Quantum interference effects and electrical conduction in disordered metals
Abstract
We have conducted a series of experiments on thin, disordered metallic films made from a number of different materials, which were aimed at investigating for time dependent conductance fluctuations at low temperatures. The materials included in our survey were Pt, AuPd, Sb, Ag and Bi. Values of the phase breaking length, $L\sb{\phi}$, which is important in theoretical calculations, were determined from weak localization theory in conjunction with magneto-resistance measurements. Large co-deposited films (typically 50 $\mu$m $\times$ 10,000 $\mu$m) were used as references for system noise and other systematic effects. Samples used in the fluctuation studies were as small as 0.5 $\mu$m $\times$ 0.5 $\mu$m and were made with photo-lithography. The temperature range for this survey was from $\approx$50 mK to $\approx$10K. We have observed conductance fluctuations in samples of Pt, Ag and Bi. Two types of phenomenon were found: single, discrete jumps in the resistance of possibly long duration time (many hours), similar to random telegraph noise, and much faster broad band noise. Comparisons with theories by Feng, Lee, and Stone, and Al'tshuler and co-workers show excellent agreement. Significant conductance fluctuations were not observed in AuPd and Sb samples. However, more extensive experiments are needed with these two materials to show conclusively that no mechanisms are available for producing conductance fluctuations.
Degree
Ph.D.
Advisors
Giordano, Purdue University.
Subject Area
Condensation
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