Berezinskii-Kosterlitz-Thouless Transition in the Type-I Weyl Semimetal PtBi<sub>2</sub>.

Veyrat, Arthur; Labracherie, Valentin; Bashlakov, Dima L; Caglieris, Federico; Facio, Jorge I; Shipunov, Grigory; Charvin, Titouan; Acharya, Rohith et al. · Nano Lett · 2023

basic_science · Level V

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Abstract

Symmetry breaking in topological matter has become in recent years a key concept in condensed matter physics to unveil novel electronic states. In this work, we predict that broken inversion symmetry and strong spin-orbit coupling in trigonal PtBi<sub>2</sub> lead to a type-I Weyl semimetal band structure. Transport measurements show an unusually robust low dimensional superconductivity in thin exfoliated flakes up to 126 nm in thickness (with <i>T</i><sub>c</sub> ∼ 275-400 mK), which constitutes the first report and study of unambiguous superconductivity in a type-I Weyl semimetal. Remarkably, a Berezinskii-Kosterlitz-Thouless transition with <i>T</i><sub>BKT</sub> ∼ 310 mK is revealed in up to 60 nm thick flakes, which is nearly an order of magnitude thicker than the rare examples of two-dimensional superconductors exhibiting such a transition. This makes PtBi<sub>2</sub> an ideal platform to study low dimensional and unconventional superconductivity in topological semimetals.