Topological Crystalline Materials of 
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 Electrons: Antiperovskites, Dirac Points, and High Winding Topological Superconductivity

Kawakami, Takuto; Okamura, Tadao; Kobayashi, Shingo; Sato, Masatoshi

doi:10.1103/physrevx.8.041026

Cited by 58 publications

(49 citation statements)

References 76 publications

(131 reference statements)

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“…The pairing of electrons with additional internal degrees of freedom resulting, e.g., from different orbitals or basis sites, can lead to qualitatively new pairing states. Such pairing states have for example been proposed for iron-based superconductors [2][3][4][5][6][7][8][9], Cu x Bi 2 Se 3 [10,11], cubic systems such as half-Heusler compounds [12][13][14][15][16][17][18][19][20][21], UPt 3 [22,23], transition-metal dichalcogenides [24,25], and twisted bilayer graphene [26][27][28]. It has been shown that in centrosymmetric multiband superconductors that break TRS, point and line nodes are generically "inflated," by interband pairing, into Fermi surfaces of Bogoliubov quasiparticles [29,30].…”

Section: Introductionmentioning

confidence: 99%

Experimental consequences of Bogoliubov Fermi surfaces

2020

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Superconductors involving electrons with internal degrees of freedom beyond spin can have internally anisotropic pairing states that are impossible in single-band superconductors. As a case in point, in even-parity multiband superconductors that break time-reversal symmetry, nodes of the superconducting gap are generically inflated into two-dimensional Bogoliubov Fermi surfaces. The detection and characterization of these quasiparticle Fermi surfaces requires the understanding of their experimental consequences. In this paper, we derive the low-energy density of states for a broad range of possible nodal structures. Based on this, we calculate the low-temperature form of observables that are commonly employed for the characterization of nodal superconductors, i.e., the single-particle tunneling rate, the electronic specific heat and Sommerfeld coefficient, the thermal conductivity, the magnetic penetration depth, and the NMR spin-lattice relaxation rate, in the clean limit. We also address the question whether the topological invariant of the Bogoliubov Fermi surfaces is associated with topologically protected surface states, with negative results. This work is meant to serve as a guide for experimental searches for Bogoliubov Fermi surfaces in time-reversal-symmetry-breaking superconductors. arXiv:1909.10370v1 [cond-mat.supr-con]

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Section: Introductionmentioning

confidence: 99%

Experimental consequences of Bogoliubov Fermi surfaces

2020

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“…Due to the recent predictions of bulk Dirac cones [3,4] and topological nature [5] in the vicinity of the Fermi energy, antiperovskite oxides are attracting a lot of attention [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. After the initial theoretical predictions, the chemical and physical characters of antiperovskite oxides have been extensively investigated [6].…”

Section: Introductionmentioning

confidence: 99%

Negative ionic states of tin in the oxide superconductor Sr3−xSnO revealed by Mössbauer spectroscopy

et al. 2019

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We report the temperature variation of the 119 Sn-Mössbauer spectra of the antiperovskite (inverse perovskite) oxide superconductor Sr3-x SnO. Both superconductive (Sr-deficient) and nonsuperconductive (nearly stoichiometric) samples exhibit major γ-ray absorption with isomer shift similar to that of Mg2Sn. This fact shows that Sr3-x SnO contains the metallic anion Sn 4 -, which is rare especially among oxides. In both samples, we observed another γ-ray absorption with a larger isomer shift, indicating that there is another ionic state of Sn with a higher oxidation number. The temperature dependence of the absorption intensities reveals that the Sn ions exhibiting larger isomer shifts have a lower energy of the local vibration. The larger isomer shift and lower vibration energy are consistent with the values estimated from the first-principles calculations for hypothetical structures with various Sr-deficiency arrangements. Therefore, we conclude that the additional γ-ray absorptions originate from the Sn atoms neighboring the Sr deficiency. :1911.12934v1 [cond-mat.mtrl-sci] arXiv

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“…Particularly, recent developments have shown that emergent MFs appear as gapless Andreev bound states in topological superconductors (TSCs) [1][2][3][4][5][6][7][8][9][10][11][12][13][14], which provide a potential candidate for fault-tolerant qubits for topological quantum computation [15]. The increased interest in topological materials has led to a proposal of versatile three-dimensional (3D) time-reversalinvariant (TR-invariant) TSCs, such as superconducting doped topological insulators (TIs) [16][17][18][19][20][21][22][23] and Dirac semimetals [24][25][26][27][28][29], which commonly host helical MFs forming Kramers pairs on their surfaces. Emergent MFs share some properties with elementary Majorana particles [30,31].…”

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confidence: 99%

Majorana Multipole Response of Topological Superconductors

et al. 2019

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In contrast to elementary Majorana particles, emergent Majorana fermions (MFs) in condensedmatter systems may have electromagnetic multipoles. We developed a general theory of magnetic multipoles for surface helical MFs on time-reversal-invariant superconductors. The results show that the multipole response is governed by crystal symmetry, and that a one-to-one correspondence exists between the symmetry of Cooper pairs and the representation of magnetic multipoles under crystal symmetry. The latter property provides a way to identify nonconventional pairing symmetry via the magnetic response of surface MFs. We also find that most helical MFs exhibit a magnetic-dipole response, but those on superconductors with spin-3/2 electrons may display a magnetic-octupole response in leading order, which uniquely characterizes high-spin superconductors. Detection of such an octupole response provides direct evidence of high-spin superconductivity, such as in half-Heusler superconductors.

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Topological Crystalline Materials of J=3/2 Electrons: Antiperovskites, Dirac Points, and High Winding Topological Superconductivity

Cited by 58 publications

References 76 publications

Experimental consequences of Bogoliubov Fermi surfaces

Experimental consequences of Bogoliubov Fermi surfaces

Negative ionic states of tin in the oxide superconductor Sr3−xSnO revealed by Mössbauer spectroscopy

Majorana Multipole Response of Topological Superconductors

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