Voltage-Induced Bistability of Single Spin-Crossover Molecules in a Two-Dimensional Monolayer

Bistable spin-crossover molecules are particularly interesting for the development of innovative electronic and spintronic devices as they present two spin states that can be controlled by external stimuli. In this paper, we report the voltage-induced switching of the high spin/low spin electronic states of spin-crossover molecules self-assembled in dense 2D networks on Au(1 1 1) and Cu(1 1 1) by scanning tunneling microscopy at low temperature. On Au(1 1 1), voltage pulses lead to the nonlocal switching of the molecules from any-high or low-spin state to the other followed by a spontaneous relaxation toward their initial state within minutes. On the other hand, on Cu(1 1 1), single molecules can be addressed at will. They retain their new electronic configuration after a voltage pulse. The memory effect demonstrated on Cu(1 1 1) is due to an interplay between long-range intermolecular interaction and molecule/substrate coupling as confirmed by mechanoelastic simulations.