Torque-controlled stochastic switching in single-molecule devices

Probabilistic switching devices, as an emerging class of electronic components enabling stochastic transitions between binary states, offer unique prospects for stochastic computing tasks including true random number generation, Monte Carlo simulation, and Bayesian inference. In this study, leveraging the inherent Boltzmann-distributed output of molecular devices at thermal equilibrium and their high sensitivity to external fields, a torque-controlled single-molecule stochastic switch is demonstrated at room temperature. This device comprises an aminoalkyl-functionalized zinc complex with an orthogonal dipole moment, which is covalently bridged between graphene electrodes. Through synergistic coupling of molecular dipole with an external electric field, an asymmetric torque is induced, driving controlled conformational changes under steric confinement and enabling programmable stochastic switching between high- and low-conductance states. The output probability is precisely tunable via bias voltage modulation, exhibiting the characteristic sigmoidal response of probabilistic devices. Furthermore, temperature-dependent experiments map the free-energy landscape of the molecular probabilistic switch. This insight facilitates the rational design of stable and controllable probabilistic devices working under ambient conditions.