Temporal universal conductance fluctuations in RuO${}_2$ nanowires due to mobile defects

Temporal universal conductance fluctuations (TUCF) are observed in RuO${}_2$ nanowires at cryogenic temperatures. The fluctuations persist up to very high $T\sim 10$ K. Their root-mean-square magnitudes increase with decreasing $T$, reaching $\sim 0.2e^2\mathrm{/}h$ at $T\lesssim 2$ K. These fluctuations are shown to originate from scattering of conduction electrons with rich amounts of mobile defects in artificially synthesized metal oxide nanowires. TUCF characteristics in both one-dimensional saturated and unsaturated regimes are identified and explained in terms of current theories. Furthermore, the TUCF as a probe for the characteristic time scales of the mobile defects (two-level systems) are discussed.