title: Memristive phase switching in two-dimensional 1T-TaS2 crystals.
abstract: Scaling down materials to an atomic-layer level produces rich physical and chemical properties as exemplified in various two-dimensional (2D) crystals including graphene, transition metal dichalcogenides, and black phosphorus. This is caused by the dramatic modification of electronic band structures. In such reduced dimensions, the electron correlation effects are also expected to be significantly changed from bulk systems. However, there are few attempts to realize novel phenomena in correlated 2D crystals. We report memristive phase switching in nano-thick crystals of 1T-type tantalum disulfide (1T-TaS2), a first-order phase transition system. The ordering kinetics of the phase transition were found to become extremely slow as the thickness is reduced, resulting in an emergence of metastable states. Furthermore, we realized unprecedented memristive switching to multistep nonvolatile states by applying an in-plane electric field. The reduction of thickness is essential to achieve such nonvolatile electrical switching behavior. The thinning-induced slow kinetics possibly make the various metastable states robust and consequently realize the nonvolatile memory operation. The present result indicates that a 2D crystal with correlated electrons is a novel nano-system to explore and functionalize multiple metastable states that are inaccessible in its bulk form.
authors.affiliation: Quantum-Phase Electronics Center and Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
authors.forename: Masaro
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Quantum-Phase Electronics Center and Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Suzuki
authors.affiliation: Quantum-Phase Electronics Center and Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
authors.forename: Yijin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Quantum-Phase Electronics Center and Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Nakano
authors.affiliation: Quantum-Phase Electronics Center and Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan. ; RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Iwasa
keywords: Tantalum disulfide (TaS2); electrical phase switching; first-order phase transition; memristor; metastable states; nonvolatile memory; two-dimensional materials