Phase-selective orbital-charge conversion in $\mathrm{MoT}{\mathrm{e}}_2$

Abstract

Two-dimensional transition metal dichalcogenides (TMDs) have emerged as promising materials for spin--orbitronics owing to their strong spin--orbit coupling and rich electronic phases. However, their orbital transport properties remain largely unexplored. Here, we demonstrate that the orbitronic response of $\mathrm{MoT}{\mathrm{e}}_2$ is governed by a thickness-driven structural phase transition. RF-sputtered $\mathrm{MoT}{\mathrm{e}}_2$ thin films exhibit a crossover at a critical thickness of approximately $4.5\mathrm{nm}$, stabilizing in the metallic $1T^{\prime }$ phase below this threshold and in the semiconducting $2H$ phase above it. Raman spectroscopy and scanning tunneling spectroscopy (STS) confirm the structural and electronic transition, revealing gapless behavior in ultrathin films and a finite band gap in thicker samples. Spin-pumping measurements detect an additional transverse charge-conversion signal exclusively in metallic $1T^{\prime }$-$\mathrm{MoT}{\mathrm{e}}_2$, in agreement with first-principles calculations that identify a dominant orbital Rashba--Edelstein response as the underlying conversion mechanism.

15vpages, 4 figures