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Title: Thermalization and localization in isolated many-body quantum systems
Authors: Morningstar, Alan
Advisors: Huse, David
Contributors: Physics Department
Keywords: dynamics
Subjects: Condensed matter physics
Quantum physics
Statistical physics
Issue Date: 2022
Publisher: Princeton, NJ : Princeton University
Abstract: On long length and time scales, an isolated many-body quantum system can either settle into a thermal equilibrium under its own internal dynamics, i.e., thermalize, or it can remain out of equilibrium indefinitely due to some mechanism for localization. When thermalization does occur, we can ask about how the system approaches its final equilibrium; when it does not, we can study the responsible mechanism for localization. The two possibilities can be separated by unconventional phase transitions or crossovers, and how localization gives way to thermalization at these boundaries is of fundamental interest. This dissertation is a collection of works on such topics. In Ch. 1, I provide some context for the research presented in the self-contained chapters that follow. Ch. 2 uses thermalization under periodic driving (Floquet) as an arena in which to test new computational methods. There we show that Tensor Processing Units—hardware built for large-scale machine-learning tasks—can be repurposed as a state-of-the-art platform for simulating quantum dynamics. In Ch. 3, we advance our understanding of the thermalization of Floquet systems by mapping out a phase diagram of the distinct behaviors that can be present in finite-size systems. Ch. 4 describes a joint theoretical/experimental study, in which we discover a new class of emergent hydrodynamics present in “tilted” lattice systems. This hydrodynamics contains a regime of emergent dipole-moment (center of mass) conservation. In Ch. 5 we impose exact dipole-moment conservation in a microscopic model and study a novel phase transition between a phase that thermalizes and one that does not. Chs. 6 and 7 explore two distinct regimes of many-body localization (MBL): In Ch. 6 we present an analytically solvable renormalization-group model of the MBL phase transition at asymptotically large length and time scales, showing that it may lie in a new universality class. Then, in Ch. 7 we focus on small systems in the MBL regime accessible to numerical and experimental studies. There we lay down several well separated “landmarks”, having to do with rare many-body resonances and so-called thermal avalanches, that exist within the crossover between the thermal and MBL regimes.
Alternate format: The Mudd Manuscript Library retains one bound copy of each dissertation. Search for these copies in the library's main catalog:
Type of Material: Academic dissertations (Ph.D.)
Language: en
Appears in Collections:Physics

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