Nematic and chiral superconductivity induced by odd-parity fluctuations

Wu, Fengcheng; Martin, Ivar

doi:10.1103/physrevb.96.144504

Cited by 43 publications

(47 citation statements)

References 55 publications

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“…We interpret the surprising evolution of H c2 as due to an emergent fully-opened isotropic gap for large x. It was previously pointed out that the odd-parity superconductivity with two-component E u representation admits 40,41 . Under some circumstances, a chiral, fully-gapped, state becomes more stable as compared to a nematic state.…”

Section: Discussionmentioning

confidence: 62%

Direction and symmetry transition of the vector order parameter in topological superconductors CuxBi2Se3

et al. 2020

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Topological superconductors have attracted wide-spreading interests for the bright application perspectives to quantum computing. Cu 0.3 Bi 2 Se 3 is a rare bulk topological superconductor with an odd-parity wave function, but the details of the vector order parameter d and its pinning mechanism are still unclear. Here, we succeed in growing Cu x Bi 2 Se 3 single crystals with unprecedented high doping levels. For samples with x = 0.28, 0.36 and 0.37 with similar carrier density as evidenced by the Knight shift, the in-plane upper critical field H c2 shows a two-fold symmetry. However, the angle at which the H c2 becomes minimal is different by 90°among them, which indicates that the d-vector direction is different for each crystal likely due to a different local environment. The carrier density for x = 0.46 and 0.54 increases substantially compared to x ≤ 0.37. Surprisingly, the in-plane H c2 anisotropy disappears, indicating that the gap symmetry undergoes a transition from nematic to isotropic (possibly chiral) as carrier increases.

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Section: Discussionmentioning

confidence: 62%

Direction and symmetry transition of the vector order parameter in topological superconductors CuxBi2Se3

et al. 2020

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“…In this regard, a promising topological superconductor candidate Sr 0.1 Bi 2 Se 3 with quasi-two-dimensional structure and strong SOC has come to our attention. Sr 0.1 Bi 2 Se 3 is a member of the M x Bi 2 Se 3 (M=Cu, Sr, Nb) family, which become superconducting by doping the topological insulator Bi 2 Se 3 14–38 . Bi 2 Se 3 crystallises in a layered hexagonal structure with the space group (Fig.…”

Section: Introductionmentioning

confidence: 99%

Evidence for singular-phonon-induced nematic superconductivity in a topological superconductor candidate Sr0.1Bi2Se3

Wang

Ran

et al. 2019

Nat Commun

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Superconductivity mediated by phonons is typically conventional, exhibiting a momentum-independent s -wave pairing function, due to the isotropic interactions between electrons and phonons along different crystalline directions. Here, by performing inelastic neutron scattering measurements on a superconducting single crystal of Sr 0.1 Bi 2 Se 3 , a prime candidate for realizing topological superconductivity by doping the topological insulator Bi 2 Se 3 , we find that there exist highly anisotropic phonons, with the linewidths of the acoustic phonons increasing substantially at long wavelengths, but only for those along the [001] direction. This observation indicates a large and singular electron-phonon coupling at small momenta, which we propose to give rise to the exotic p -wave nematic superconducting pairing in the M x Bi 2 Se 3 (M = Cu, Sr, Nb) superconductor family. Therefore, we show these superconductors to be example systems where electron-phonon interaction can induce more exotic superconducting pairing than the s -wave, consistent with the topological superconductivity.

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“…However the chiral state might be more energetically favorable in the quasi-two-dimensional limit of these Dirac materials, in which the Fermi surface is cylindrical. The type of the superconducting pairing and the Majorana surface states are subjects of intense investigation and debate [10][11][12][13].For a review of the superconducting instabilities in these materials, see Ref. [14].We consider superconductivity in a Dirac metal.…”

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confidence: 99%

Antichiral and nematicity-wave superconductivity

2019

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Larkin-Ovchinnikov superconducting state has spontaneous modulation of Cooper pair density, while Fulde-Ferrell state has a spontaneous modulation in the phase of the order parameter. We report that a quasi-two-dimensional Dirac metal, under certain conditions has principally different inhomogeneous superconducting states that by contrast have spontaneous modulation in a submanifold of a multiple-symmetries-breaking order parameter. The first state we find can be viewed as a nematic superconductor where the nematicity vector spontaneously breaks rotational and translational symmetries due to spatial modulation. The other demonstrated state is a chiral superconductor with spontaneously broken time-reversal and translational symmetries. It is characterized by an order parameter, which forms a lattice pattern of alternating chiralities.For most superconductors, the ground state represents a configuration where the superconducting fields are homogeneous and can be classified according to the pairing symmetries. A generalization was theoretically proposed by Larkin and Ovchinnikov [1] and independently by Fulde and Ferrell [2]. It was demonstrated that not only U (1) symmetry can be broken in such a superconducting state but also the translational symmetry due to formation of Cooper pairs occurring with finite momentum. That state is called Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) state. In the simplest case, it can be caused by the pair-breaking effect of the Zeeman field in conventional superconductors. There are other mechanisms for the formation of inhomogeneous states in different systems such as cold atoms [3], or dense quark matter in neutron star interiors [4]. This made periodically modulated superconducting and superfluid states a subject of wide interest (for reviews see Refs. [5,6]).In this Rapid Communication we discuss a class of materials that supports inhomogeneous states which are principally different from the LOFF solutions. Namely, we find an inhomogeneous counterpart of the chiral superconducting state, where the system spontaneously forms a pattern of alternating chiralities, thereby breaking both translational and time reversal symmetries. Since the time reversal shares Z 2 symmetry with Ising magnets, we term this state as "antichiral" state in analogy to the antiferromagnetism. Another state we find is an inhomogeneous counterpart of the nematic superconducting state where the nematic vector is modulated, forming a nematicity-wave.We show that these states occur for the type of microscopic physics like that found in the recently discovered doped topological insulators [7][8][9]. Experimental studies of these materials suggest the presence of nematicity in the superconducting state with two components and odd-parity symmetric order parameter. However the chiral state might be more energetically favorable in the quasi-two-dimensional limit of these Dirac materials, in which the Fermi surface is cylindrical. The type of the superconducting pairing and the Majorana surface states are subjects of in...

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Nematic and chiral superconductivity induced by odd-parity fluctuations

Cited by 43 publications

References 55 publications

Direction and symmetry transition of the vector order parameter in topological superconductors CuxBi2Se3

Direction and symmetry transition of the vector order parameter in topological superconductors CuxBi2Se3

Evidence for singular-phonon-induced nematic superconductivity in a topological superconductor candidate Sr0.1Bi2Se3

Antichiral and nematicity-wave superconductivity

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