Dresden 2003 – wissenschaftliches Programm
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SYQD: Quantum decoherence in solid state physics
SYQD 1: Quantum Decoherence in Solid State Physics I
SYQD 1.4: Hauptvortrag
Dienstag, 25. März 2003, 15:30–16:00, HSZ/01
Energy and Phase Relaxation in Mesoscopic Metal Wires — •Norman O. Birge — Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-1116, USA
At low temperatures, conduction electrons in disordered metals maintain phase coherence over times often exceeding one nanosecond. There is currently a controversy concerning the very low temperature behavior of the phase coherence time, τφ in weakly-disordered metals. The standard theories of electron-electron scattering predict that for T → 0 it should diverge as a power law of temperature. Many experiments, however, show a saturation of τφ at temperatures below 1 K [1]. It is important to ascertain whether those experimental observations reflect a fundamental, intrinsic decoherence mechanism, or an extrinsic, sample-dependent source of decoherence.
I will discuss two different experimental approaches to inelastic electron scattering. To determine τφ we measure the weak localization contribution to the magnetoresistance of narrow wires or the Aharonov-Bohm resistance oscillations of micron-sized rings [2]. To determine the rate of energy exchange between electrons we measure the shape of the electron energy distribution function when the sample is far from equilibrium [3]. By studying the effects of an applied magnetic field on these two kinds of experiments, we have learned that very dilute magnetic impurities can easily dominate both electron decoherence and energy exchange, even at concentrations of 1 part per million or less.
[1] P. Mohanty, E.M.Q. Jariwala, and R.A. Webb, Phys. Rev. Lett. 78, 3366 (1997).
[2] F. Pierre and N.O. Birge, Phys. Rev. Lett. 89, 206804 (2002); F. Pierre et al., submitted.
[3] H. Pothier et al., Phys. Rev. Lett. 79, 3490 (1997); A. Anthore et al., cond-mat/0109297.
Work performed in collaboration with F. Pierre and A. Gougam at MSU, and A. Anthore, H. Pothier, and D. Esteve at CEA Saclay, France. Supported by NSF DMR 0104178.