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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:Relaxation to Equilibrium and Emergence of Long-ra
nge Order in a Two-Dimensional Quantum Vortex Gas
- Hayder Salman (University of East Anglia)
DTSTART;TZID=Europe/London:20221206T113000
DTEND;TZID=Europe/London:20221206T120000
UID:TALK183773AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/183773
DESCRIPTION:We study the relaxation of a two-dimensional (2D)
ultracold Bose gas from a nonequilibrium initial s
tate containing vortex excitations in experimental
ly realizable traps. We show that the subsystem o
f vortex gas excitations results in the spontaneou
s emergence of a coherent superfluid flow with a n
onzero coarse-grained vorticity field. The stream
function of this emergent quasiclassical 2D flow i
s governed by a Poisson-Boltzmann equation. Numer
ical simulations of a neutral point vortex model a
nd a Bose gas governed by the 2D Gross-Pitaevskii
equation in a square trap reveal that a large-scal
e flow field with net angular momentum emerges tha
t is consistent with predictions of the Poisson-Bo
ltzmann equation. The theory presented is subsequ
ently verified in recent experimental work focusin
g on the turbulent relaxation dynamics of a two-di
mensional chiral vortex gas. Using carefully desig
ned experimental forcing protocols to inject vorti
ces into the system\, we are able torealize equil
ibria spanning the full phase diagram of the vorte
x gas\, including vortex states near zero temperat
ure\, infinite temperature\, and negative absolu
te temperatures. The resulting experimentally meas
ured long-time vortex distributions are found to b
e in excellent agreement with the mean-field predi
ctions of the Poisson Boltzmann equation. This all
ows us to verify that\, during the relaxation dyna
mics\, the vortex excitations evolve to a state th
at maximises the entropy of the vortex gas.
LOCATION:Seminar Room 1\, Newton Institute
CONTACT:
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