Lattice Dynamics Driven by Tunneling Current in 1T′ Structure of Bilayer VSe₂

Interesting lattice dynamics were recently reported in 1T′ structure of bilayer VSe₂ attributed to the vibration of Se atoms, but it was limited to topographic observation using scanning tunneling microscopy (STM). We conduct further systematic STM study to understand the origin of lattice dynamics in bilayer VSe₂. Time spectroscopy of tunneling current is measured with the feedback loop disabled, while holding the position of the STM tip over a single Se atom. The time spectroscopy indeed shows random telegraph signals that tunneling current fluctuates between high and low currents. Such fluctuations of current reflect the vibrational motion of the Se atom. Statistical analysis described by the Markov process provides average residence time (τ) for high and low current states, and transition rate (R = 1/τ). Interestingly, the transition rate as a function of tunneling current (I) follows a power law of R = I^N (N = constant), and the N value is close to 1. This linearity of transition rate indicates that the lattice dynamics are mostly induced by tunneling current. Our result confirms the role of tunneling current that drives the observed lattice dynamics in the bilayer VSe₂.