Non-equilibrium Strongly Interacting Quantum Many-body Systems
Non-equilibrium Strongly Interacting Quantum Many-body Systems

Author: Oscar Leonardo Acevedo Pabón

Publisher:

Published: 2015

Total Pages:

ISBN-13:

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This thesis dissertation concerns the quantum dynamics of strongly interacting many-body systems under several non-equilibrium scenarios. Mimicking many real life settings, and specially some current major experiments, during most of this work we will deal with symmetrical interactions among the components, which will generate collective dynamics with high degree of correlation. The focus all throughout this work has been on the posssibility of accurately control the quantum properties of the system, even at the microscopic level, by cleverly choosing macroscopic manipulation protocols. Our main results can be summarized as follows. First, we thoroughly investigate the irreversible defect formation when the Dicke model, a paradigmatic light-matter system, is made to cross its quantum phase transition (QPT). Furthermore, we have been able to explain this dynamical QPT for totally connected lattices, which had remained unresolved by well-known theories like the Kibble-Zurek mechanism. This was done by means of a broad encompassing critical function theory. Also, by going beyond semi-adiabatic evolutions, we have discovered that the dynamical QPT of the Dicke model has an intermediate regime where non-equilibrium process provide a huge enhancing of quantum properties, far beyond the capabilities of equilibrium, quasi-equilibrium, or sudden quench schemes. Finally, we provided theoretical evidence and insights for the possibilities of quantum magnetism interactions in current high precision alkaline earth atom lattice clocks.

Quantum Many-Body Physics in Open Systems: Measurement and Strong Correlations
Quantum Many-Body Physics in Open Systems: Measurement and Strong Correlations

Author: Yuto Ashida

Publisher: Springer Nature

Published: 2020-01-06

Total Pages: 228

ISBN-13: 9811525803

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This book studies the fundamental aspects of many-body physics in quantum systems open to an external world. Recent remarkable developments in the observation and manipulation of quantum matter at the single-quantum level point to a new research area of open many-body systems, where interactions with an external observer and the environment play a major role. The first part of the book elucidates the influence of measurement backaction from an external observer, revealing new types of quantum critical phenomena and out-of-equilibrium dynamics beyond the conventional paradigm of closed systems. In turn, the second part develops a powerful theoretical approach to study the in- and out-of-equilibrium physics of an open quantum system strongly correlated with an external environment, where the entanglement between the system and the environment plays an essential role. The results obtained here offer essential theoretical results for understanding the many-body physics of quantum systems open to an external world, and can be applied to experimental systems in atomic, molecular and optical physics, quantum information science and condensed matter physics.

Strongly Interacting Quantum Systems out of Equilibrium
Strongly Interacting Quantum Systems out of Equilibrium

Author: Thierry Giamarchi

Publisher: Oxford University Press

Published: 2016-07-07

Total Pages: 464

ISBN-13: 0191080543

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Over the last decade new experimental tools and theoretical concepts are providing new insights into collective nonequilibrium behavior of quantum systems. The exquisite control provided by laser trapping and cooling techniques allows us to observe the behavior of condensed bose and degenerate Fermi gases under nonequilibrium drive or after `quenches' in which a Hamiltonian parameter is suddenly or slowly changed. On the solid state front, high intensity short-time pulses and fast (femtosecond) probes allow solids to be put into highly excited states and probed before relaxation and dissipation occur. Experimental developments are matched by progress in theoretical techniques ranging from exact solutions of strongly interacting nonequilibrium models to new approaches to nonequilibrium numerics. The summer school `Strongly interacting quantum systems out of equilibrium' held at the Les Houches School of Physics as its XCIX session was designed to summarize this progress, lay out the open questions and define directions for future work. This books collects the lecture notes of the main courses given in this summer school.

