Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 30: Postersitzung IV: Kritische Ph
änomene, Quantenstörstellen, niederdimensionale Systeme
TT 30.15: Poster
Donnerstag, 11. März 2004, 14:30–19:00, Poster A
Observation of non-Gaussian conductance fluctuations at low temperatures in Si:P(B) at the metal-insulator transition — •Swastik Kar1, A. K. Raychaudhuri1, Arindam Ghosh2, H. v. Löhneysen3, and G. Weiss3 — 1Department of Physics, Indian Institute of Science, Banaglore 560012, India — 2Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom — 3Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe, Germany
Conductance fluctuation(noise) has been one of the most studied areas in condensed matter. Of considerable interest is the behavior of noise near the the Anderson-Mott metal-insulator transition (MIT). In this report we present the results of the first extensive experimental investigations of non-Gaussian conductance fluctuations in a bulk (3-D) system (single crystals of P-doped Si) as it is driven through the MIT at low temperatures (T<20K). As T→0 and the system crosses over to the insulating regime, the scaled magnitude of noise, γH, increases with decrease in temperature following an approximate power-law γH ∼ T−β. At low temperatures, γH diverges as n decreases through the critical concentration nc, accompanied by a growth of low-frequency spectral weight. The second spectrum and the Probability Density of the fluctuations show strong non-Gaussian behavior below 20K as n/nc decreases through 1. This has been interpreted as the onset of a glassy freezing of the electronic system across the transition.