# Condensed Matter Seminar Series

## Algebraic versus Exponential Decoherence in Dissipative Many-Particle Systems

### Thomas Barthel

#### LPTMS Orsay, France

##### Tuesday April 22, 9:15 am, Room 298, Physics Building

Abstract:
Ultimately, every quantum system of interest is coupled to some form of
environment which leads to decoherence. Until our recent study, it was
assumed that, as long as the environment is memory-less (i.e.
Markovian), the temporal coherence decay is always exponential-- to
such a degree that this behavior was synonymously associated with
decoherence. However, the situation can change if the system itself is
a many-body system. In this case, the interplay between dissipation and
internal interactions gives rise to a wealth of novel phenomena. In
particular, we have discovered recently that the coherence decay can
change to a power law.

After recapitulating the mathematical
framework and basic notions of decoherence, I will discuss an open XXZ
chain for which the decoherence time diverges in the thermodynamic
limit. The coherence decay is then algebraic instead of exponential. In
contrast, decoherence in the open transverse-field Ising model is found
to be always exponential. In this case, the internal interactions can
both facilitate and impede the environment-induced decoherence. The
results are based on quasi-exact simulations using a matrix product
representation of the density operator (time-dependent density matrix
renormalization group) and explained on the basis of perturbative
treatments.

Reference: Z. Cai and T. Barthel, PRL 111, 150403 (2013)

*Host: Harold Baranger*