TY - JOUR T1 - Non-Abelian eigenstate thermalization hypothesis JF - Phys. Rev. Lett. Y1 - 2023 A1 - Murthy, Chaitanya A1 - Babakhani, Arman A1 - Iniguez, Fernando A1 - Srednicki, Mark A1 - Nicole Yunger Halpern KW - FOS: Physical sciences KW - High Energy Physics - Theory (hep-th) KW - Quantum Gases (cond-mat.quant-gas) KW - Quantum Physics (quant-ph) KW - Statistical Mechanics (cond-mat.stat-mech) KW - Strongly Correlated Electrons (cond-mat.str-el) AB -

The eigenstate thermalization hypothesis (ETH) explains why chaotic quantum many-body systems thermalize internally if the Hamiltonian lacks symmetries. If the Hamiltonian conserves one quantity ("charge"), the ETH implies thermalization within a charge sector -- in a microcanonical subspace. But quantum systems can have charges that fail to commute with each other and so share no eigenbasis; microcanonical subspaces may not exist. Furthermore, the Hamiltonian will have degeneracies, so the ETH need not imply thermalization. We adapt the ETH to noncommuting charges by positing a non-Abelian ETH and invoking the approximate microcanonical subspace introduced in quantum thermodynamics. Illustrating with SU(2) symmetry, we apply the non-Abelian ETH in calculating local observables' time-averaged and thermal expectation values. In many cases, we prove, the time average thermalizes. However, we also find cases in which, under a physically reasonable assumption, the time average converges to the thermal average unusually slowly as a function of the global-system size. This work extends the ETH, a cornerstone of many-body physics, to noncommuting charges, recently a subject of intense activity in quantum thermodynamics.

VL - 130 UR - https://arxiv.org/abs/2206.05310 U5 - https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.140402 ER -