School of Physics & Astronomy

Condensed Matter & Nanoscience Seminar

Monday 2nd November 2015 (13:00-14:00)

Andrea De Luca (Paris-Sud)


From quantum quenches to microwave refrigerator.The study of many-body quantum eigenstates has recently revealed a novel dynamical transition, dubbed many-body localization, intimately related to the mechanism of quantum thermalization and resulting from the competition between disorder and interaction. When the disorder becomes sufficiently strong, ergodicity is not ensured and standard thermodynamics does not apply. Here, we show manifestations of the weak/strong disorder regime in an open and driven quantum system. We consider a minimal model for Dynamic Nuclear Polarization (DNP), the most effective technique in NMR to increase nuclear polarization by doping a compound with unpaired electrons. These electron spins are subject to random fields and dipolar couplings, and are driven out-of-equilibrium by microwave irradiation. We show the emergence of two distinct dynamical phases: for strong interactions the irradiated electron spins behave as a thermal bath, cooling down the nuclear spins to their extremely low effective temperature. For weak interaction, hyperpolarization loses efficiency and the description in terms of an effective temperature breaks down.

School of Physics and Astronomy

The University of Nottingham
University Park
Nottingham NG7 2RD

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