Two-dimensional superconductivity and magnetotransport from topological surface states in AuSn4 semimetal

Dong Shen,Chia Nung Kuo,Li Min Wang,Chin Shan Lue,Tien Wei Yang,I Nan Chen

doi:10.1038/s43246-020-00060-8

Dong Shen, Chia Nung Kuo + Show 4 more

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https://doi.org/10.1038/s43246-020-00060-8

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Abstract

Topological materials such as Dirac or Weyl semimetals are new states of matter characterized by symmetry-protected surface states responsible for exotic low-temperature magnetotransport properties. Here, transport measurements on AuSn4 single crystals, a topological nodal-line semimetal candidate, reveal the presence of two-dimensional superconductivity with a transition temperature Tc ~ 2.40 K. The two-dimensional nature of superconductivity is verified by a Berezinsky–Kosterlitz–Thouless transition, Bose-metal phase, and vortex dynamics interpreted in terms of thermally-assisted flux motion in two dimensions. The normal-state magnetoconductivity at low temperatures is found to be well described by the weak-antilocalization transport formula, which has been commonly observed in topological materials, strongly supporting the scenario that normal-state magnetotransport in AuSn4 is dominated by the surface electrons of topological Dirac-cone states. The entire results are summarized in a phase diagram in the temperature–magnetic field plane, which displays different regimes of transport. The combination of two-dimensional superconductivity and surface-driven magnetotransport suggests the topological nature of superconductivity in AuSn4.

Highlights

Topological materials such as Dirac or Weyl semimetals are new states of matter characterized by symmetry-protected surface states responsible for exotic low-temperature magnetotransport properties
Another novel state of quantum matter, the topological material, has become an important topic in condensed matter physics[10], in which the robust topological surface states are topologically protected against time reversal-invariant perturbations
The 2D superconductivity let us consider the emergence of the Bose-metal phase recently identified in 1T-MoS2 and NbSe2

Summary

Introduction

Topological materials such as Dirac or Weyl semimetals are new states of matter characterized by symmetry-protected surface states responsible for exotic low-temperature magnetotransport properties. Transport measurements on AuSn4 single crystals, a topological nodal-line semimetal candidate, reveal the presence of two-dimensional superconductivity with a transition temperature Tc ~ 2.40 K. Motivated by the prospect of creating Majorana fermions, which have potential applications in quantum computations[15], several attempts have been made to induce superconductivity on the surfaces of topological materials using bulk superconductors[17,18] or interface superconductivity induced by the superconducting proximity effect[19] He et al.[20,21] have reported transport measurements on a Bi2Te3/FeTe heterostructure with both nonsuperconducting materials, which reveal superconductivity at the interface and show the two-dimensional nature of the observed superconductivity with the highest transition temperature around 12 K. In contrast to the recently discovered 2D superconductors, which were fabricated in the shape of micrometer-size flakes with a few-layer thickness, the millimeter-size bulk AuSn4 single crystals peculiarly exhibit 2D superconductivity, and display large normalstate magnetoresistance accompanied by high carrier mobility, revealing the advantages of AuSn4 as the key to understanding topological 2D superconductivity

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