Negative Differential\nResistance with Ultralow Peak-to-Valley\nVoltage Difference in Td-WTe<sub>2</sub>/2H-MoS<sub>2</sub> Heterostructure

Negative differential resistance (NDR) devices with a\nlow peak-to-valley\nvoltage difference (Δ<i>V</i>) exhibit a high cut\noff frequency and low power consumption efficiency, which is significant\nfor fabricating high-performance oscillators. However, achieving an\nultralow Δ<i>V</i> is challenging. In this work, we\nreport the first construction of an NDR device utilizing a van der\nWaals heterostructure composed of semimetallic Td-WTe<sub>2</sub> and\nsemiconducting 2H-MoS<sub>2</sub>. Our findings reveal that the narrow\nenergy region of the decreasing density of states (DOS) above the\nFermi level of WTe<sub>2</sub> acts as a narrow band gap, facilitating\ntype-III band alignment with MoS<sub>2</sub> and enabling band-to-band\ntunneling-based NDR transport. Notably, the NDR device exhibits an\nultralow Δ<i>V</i> of approximately 0.01 V, which\nis at least an order of magnitude lower than previously reported values.\nThis work not only introduces a new approach for NDR device fabrication\nbut also provides new insights into the pivotal role of Td-WTe<sub>2</sub> in NDR transport.