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Unusual 2D superconductivity and topological signatures in the Weyl and nodal line semimetal trigonal-PtBi2

Vendredi 1er décembre 2023 11:00 - Duree : 1 heure
Lieu : Salle René Pauthenet (J229, bâtiment J), LNCMI, 25 avenue des Martyrs, 38042 Grenoble

Orateur : Arthur VEYRAT (Laboratoire de physique des solides, Equipe MESO, Orsay, France)

Résumé :

Recently, topological phases of matter have attracted considerable attention due to their unique and robust properties. In particular, the possibility of finding or inducing superconductivity in a topological phase (known as topological superconductivity) has been an active area of research in recent years, for instance in quantum engineering where such a phase would be useful for quantum computing.

In this seminar, I will present a charge transport study of nanostructures of trigonal-PtBi2, a noncentrosymmetric crystal with very strong spin-orbit coupling. In recent works (1, 2), we evidenced the superconducting properties of this material and we predict it to be a Weyl- and nodal-linesemimetal. I will focus on two main results : the discovery of 2-dimensional superconductivity at sub-kelvin temperatures, and the discovery of an anomalous planar Hall effect (APHE) in the normal phase, robust up to room temperature.

While superconductivity has already been reported under pressure in t-PtBi2 above 2K (3, 4), we found that single crystals of t-PtBi2 also display superconductivity at ambient pressure, with a critical temperature Tc ∼ 600mK (1). When thinning down the crystals with mechanical exfoliation, the superconductivity becomes two-dimensional below t ∼ 70nm. Remarkably, even at such large thicknesses, nanostructures show clear Berezinskii–Kosterlitz–Thouless (BKT) transitions, a usually very fragile transition only evidenced yet in nearly-atomically thin superconducting films. This unusual feature might be related to the recent discovery in ARPES that the superconductivity occurs on the Fermi arcs, the topological surface states of Weyl semimetals.

At higher temperature (in the normal state), we discovered a large planar Hall effect – the appearance under an external in-plane magnetic field of a transverse voltage dependent on the relative orientations of the electric (current) and magnetic fields – which is a signature of Weyl physics in non-magnetic materials (5, 6). Additionally, we characterized an anomalous planar Hall response (7), which we attribute to a mechanism where topological nodal-lines – 1d band touchings in k-space, which we predict in t-PtBi2 – get converted into Weyl nodes under even infinitesimal magnetic fields. Both effects, which are signatures of topological phases, are robust up to room temperature (2).

References

1. A. Veyrat et al., Nano Letters, ISSN : 1530-6984 (Jan. 2023).

2. Arthur Veyrat et al., Just submitted to arXiv (2023).

3. J. Wang et al., Physical Review B 103, 1–6, ISSN : 24699969 (2021).

4. D. L. Bashlakov et al., Low Temperature Physics 48, 747–754, ISSN : 1063-777X, 1090-6517, arXiv : 2205.06610 (Oct. 2022).

5. A. A. Burkov, Physical Review B 96, 041110, ISSN : 2469-9950 (July 2017).

6. S. Nandy, G. Sharma, A. Taraphder, S. Tewari, Physical Review Letters 119, 1–6, ISSN:10797114 (2017).

7. R. Battilomo, N. Scopigno, C. Ortix, Physical Review Research 3, 1–6, ISSN : 2643-1564 (2021).

Contact : benjamin.piot@lncmi.cnrs.fr

Discipline évènement : (Physique)
Entité organisatrice : (LNCMI)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire LNCMI)
Site de l'évènement : Polygone scientifique

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