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TT: Fachverband Tiefe Temperaturen

TT 11: Transport: Nanoelectronics I - Quantum Dots and Wires, Point Contacts 2

TT 11.7: Vortrag

Montag, 23. März 2009, 15:45–16:00, HSZ 301

1D to 0D crossover of decoherence time in small mesoscopic rings — •Maximilian Treiber¹, Oleg Yevtushenko¹, Florian Marquardt¹, Igor V. Lerner², and Jan von Delft¹ — ¹Physics Department, ASC, and CeNS, LMU, Theresienstrasse 37, 80333 Munich, Germany — ²School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom

We study the decoherence time τ_φ(T) in a disordered quasi 1D ring weakly coupled to leads, in the low temperature regime where decoherence is governed by electron interactions. We employ a path integral approach which is free of IR singularities and reproduces the known power-law dependence τ_φ ∼ T^−a, where a=2/3 or 1 for the diffusive (τ_φ E_c 1, where E_c is the Thouless energy) [1] or ergodic (τ_φ E_c ≥ 1) [2] regimes, respectively. By incorporating the Pauli principle into the Nyquist noise correlation function, thus excluding large energy transfers (ω T), we are able to also describe the dimensional crossover of τ_φ from 1D to 0D as T is lowered below E_c, causing the exponent to change to a=2. The ∼ T⁻² dependence has been predicted before [3], but has so far eluded direct observation. We point out that in the ring geometry it is possible to measure it not only via the smooth part of the magnetoresistance but also via the amplitude of the Altshuler-Aronov-Spivak oscillations.

[1] B. L. Altshuler et al., J. Phys. C, 15, 7367 (1982).

[2] C. Texier and G. Montambaux, Phys. Rev. B 72, 115327 (2005);

   T. Ludwig and A. D. Mirlin, Phys. Rev. B 69, 193306 (2005).

[3] U. Sivan et al., Europhys. Lett. 28, 115 (1994).