Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 6: Solids At Low Temperature: Amorphous and Tunnel Systems, Glasses, ...
TT 6.3: Vortrag
Montag, 27. März 2006, 11:15–11:30, HSZ 105
Low temperature breakdown of coherent tunneling in amorphous solids by the nuclear quadrupole interaction — •Alexander Burin1, Peter Fulde2, and Ilya Polishchuk3 — 1Department of Chemistry, Tulane University, New Orleans, LA 70118, USA — 2Max-Planck-Institut fur Physik Komplexer Systeme, D-01187*Dresden, Germany — 3RRC Kurchatov Institute, Kurchatov Sq. 1, 123182 Moscow, Russia
We consider the effect of the internal nuclear quadrupole interaction on quantum tunneling of complex multi-atomic two-level systems. Two distinct regimes of strong and weak interactions are found. They depend on the relationship between the characteristic energy of the internal interaction λ∗, which is directly proportional to the number of tunneling atoms per tunneling system, and a bare tunneling coupling strength Δ 0. When Δ0>λ∗, the internal interaction is negligible and tunneling remains coherent, being defined by the strength of Δ0. When Δ0<λ∗, coherent tunneling breaks down and the effective tunneling amplitude decreases by an exponentially small overlap factor η∗≪1 between the internal ground states of the left and right well, affecting thermal and kinetic properties of tunneling systems. The theory is applied to interpret the anomalous behavior of the resonant dielectric susceptibility in amorphous solids for T≤5mK in terms of the nuclear quadrupole interaction. We suggest clarifying experiments using external magnetic fields to test the theories predictions and to shed some light on the internal structure of tunneling systems in amorphous solids.