Symmetry and Gap Classification of Non-Symmorphic SrPtAs

Fischer, Mark H.; Goryo, Jun

doi:10.7566/jpsj.84.054705

Cited by 22 publications

(12 citation statements)

References 25 publications

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“…For the total τ z =0 interpocket pairing, the allowed symmetries of a superconducting state is further restricted by the underlying C 3 v symmetry of the lattice. In particular, the absence of an inversion centre allows the pairing wavefunction in each irreducible representation to be a mixture between parity-even and -odd functions with respect to the Γ point 45 . Specifically, s -wave mixes with f -wave and d -wave mixes with p -wave (see Fig.…”

Section: Resultsmentioning

confidence: 99%

Topological superconductivity in monolayer transition metal dichalcogenides

Hsu¹,

Vaezi²,

Fischer³

et al. 2017

Nat Commun

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171

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Theoretically, it has been known that breaking spin degeneracy and effectively realizing spinless fermions is a promising path to topological superconductors. Yet, topological superconductors are rare to date. Here we propose to realize spinless fermions by splitting the spin degeneracy in momentum space. Specifically, we identify monolayer hole-doped transition metal dichalcogenide (TMD)s as candidates for topological superconductors out of such momentum-space-split spinless fermions. Although electron-doped TMDs have recently been found superconducting, the observed superconductivity is unlikely topological because of the near spin degeneracy. Meanwhile, hole-doped TMDs with momentum-space-split spinless fermions remain unexplored. Employing a renormalization group analysis, we propose that the unusual spin-valley locking in hole-doped TMDs together with repulsive interactions selectively favours two topological superconducting states: interpocket paired state with Chern number 2 and intrapocket paired state with finite pair momentum. A confirmation of our predictions will open up possibilities for manipulating topological superconductors on the device-friendly platform of monolayer TMDs.

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Section: Resultsmentioning

confidence: 99%

Topological superconductivity in monolayer transition metal dichalcogenides

Hsu¹,

Vaezi²,

Fischer³

et al. 2017

Nat Commun

Self Cite

210

171

View full text Add to dashboard Cite

show abstract

“…We provide the reader with a simple way of testing the presented ideas by introducing a TB model on a SrPtAslike lattice adapted from Ref. [85]. This reference observed the formation of nodal surfaces in a multi-orbital d ± id SC phase [76] with an admixed p-wave component, corresponding to AZ+I class D. As illustrated in Fig.…”

Section: Example Class D Modelmentioning

confidence: 99%

“…which is I-even (more exactly, it belongs to the E 2g representation of the D 6h point group [85]). Order parameter (39a) vanishes along the vertical edges of the BZ, meaning that nodal points are formed where these edges cross the Fermi pockets.…”

Section: Example Class D Modelmentioning

confidence: 99%

Robust doubly charged nodal lines and nodal surfaces in centrosymmetric systems

2017

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Weyl points in three spatial dimensions are characterized by a Z-valued charge -the Chern number -which makes them stable against a wide range of perturbations. A set of Weyl points can mutually annihilate only if their net charge vanishes, a property we refer to as robustness. While nodal loops are usually not robust in this sense, it has recently been shown using homotopy arguments that in the centrosymmetric extension of the AI symmetry class they nevertheless develop a Z2 charge analogous to the Chern number. Nodal loops carrying a non-trivial value of this Z2 charge are robust, i.e. they can be gapped out only by a pairwise annihilation and not on their own. As this is an additional charge independent of the Berry π-phase flowing along the band degeneracy, such nodal loops are, in fact, doubly charged. In this manuscript, we generalize the homotopy discussion to the centrosymmetric extensions of all Atland-Zirnbauer classes. We develop a taylored mathematical framework dubbed the AZ+I classification and show that in three spatial dimensions such robust and multiply charged nodes appear in four of such centrosymmetric extensions, namely AZ+I classes CI and AI lead to doubly charged nodal lines, while D and BDI support doubly charged nodal surfaces. We remark that no further crystalline symmetries apart from the spatial inversion are necessary for their stability. We provide a description of the corresponding topological charges, and develop simple tight-binding models of various semimetallic and superconducting phases that exhibit these nodes. We also indicate how the concept of robust and multiply charged nodes generalizes to other spatial dimensions.arXiv:1705.07126v2 [cond-mat.mes-hall]

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“…for k on the C 3 -symmetric line. Some theoretical studies [28,55,56] have suggested such a TRS breaking chiral order parameter. Although only the PHS C is preserved in this TRS (CS) breaking superconducting state, the TRS T and the CS Γ recover by considering ∆ 0 → 0 limit.…”

Section: Classification On K-h Linementioning

confidence: 99%

Classification of topological crystalline superconducting nodes on high-symmetry lines: Point nodes, line nodes, and Bogoliubov Fermi surfaces

et al. 2019

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Recent development in exact classification of a superconducting gap has elucidated various unconventional gap structures, which have not been predicted by the classification of order parameter based on the point group. One of the important previous results is that all symmetry-protected line nodes are characterized by nontrivial topological numbers. Another intriguing discovery is the gap structures depending on the angular momentum jz of normal Bloch states on threefold and sixfold rotational-symmetric lines in the Brillouin zone. Stimulated by these findings, we classify irreducible representations of the Bogoliubov-de Gennes Hamiltonian at each k point on a highsymmetry n-fold (n = 2, 3, 4, and 6) axis for centrosymmetric and paramagnetic superconductors, by using the combination of group theory and K theory. This leads to the classification of all crystal symmetry-protected nodes (including jz-dependent nodes) on the axis that crosses a normal-state Fermi surface. As a result, it is shown that the classification by group theory completely corresponds with the topological classification. Based on the obtained results, we discuss superconducting gap structures in SrPtAs, CeCoIn5, UPt3, and UCoGe. arXiv:1811.08627v2 [cond-mat.supr-con]

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Symmetry and Gap Classification of Non-Symmorphic SrPtAs

Cited by 22 publications

References 25 publications

Topological superconductivity in monolayer transition metal dichalcogenides

Topological superconductivity in monolayer transition metal dichalcogenides

Robust doubly charged nodal lines and nodal surfaces in centrosymmetric systems

Classification of topological crystalline superconducting nodes on high-symmetry lines: Point nodes, line nodes, and Bogoliubov Fermi surfaces

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