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UID:0-750@lptms.universite-paris-saclay.fr
DTSTART;TZID=Europe/Paris:20201124T110000
DTEND;TZID=Europe/Paris:20201124T120000
DTSTAMP:20201118T225104Z
URL:https://www.lptms.universite-paris-saclay.fr/seminars/seminaire-du-lpt
 ms-mikhail-zvonarev/
SUMMARY:Séminaire du LPTMS : Mikhail Zvonarev (LPTMS) - LPTMS (100% online
  seminar) - 24 Nov 20 11:00
DESCRIPTION:Mobile impurity in a quantum fluid\nMikhail Zvonarev (LPTMS)\n\
 nOnline seminar --- ZOOM Meeting ID: 994 9374 5810 -- Password: 467383 --\
 n\nI am planning to discuss several recent findings (theoretical and exper
 imental) in the dynamics of an impurity particle injected into a quantum l
 iquid:\n\n(i) The momentum distribution of the impurity in one dimension s
 ubject to a constant external force exhibits characteristic Bragg reflecti
 ons at the edge of an emergent Brillouin zone. As a consequence\, the impu
 rity exhibits periodic dynamics that is interpreted as Bloch oscillations\
 , which arise even though the quantum liquid is translationally invariant.
 \n\n(ii) The impurity injected into a one-dimensional liquid with some ini
 tial 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 init
 ial momentum is large enough\, the impurity undergoes long-lived oscillati
 ons. The value of the impurity's velocity at infinite time lies between ze
 ro 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 e
 mergent phenomenon whose description goes beyond accounting for the kinema
 tic constraints of Landau's approach to superfluidity.\n\n(iii) The impuri
 ty traveling through a weakly interacting three-dimensional Bose-Einstein 
 condensate (BEC) of ultra-cold atoms shows a phase transition in the groun
 d state and far-from-equilibrium properties of the system as a function of
  the impurity's velocity. Above a critical initial velocity\, the impurity
 's final velocity reaches a fundamental kinematic boundary\, the BEC's spe
 ed of sound. For weak and intermediate impurity-BEC interactions\, the cri
 tical line is determined by the effective mass of the polaron. This quantu
 m transition can be interpreted as a dynamical Cherenkov effect\; the impu
 rity-BEC interaction causes the dynamics of the system to appear as if the
  bare impurity is propagating through a BEC whose speed of sound is altere
 d by an effective refractive index.
CATEGORIES:seminars
LOCATION:LPTMS (100% online seminar)\, LPTMS - Bâtiment Pascal n° 530 rue
  André Rivière - Université Paris-Saclay\, Orsay\, 91405\, France
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=LPTMS - Bâtiment Pascal n
 ° 530 rue André Rivière - Université Paris-Saclay\, Orsay\, 91405\, Fr
 ance;X-APPLE-RADIUS=100;X-TITLE=LPTMS (100% online seminar):geo:0,0
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