Dear group
The soccer semi final between Mexico and Germany is tomorrow 2-4 PM. I will
be watching it in the TV upstairs in the department center. Don't kill me
for moving group meeting at 4 people :) anybody that wants to come to watch
the game, can come troll me as I suspect that Flo and Christoph will be
victorious tomorrow and take revenge for Semion whose Russia was beat by
Mexico on Saturday.
See you all at group meeting at 4 tomorrow if not earlier ;)
Alan
On Wed, Jun 28, 2017 at 6:07 PM Ian Kivlichan <ian.kivlichan(a)gmail.com>
wrote:
Hi all,
Tomorrow David will talk at group meeting. See below for his title and
abstract.
All the best,
Ian
-----------------
Title: Effective working fluid-bath decoupling at the strong coupling
regime
Abstract: Heat machines in the strong coupling regime have been proposed
to study fundamental thermodynamics questions, and to improve upon the low
power produced by the weak coupling counterpart. At weak coupling, the
power is proportional to the square of the coupling strength. A fair
hypothesis may be that an increase of the coupling strength will produce an
increase on the machine output. However, studies of a wide range of
different heat machines predict an effective decoupling between the working
fluid and strongly coupled baths, reducing the machine output to levels
comparable to the weak coupling regime. This effect has been predicted for
fermonic and bosonic baths and for a wide range of working fluids that
includes single and multiple spins or harmonic oscillator and molecular
systems. A diverse variety of theoretical methods has been applied to these
models, including the polaron transformation, Holstein Primakoff
transformation, non-interacting blip approximation (NIBA), surrogate
Hamiltonian approach and reaction coordinate mapping. The wide range of
systems and methods shows that the effective decoupling is not an artifact
of some approximation, which in turn may indicate that the effective
decoupling is a universal property of the strong coupling regime,
regardless of the character of the bath, the working fluid or the
interaction between them.
We continue the exploration of this universality question by studying
different heat machines composed of a spin working fluid that interacts
with spin baths. In order to better understand strong coupling effects, we
first analyze a toy model of a small spin bath and use numerical
calculations to extend our results to larger spin baths. Besides addressing
the question of universality, and the underlying physical mechanism that
produces the working fluid-bath decoupling, we study methods to avoid the
effective decoupling by adding an external decoherence source to the spin
baths.
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Alán Aspuru-Guzik | Professor of Chemistry and Chemical Biology
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