Tunneling spectroscopy of few-monolayer NbSe 2 in high magnetic fields: Triplet superconductivity and Ising protection

Autor: M. Kuzmanović, T. Dvir, D. LeBoeuf, S. Ilić, M. Haim, D. Möckli, S. Kramer, M. Khodas, M. Houzet, J. S. Meyer, M. Aprili, H. Steinberg, C. H. L. Quay
Přispěvatelé: Laboratoire de Physique des Solides (LPS), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Aalto University School of Science and Technology [Aalto, Finland], The Hebrew University of Jerusalem (HUJ), Delft University of Technology (TU Delft), Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI-G ), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Centro de Fisica de Materiales (CFM), Universidad del Pais Vasco / Euskal Herriko Unibertsitatea [Espagne] (UPV/EHU)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Universidade Federal do Rio Grande do Sul [Porto Alegre] (UFRGS), Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), ANR-10-LABX-0051,LANEF,Laboratory of Alliances on Nanosciences - Energy for the Future(2010), European Project: 637928,H2020,ERC-2014-STG,TUNNEL(2015), Council for Higher Education (Israel), Agence Nationale de la Recherche (France), European Commission, European Research Council, Israel Science Foundation, Azrieli Foundation, Superconducting Qubits and Circuit QED, Hebrew University of Jerusalem, Université Grenoble Alpes, Université Paris-Saclay, Department of Applied Physics, Aalto-yliopisto, Aalto University
Jazyk: angličtina
Rok vydání: 2022
Předmět:
Zdroj: Physical Review B
Physical Review B, 2022, 106 (18), pp.184514. ⟨10.1103/PhysRevB.106.184514⟩
Physical Review B, 106(18)
ISSN: 2469-9950
2469-9969
DOI: 10.1103/PhysRevB.106.184514⟩
Popis: In conventional Bardeen-Cooper-Schrieffer superconductors, Cooper pairs of electrons of opposite spin (i.e., singlet structure) form the ground state. Equal-spin triplet pairs (ESTPs), as in superfluid 3He, are of great interest for superconducting spintronics and topological superconductivity, yet remain elusive. Recently, odd-parity ESTPs were predicted to arise in (few-)monolayer superconducting NbSe2, from the noncollinearity between the out-of-plane Ising spin-orbit field (due to the lack of inversion symmetry in monolayer NbSe2) and an applied in-plane magnetic field. These ESTPs couple to the singlet order parameter at finite field. Using van der Waals tunnel junctions, we perform spectroscopy of superconducting NbSe2 flakes, of 2–25 monolayer thickness, measuring the quasiparticle density of states (DOS) as a function of applied in-plane magnetic field up to 33 T. In flakes ≲15 monolayers thick the DOS has a single superconducting gap. In these thin samples, the magnetic field acts primarily on the spin (vs orbital) degree of freedom of the electrons, and superconductivity is further protected by the Ising field. The superconducting energy gap, extracted from our tunneling spectra, decreases as a function of the applied magnetic field. However, in bilayer NbSe2, close to the critical field (up to 30 T, much larger than the Pauli limit), superconductivity appears to be more robust than expected from Ising protection alone. Our data can be explained by the above-mentioned ESTPs.
This work was funded by a Maimonides-Israel grant from the Israeli-French High Council for Scientific and Technological Research; JCJC (SPINOES), PIRE (HYBRID), and PRC (TRIPRES) grants from the French Agence Nationale de Recherche; European Research Council Starting Grant No. ERC-2014-STG 637928 (TUNNEL); Israel Science Foundation Grants No. 861/19 and No. 2665/20, and the Laboratoire d’Excellence LANEF in Grenoble (ANR10-LABX-51-01). T.D. is grateful to the Azrieli Foundation for an Azrieli Fellowship. Part of this work has been performed at the Laboratoire National de Champs Magnétiques Intenses (LNCMI), a member of the European Magnetic Field Laboratory (EMFL).
Databáze: OpenAIRE
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