Special CMSP Seminar TUESDAY 23 February at 14:00 hrs

[Condensed Matter Section]

Special Seminar in
Condensed Matter Physics and Statistical Physics


TUESDAY 23 February at 14:00 hrs
EULER LECTURE HALL, Terrace Level, Leonardo building


Andrea DE LUCA (ENS - Lab. de Physique Theorique, Paris, France)

"The Importance of Being Ergodic: Cooling Down by Quantum Thermalization"


Abstract:
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. We show that at moderate 
disorder, nuclear spins equilibrate to the effective spin-temperature 
established among the electron spins of radicals, as expected from the 
quantum theory of thermalization. Interestingly, the highest 
polarization is reached at a point where the establishment of a spin 
temperature is just about to break down due to the incipient many-body 
localization transition in the electron spin system.