Condensed Matter Physics Seminar
Speaker: Victor Galitski, University of Maryland
Title: Quantum friction effects in superfluids
Refreshments available at 3:45 pm.
Date: Mon, 02 Oct 2017, 4:10 pm – 5:10 pm
Location: 1400 BPS Bldg.
Low-temperature ordered states of matter with spontaneously broken symmetry host collective excitations – Goldstone modes – that are coupled to the order parameter field. The collective excitations act on the order parameter as a thermal bath and give rise to its non-trivial dynamics that include effects like “quantum friction,” a stochastic Langevin force and effective Brownian motion. In this talk, I will discuss new theoretical and experimental results and ideas on such quantum friction effects in superfluids and magnetic systems. In the first part of my talk, I will focus on quantum dynamics of topological textures, in particular solitons/domain walls, propagating in low-dimensional superfluids/magnets. An effective quasi-classical equations of motion will be derived. It will be shown that interestingly the familiar Ohmic friction is absent in the integrable setup, but the equations contain non-Markovian dissipative forces . I will explain a way to restore and control the Ohmic friction force and related Brownian motion of topological textures, as was demonstrated in a recent experiment .
 D. Efimkin, J. Hofmann, and V. Galitski, “Non-Markovian quantum friction of bright solitons in superfluids,” Phys. Rev. Lett. 116, 225301 (2016)
 L. Ayckock et al., “Brownian motion of solitons,” Proc. Nat. Acad. Sciences 114, 2503 (2017)