null,"abstract":"Emergent Majorana fermions on surfaces of time-reversal invariant topological superconductors host electromagnetic structures and realize unique electromagnetic responses. In this paper, we develop a general theory of electric and magnetic responses of the surface Majorana fermions on time-reversal invariant superconductors, on the basis of topological classification and the group theory. In particular, we provide a classification of possible electromagnetic responses of the emergent Majorana fermions arising from the interplay between topology and crystalline symmetry. It is found that the emergent Majorana fermions host magnetic structures with dipole or octupole order, and the magnetic response of a single Majorana Kramers pair directly links to Cooper pair symmetry: the magnetic structure and the Cooper pairs have a common irreducible representation under crystalline symmetry. This result provides a new perspective for the identification of unconventional Cooper pairings in topological superconductors through surface-spin-sensitive measurements. We also identify a set of crystalline symmetries without magnetic dipole response, which leads to a magnetic octupole response as the leading contribution. Such a magnetic octupole response provides a unique indication of exotic topological superconductors like topological superconductors associated with $J=3/2$ electrons or nonsymmorphic symmetry. We also clarify that multiple Kramers pairs give an electric response.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87759429","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}
Pub Date : 2020-11-13DOI: 10.1103/physrevb.102.224503
Yupeng Li, Zongxiu Wu, Jingang Zhou, K. Bu, Chenchao Xu, Lei Qiao, Miaocong Li, H. Bai, Jiang Ma, Q. Tao, C. Cao, Yi Yin, Zhu-An Xu
Coexistence of topological bands and charge density wave (CDW) in topological materials has attracted immense attentions because of their fantastic properties, such as axionic-CDW, three-dimensional quantum Hall effect, etc. In this work, a nodal-line semimetal InxTaS2 characterized by CDW and superconductivity is successfully synthesized, whose structure and topological bands (two separated Wely rings) are similar to In0.58TaSe2. A 2 x 2 commensurate CDW is observed at low temperature in InxTaS2, identified by transport properties and STM measurements. Moreover, superconductivity emerges below 0.69 K, and the anisotropy ratio of upper critical field [Gamma = H||ab c2(0)=H||c c2(0)] is significantly enhanced compared to 2H-TaS2, which shares the same essential layer unit. According to the Lawrence-Doniach model, the enhanced Gamma may be explained by the reduced effective mass in kx-ky plane, where Weyl rings locate. Therefore, this type of layered topological systems may offer a platform to investigate highly anisotropic superconductivity and to understand the extremely large upper critical field in the bulk or in the two-dimensional limit.
拓扑带与电荷密度波(CDW)在拓扑材料中的共存，因其具有轴子-CDW、三维量子霍尔效应等奇异特性而受到广泛关注。本文成功合成了具有CDW和超导特性的节线半金属InxTaS2，其结构和拓扑带(两个分离的Wely环)与In0.58TaSe2相似。通过输运性质和STM测量，在InxTaS2中观察到一个2 × 2相称的CDW。此外，在0.69 K以下出现了超导性，且上临界场的各向异性比值[Gamma =H|| ab c2(0)=H||c c2(0)]与具有相同基本层单元的2H-TaS2相比显著增强。根据Lawrence-Doniach模型，伽马射线的增强可以用Weyl环所在的kx-ky平面上有效质量的减小来解释。因此，这种类型的层状拓扑系统可以为研究高各向异性超导性和理解块体或二维极限中的极大上限临界场提供平台。
{"title":"Enhanced anisotropic superconductivity in the topological nodal-line semimetal \u0000InxTaS2","authors":"Yupeng Li, Zongxiu Wu, Jingang Zhou, K. Bu, Chenchao Xu, Lei Qiao, Miaocong Li, H. Bai, Jiang Ma, Q. Tao, C. Cao, Yi Yin, Zhu-An Xu","doi":"10.1103/physrevb.102.224503","DOIUrl":"https://doi.org/10.1103/physrevb.102.224503","url":null,"abstract":"Coexistence of topological bands and charge density wave (CDW) in topological materials has attracted immense attentions because of their fantastic properties, such as axionic-CDW, three-dimensional quantum Hall effect, etc. In this work, a nodal-line semimetal InxTaS2 characterized by CDW and superconductivity is successfully synthesized, whose structure and topological bands (two separated Wely rings) are similar to In0.58TaSe2. A 2 x 2 commensurate CDW is observed at low temperature in InxTaS2, identified by transport properties and STM measurements. Moreover, superconductivity emerges below 0.69 K, and the anisotropy ratio of upper critical field [Gamma = H||ab c2(0)=H||c c2(0)] is significantly enhanced compared to 2H-TaS2, which shares the same essential layer unit. According to the Lawrence-Doniach model, the enhanced Gamma may be explained by the reduced effective mass in kx-ky plane, where Weyl rings locate. Therefore, this type of layered topological systems may offer a platform to investigate highly anisotropic superconductivity and to understand the extremely large upper critical field in the bulk or in the two-dimensional limit.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79486635","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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