Temperature-frequency scaling in amorphous niobium-silicon near the metal-insulator transition

Abstract

Millimeter-wave transmission measurements have been performed in amorphous niobium-silicon alloy samples where the DC conductivity follows the critical temperature dependence ${\sigma }_{dc}\propto T^{1/2}$. The real part of the conductivity is obtained at eight frequencies in the range 87--1040 GHz for temperatures 2.6 K and above. In the quantum regime ($\hslash \omega >k_{B}T$) the real part of the high-frequency conductivity has a power-law frequency dependence $Re\sigma (\omega )\propto {\omega }^{1/2}$. For temperatures 16 K and below the data exhibits temperature-frequency scaling predicted by theories of dynamics near quantum-critical points.

4 pages, 3 Postscript figures; revised version to be published in Physical Review Letters: changed several references, fixed typos, and reworded several paragraphs

References in corpus (2)

• Continuous Quantum Phase Transitions
• Non-zero temperature transport near quantum critical points

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