Microscopic phase-transition framework for gate-tunable superconductivity in monolayer WTe2

Abstract

The recently reported gate-tunable superconductivity in monolayer WTe2 [Science 362, 922 (2018); Science 362, 926 (2018); Nat. Phys. 20, 269 (2024); Phys. Rev. Res. 7, 013224 (2025)] exhibits several striking anomalies beyond the standard paradigm, including a contrasting carrier-density dependence of the transition temperature Tc in weakly and strongly disordered regimes, and more surprisingly, the sudden disappearance of superconducting fluctuations below a critical carrier density. To understand these features, we go beyond mean-field theory and develop a microscopic framework that treats the gap and superfluid density by explicitly and self-consistently incorporating both Nambu-Goldstone (NG) phase fluctuations and Berezinskii-Kosterlitz-Thouless (BKT) fluctuations. We show that these fluctuations are minimal in the weak-disorder regime but become crucial under strong disorder, where the zero-temperature gap renormalized by NG quantum fluctuations becomes density-dependent while the BKT fluctuations drive the Tc below the gap-closing temperature. Simulations within this unified framework combined with the density-functional-theory input to account for the excitonic instability quantitatively reproduced nearly all key experimental observations, providing a consistent understanding of reported anomalies.

Source-reported materials — not catalogue approval

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