Anomalous Shot Noise in Nanowires of Spin Hall Material b-Ta

Beta allomorph of Ta exhibits a large spin Hall effect (SHE), enabling its extensive applications in spin-orbitronics. It is also a “bad” metal whose high resistivity nearly satisfies the Ioffe-Regel criterion for localization and slightly increases as temperature T decreases. However, in the absence of resistivity divergence at low T, the electronic properties of b-Ta cannot be explained by single-particle hopping. To elucidate its electronic state, we study the electronic shot noise produced by the nanowires of b-Ta. The noise exhibits a strong dependence on temperature and is suppressed compared to the expectations for quasiparticle diffusion. While hopping can suppress noise, this mechanism is ruled out by the analysis of scaling with the nanowire length and small thermal broadening of noise dependence on bias. These anomalous features closely resemble those of strange metal nanowires, which were attributed to the correlated electron liquid state [L. Chen et al., Science 382, 907–911 (2023)]. Our results suggest that electron-electron interaction dominates electronic properties of b-Ta, challenging the single-particle interpretation of its SHE.