Dynamical Quantum Phase Transitions

Anatoli Polkovnikov (Boston U.)
Event Date and Time: 
Thu, 2018-01-11 16:00 - 17:00
Henning 201
Intended Audience: 

Phase transitions are usually defined through emergence of singularities of free
energy of the system with changing some external parameter like temperature.
Familiar examples include liquid-gas transitions, or transitions between
paramagnetic and ferromagnetic phases. Quantum phase transitions are very similar
except that they occur at zero temperature and are driven by quantum fluctuations.
In this talk I will introduce a concept of dynamical quantum phase transitions,
where the role of parameter driving the system between different phases is played by
the evolution time following some dynamical process like a quench. Mathematically
these transitions can be understood through singularities of the Loschmidt type
return amplitude, which serves as a natural real time generalization of the
partition function. Physically these transitions are related to the singularities in
the work distribution function. These transitions are naturally explained though the
language of zeros of the return amplitude in the complex time plane, which are
similar to Fisher zeros of the partition function in the complex temperature plane
in equilibrium systems.

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