SEMINAR ANNOUNCEMENT “Propagation of an impurity through a quantum medium”

SEMINAR ANNOUNCEMENT
Wednesday, 4 th of July 2018 at 11:00
UPC campus nord, B4-212 (aula seminari)
Mikhail Zvonarev
Univ Paris-Sud, Laboratoire LPTMS, UMR8626, Orsay, F-91405, France
CNRS, Orsay, F-91405, France
“Propagation of an impurity through a quantum medium”
Abstract
I will report on recent theoretical and experimental progress in understanding
the dynamics of an impurity particle injected into a one-dimensional quantum
liquid. I will show that the momentum distribution of the impurity subject to
a constant external force exhibits characteristic Bragg reflections at the edge
of an emergent Brillouin zone. As a consequence, the impurity exhibits
periodic dynamics that is interpreted as Bloch oscillations, which arise even
though the quantum liquid is translationally invariant. I will also discuss a
quantum flutter phenomenon, whose essence is that the impurity injected into
a liquid with some initial momentum sheds only a part of it to the background
gas, and forms a correlated state that no longer decays in time; furthermore,
if the initial momentum is large enough, the impurity undergoes long-lived
oscillations. The value of the impurity's velocity at infinite time lies between
zero and the speed of sound in the gas, and is determined by the injection
protocol. This way, the impurity's frictionless motion is a dynamically
emergent phenomenon whose description goes beyond accounting for the
kinematic constraints of Landau's approach to superfluidity.