Relaxation Dynamics of an Isolated Large-Spin Fermi Gas Far from Equilibrium

Abstract

A fundamental question in many-body physics is how closed quantum systems reach equilibrium. We address this question experimentally and theoretically in an ultracold large-spin Fermi gas where we find a complex interplay between internal and motional degrees of freedom. The fermions are initially prepared far from equilibrium with only a few spin states occupied. The subsequent dynamics leading to redistribution among all spin states is observed experimentally and simulated theoretically using a kinetic Boltzmann equation with full spin coherence. The latter is derived microscopically and provides good agreement with experimental data without any free parameters. We identify several collisional processes that occur on different time scales. By varying density and magnetic field, we control the relaxation dynamics and are able to continuously tune the character of a subset of spin states from an open to a closed system.

Universal Spin Transport and Quantum Bounds for Unitary Fermions

“…Spin waves. Spin waves have been studied extensively in both Bose and Fermi gases (21,22,24,(30)(31)(32)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52). Transverse spin waves arise from the identical spin rotation effect (ISRE, see §2.1.2 below).…”

Coherent Heteronuclear Spin Dynamics in an Ultracold Spinor Mixture

“…So far, a rich variety of phenomena have been explored experimentally, including spin oscillations in spinor Bose-Einstein condensate (BEC) [2][3][4][5][6][7][8][9][10] and in thermal Bose gases [11], as well as various types of spin textures [12][13][14][15]. Very recently, coherent spin oscillations in a spinor Fermi gas [16] and its relaxation [17] have been investigated.…”

Investigation of Feshbach resonances in ultracold K40 spin mixtures

“…Feshbach resonances have been found in many bosonic as well as fermionic atomic systems (see [1][2][3][4][5] and references therein). The isotope 40 K constitutes one of the work horses in current experiments with ultracold fermions and provides a rich ground-state structure allowing for the realization of binary and multi-component spin mixtures [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] as well as several Bose-Fermi [24][25][26][27][28][29][30] and Fermi-Fermi mixtures [31][32][33][34][35]. In the energetically-lowest hyperfine manifold with total angular momentum f = 9/2 ten magnetic spin states are available ranging from m = −9/2, .…”

“…The collision channel {+1/2, −1/2} is of particular interest. It is the magnetic ground state of the spin subspace with zero magnetization M = m 1 + m 2 = 0 and, hence, losses due to inelastic two-body collisions can only occur by spin-relaxation from the weak magnetic dipoledipole interactions [23]. In this mixture, we have located a Feshbach resonance at B calc res = 389.6 G with a width of ∆B calc = 26.4 G, which is about three times larger than the width of the commonly used Feshbach resonances in From an experimental point of view, a broad resonance is desirable as it lowers the technical demands for setting a stable value of the interaction strength close to resonance.…”