Review Article

Highly crystalline 2D superconductors

Published online:

Abstract

Recent advances in materials fabrication have enabled the manufacturing of ordered 2D electron systems, such as heterogeneous interfaces, atomic layers grown by molecular beam epitaxy, exfoliated thin flakes and field-effect devices. These 2D electron systems are highly crystalline, and some of them, despite their single-layer thickness, exhibit a sheet resistance more than an order of magnitude lower than that of conventional amorphous or granular thin films. In this Review, we explore recent developments in the field of highly crystalline 2D superconductors and highlight the unprecedented physical properties of these systems. In particular, we explore the quantum metallic state (or possible metallic ground state), the quantum Griffiths phase observed in out-of-plane magnetic fields and the superconducting state maintained in anomalously large in-plane magnetic fields. These phenomena are examined in the context of weakened disorder and/or broken spatial inversion symmetry. We conclude with a discussion of how these unconventional properties make highly crystalline 2D systems promising platforms for the exploration of new quantum physics and high-temperature superconductors.

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Author information

Affiliations

  1. Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113–8656, Japan.

    • Yu Saito
    •  & Yoshihiro Iwasa
  2. Institute for Materials Research, Tohoku University, Sendai 980–8577, Japan.

    • Tsutomu Nojima
  3. RIKEN Center for Emergent Matter Science (CEMS), Wako 0351–0198, Japan.

    • Yoshihiro Iwasa

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Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Yoshihiro Iwasa.