title: Metallic ground state in an ion-gated two-dimensional superconductor.
abstract: Recently emerging two-dimensional (2D) superconductors in atomically thin layers and at heterogeneous interfaces are attracting growing interest in condensed matter physics. Here, we report that an ion-gated zirconium nitride chloride surface, exhibiting a dome-shaped phase diagram with a maximum critical temperature of 14.8 kelvin, behaves as a superconductor persisting to the 2D limit. The superconducting thickness estimated from the upper critical fields is ≅ 1.8 nanometers, which is thinner than one unit-cell. The majority of the vortex phase diagram down to 2 kelvin is occupied by a metallic state with a finite resistance, owing to the quantum creep of vortices caused by extremely weak pinning and disorder. Our findings highlight the potential of electric-field-induced superconductivity, establishing a new platform for accessing quantum phases in clean 2D superconductors.
authors.affiliation: Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Saito
authors.affiliation: Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan. Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kasahara
authors.affiliation: Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan. Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands. RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.
authors.forename: Jianting
authors.initials: J
authors.lastname: Ye
authors.affiliation: Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan. RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Iwasa
authors.affiliation: Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nojima