Two-Dimensional Weyl Material-Based Negative Quantum Capacitance Effect for a Steep-Slope Hysteresis-Free Switching Device

The emergence of Weyl physics and associated materials offers promising pathways to circumvent the fundamental limitation imposed by Boltzmann tyranny, a thermionic constraint governing the subthreshold slope that currently prevents further reduction of operating voltages and overall power dissipation in field-effect transistors (FETs) and related devices. In this work, an ultrathin Weyl material, WTe2, is utilized as a floating gate to achieve steep subthreshold (SS) hysteresis-free field-effect transistors based on the negative quantum capacitance (NQC) effect induced by the Weyl nodes. This device exhibits excellent performance in electrical characteristics, with a minimum SS of 20.3 mV/dec and an ultrasmall hysteresis of ∼2.6 mV. In addition, the optimal area ratio between WTe2 and the channel (MoS2) is found to be 1:1, and in this circumstance, a capacitance peak can be observed in the capacitance-voltage curve, suggesting the existence of the NQC effect. This effect is proposed to originate from the enhancement of the electron correlation effect as the Fermi level of WTe2 is tuned to approach the Weyl nodes, which presents a low carrier density of state. This work benefits the design of high integration density, energy-saving devices and provides a possible method of optimizing traditional devices by introducing Weyl physics.