Transconductance as a Probe of Valley Thermodynamics in Multilayer WSe₂

2026/05/31 by Katsunori Wakabayashi, Souren Adhikary, Tomoaki Kameda · 2 citations
Physics and Astronomy · #cond-mat.mes-hall #cond-mat.mtrl-sci

paper · pdf · doi:10.1103/xsr9-l7ll

published as Phys. Rev. B 114, 115403 (2026) · 8 pages; 4 figures

arxiv created 2026/06/23 · arxiv updated 2026/08/07

Abstract

Transconductance is a central figure of merit in field-effect transistors, typically governed by charge accumulation and carrier mobility. In multilayer WSe₂ transistors, however, it is shown to carry a nonlinear transport signature of inter-valley carrier redistribution between the K and Γ valleys. This valley-crossover contribution suppresses transconductance in bilayer WSe₂ and reverses sign in trilayer, while remaining absent in single-valley systems. Unlike extrinsic mechanisms such as trap-state filling or contact resistance, the anomaly leaves the subthreshold swing unchanged and cannot be reproduced within conventional single-valley transport models. Introducing the valley susceptibility χ_v ≡ ∂ f_Γ/∂ V_{\rm GS}, bounded by an intrinsic thermodynamic limit (4k_BT)^-1, we quantify this response and show that it reaches ∼0.20 V^-1 in bilayer WSe₂ near threshold at room temperature. The sign, magnitude, and temperature dependence of the anomaly provide directly measurable fingerprints of valley thermodynamics, establishing transconductance as an electrical probe of internal electronic degrees of freedom and revealing a previously hidden nonlinear response in standard transistor measurements.

Citations

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