Topological Superconductivity in an s-wave Superconductor and Its Implication to Iron-based Superconductors

Qin, Shengshan; Fang, Chen; Zhang, Fu-Chun; Hu, Jiangping

doi:10.48550/arxiv.2106.04200

Cited by 3 publications

(3 citation statements)

References 92 publications

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“…This inspiring concept of TQC has motivated an intensive experimental search for Majorana zero modes [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], the simplest and most feasible building block for TQCs. While a "smoking gun" for Majorana modes is still lacking, the recent advent of topological iron-based superconductors [23][24][25][26][27][28][29][30][31][32][33][34] (tFeSCs) sheds light on resolving this long-sought Majorana mystery [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49]. Remarkably, the normal-state band structure of tFeSCs naturally contains two crucial ingredients: (i) a topological insulator (TI) part that provides helical Dirac surface state [50][51]…”

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confidence: 99%

Competing Vortex Topologies in Iron-based Superconductors

Hu¹,

Wu²,

Liu³

et al. 2021

Preprint

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In this work, we establish a new theoretical paradigm for vortex Majorana physics in the recently discovered topological iron-based superconductors (tFeSCs). While tFeSCs are widely accepted as an exemplar of topological insulators (TIs) with intrinsic superconductivity, our theory implies that such common belief could be oversimplified. Our main finding is that the normal-state bulk Dirac nodes, usually ignored in TI-based vortex Majorana theories for tFeSCs, will play a key role of determining the vortex state topology. In particular, the interplay between TI and Dirac nodal bands will lead to multiple competing topological phases for a superconducting vortex line in tFeSCs, including an unprecedented hybrid topological vortex state that carries both Majorana bound states and a gapless dispersion. Remarkably, this exotic hybrid vortex phase generally exists in the vortex phase diagram for our minimal model for tFeSCs and is directly relevant to tFeSC candidates such as LiFeAs. In the presence of lattice symmetry breaking, the hybrid vortex gets topologically trivialized and becomes Majorana-free, which naturally explains the puzzle of ubiquitous trivial vortices observed in LiFeAs. Origin of Majorana signal in other tFeSC candidates such as FeTexSe1−x and CaKFe4As4 are also interpreted within our theory framework. Our theory sheds new light on theoretically understanding and experimentally engineering Majorana physics in high-temperature iron-based systems.

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confidence: 99%

Competing Vortex Topologies in Iron-based Superconductors

Hu¹,

Wu²,

Liu³

et al. 2021

Preprint

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“…Employing physically realistic parameters, we find three adjacent superconducting phases -one first-order topological p + ip intervalley, and two higher-order topological: s τ intervalley, and p + iτ p intravalley -with spin-orbit coupling entangling the valley and spin polarisation of the Cooper pairs. The s τ state is similar to the s ± state discussed in the context of iron-based superconductors, which consists of s-wave pairing but with a gap that has opposite signs at the hole and electron pockets [94][95][96][97][98][99]; here, the valley structure imposes that s-wave state changes sign under exchange of the valleys.…”

mentioning

confidence: 71%

Intrinsic first and higher-order topological superconductivity in a doped topological insulator

Scammell,

Ingham,

Geier

et al. 2021

Preprint

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We explore higher order topological superconductivity in an artificial Dirac material with intrinsic spin-orbit coupling, which is a doped Z2 topological insulator in the normal state. A mechanism for superconductivity due to repulsive interactions -pseudospin pairing -has recently been shown to naturally result in higher-order topology in Dirac systems past a minimum chemical potential [1].Here we apply this theory through microscopic modeling of a superlattice potential imposed on an inversion symmetric hole-doped semiconductor heterostructure, known as hole-based semiconductor artificial graphene, and extend previous work to include the effects of spin-orbit coupling. We find that spin-orbit coupling enhances interaction effects, providing an experimental handle to increase the efficiency of the superconducting mechanism. We show that the phase diagram of these systems, as a function of chemical potential and interaction strength, contains three superconducting states -a first-order topological p + ip state, a second-order topological spatially modulated p + iτ p state, and a second-order topological extended s-wave state, sτ . We calculate the symmetry-based indicators for the p+iτ p and sτ states, which prove these states possess second-order topology. Exact diagonalisation results are presented which illustrate the interplay between the boundary physics and spin orbit interaction. We argue that this class of systems offer an experimental platform to engineer and explore first and higher-order topological superconducting states.

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“…Therefore, the SC has |C M | = 2 on the ΓL 1 L 3 plane. For a SC with an even mirror Chern number, it must be a second-order TSC protected by the mirror symmetry 99,105 . Correspondingly, two Majorana cones are expected on the surfaces where M a is preserved, such as the (001) plane, along Γ X as shown in Fig.…”

Section: T2umentioning

confidence: 99%

Theory of Topological Superconductivity in Doped IV-VI Semiconductors

Li,

Qin,

Ren

et al. 2021

Preprint

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We theoretically study potential unconventional superconductivity in doped AB-type IV-VI semiconductors, based on a minimal effective model with interaction up to the next-nearest neighbors. According to the experimental implications, we focus on the spin-triplet channels and obtain the superconducting phase diagram with respect to the anisotropy of the Fermi surfaces and the interaction strength. All the states in the phase diagram are time reversal invariant and are topologically nontrivial. Specifically, in the phase diagram there appear a mirror symmetry protected topological Dirac superconductor phase, a mirror symmetry protected second-order topological superconductor phase, and a full-gap topological superconductor phase with winding number 4. The point group symmetry breaking of each superconducting ground state is also discussed.

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Topological Superconductivity in an s-wave Superconductor and Its Implication to Iron-based Superconductors

Cited by 3 publications

References 92 publications

Competing Vortex Topologies in Iron-based Superconductors

Competing Vortex Topologies in Iron-based Superconductors

Intrinsic first and higher-order topological superconductivity in a doped topological insulator

Theory of Topological Superconductivity in Doped IV-VI Semiconductors

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