arXiv subjects

An-Shao Lien

Publications and source records attributed to An-Shao Lien.

3 recordsLinked to original sources

arXiv2020

Oxygen vacancy-driven orbital multichannel Kondo effect in Dirac nodal line metals IrO2 and RuO2

Strong electron correlations have long been recognized as driving the emergence of novel phases of matter. A well recognized example is high-temperature superconductivity which cannot be understood in terms of the standard weak-coupling theory. The exotic properties that accompany the formation of the two-channel Kondo effect including the emergence of an unconventional metallic state in the low-energy limit also originate from strong electron interactions. Despite its paradigmatic role for the formation of non-standard metal behavior, the stringent conditions required for its emergence have made the observation of the nonmagnetic, orbital two-channel Kondo effect in real quantum materials difficult, if not impossible. We report the observation of orbital one- and two-channel Kondo physics in the symmetry-enforced Dirac nodal line metals IrO2 and RuO2 nanowires and show that the symmetries that enforce the existence of Dirac nodal lines also promote the formation of nonmagnetic Kondo correlations. Rutile oxide nanostructures thus form a versatile quantum matter platform to engineer and explore intrinsic, interacting topological states of matter.

cond-mat.str-el↗

arXiv2011

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 $\sim 0.2 e^2/h$ 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.

cond-mat.mes-hall↗

arXiv2010

Long electron dephasing length and disorder-induced spin-orbit coupling in indium tin oxide nanowires

We have measured the quantum-interference magnetoresistances in two single indium tin oxide (ITO) nanowires between 0.25 and 40 K, by using the four-probe configuration method. The magnetoresistances are compared with the one-dimensional weak-(anti)localization theory to extract the electron dephasing length $L_ϕ$. We found, in a 60-nm diameter nanowire with a low resistivity of $ρ$(10 K) = 185 $μΩ$ cm, that $L_ϕ$ is long, increasing from 150 nm at 40 K to 520 nm at 0.25 K. Therefore, the nanowire reveals strict one-dimensional weak-localization effect up to several tens of degrees of Kelvin. In a second 72-nm diameter nanowire with a high resistivity of $ρ$(10 K) = 1030 $μΩ$ cm, the dephasing length is suppressed to $L_ϕ$(0.26 K) = 200 nm, and thus a crossover of the effective device dimensionality from one to three occurs at about 12 K. In particular, disorder-induced spin-orbit coupling is evident in the latter sample, manifesting weak-antilocalization effect at temperatures below $\sim$ 4 K. These observations demonstrate that versatile quantum-interference effects can be realized in ITO nanowires by controlling differing levels of atomic defects and impurities.

cond-mat.mes-hall↗