Fluctuations and Non-Equilibrium Phenomena in Strongly-Correlated Ultracold Atoms
Fluctuations and Non-Equilibrium Phenomena in Strongly-Correlated Ultracold Atoms

Author: Kazuma Nagao

Publisher: Springer Nature

Published: 2020-08-25

Total Pages: 126

ISBN-13: 9811571716

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This book discusses non-equilibrium quantum many-body dynamics, recently explored in an analog quantum simulator of strongly correlated ultracold atoms. The first part presents a field-theoretical analysis of the experimental observability of the Higgs amplitude mode that emerges as a relativistic collective excitation near a quantum phase transition of superfluid Bose gases in an optical lattice potential. The author presents the dynamical susceptibilities to external driving of the microscopic parameters, taking into account a leading-order perturbative correction from quantum and thermal fluctuations and shows clear signatures of the Higgs mode in these observables. This is the first result that strongly supports the stability of the Higgs mode in three-dimensional optical lattices even in the presence of a spatially inhomogeneous confinement potential and paves the way for desktop observations of the Higgs mode. In the second part, the author applies the semi-classical truncated-Wigner approximation (TWA) to far-from-equilibrium quantum dynamics. Specifically, he considers the recent experiments on quantum-quench dynamics in a Bose-Hubbard quantum simulator. A direct comparison shows remarkable agreement between the numerical results from TWA and the experimental data. This result clearly indicates the potential of such a semi-classical approach in reliably simulating many-body systems using classical computers. The book also includes several chapters providing comprehensive reviews of the recent studies on cold-atomic quantum simulation and various theoretical methods, including the Schwinger-boson approach in strongly correlated systems and the phase-space semi-classical method for far-from-equilibrium quantum dynamics. These chapters are highly recommended to students and young researchers who are interested in semi-classical approaches in non-equilibrium quantum dynamics.

Non-Equilibrium Nano-Physics
Non-Equilibrium Nano-Physics

Author: Jonas Fransson

Publisher: Springer Science & Business Media

Published: 2010-07-05

Total Pages: 230

ISBN-13: 9048192099

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The aim of this book is to present a formulation of the non-equilibrium physics in nanoscale systems in terms of many-body states and operators and, in addition, discuss a diagrammatic approach to Green functions expressed by many-body states. The intention is not to give an account of strongly correlated systems as such. Thus, the focus of this book ensues from the typical questions that arise when addressing nanoscale systems from a practical point of view, e.g. current-voltage asymmetries, negative differential conductance, spin-dependent tunneling. The focus is on nanoscale systems constituted of complexes of subsystems interacting with one another, under non-equilibrium conditions, in which the local properties of the subsystems are preferably being described in terms of its (many-body) eigenstates.

NON-EQUILIBRIUM DYNAMICS OF MANY-BODY QUANTUM SYSTEMS
NON-EQUILIBRIUM DYNAMICS OF MANY-BODY QUANTUM SYSTEMS

Author:

Publisher:

Published: 2013

Total Pages:

ISBN-13:

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Rapid progress in nanotechnology and naofabrication techniques has ushered in a new era of quantum transport experiments. This has in turn heightened the interest in theoretical understanding of nonequilibrium dynamics of strongly correlated quantum systems. This project has advanced the frontiers of understanding in this area along several fronts. For example, we showed that under certain conditions, quantum impurities out of equilibrium can be reformulated in terms of an effective equilibrium theory; this makes it possible to use the gamut of tools available for quantum systems in equilibrium. On a different front, we demonstrated that the elastic power of a transmitted microwave photon in circuit QED systems can exhibit a many-body Kondo resonance. We also showed that under many circumstances, bipartite fluctuations of particle number provide an effective tool for studying many-body physics--particularly the entanglement properties of a many-body system. This implies that it should be possible to measure many-body entanglement in relatively simple and tractable quantum systems. In addition, we studied charge relaxation in quantum RC circuits with a large number of conducting channels, and elucidated its relation to Kondo models in various regimes. We also extended our earlier work on the dynamics of driven and dissipative quantum spin-boson impurity systems, deriving a new formalism that makes it possible to compute the full spin density matrix and spin-spin correlation functions beyond the weak coupling limit. Finally, we provided a comprehensive analysis of the nonequilibrium transport near a quantum phase transition in the case of a spinless dissipative resonant-level model. This project supported the research of two Ph. D. students and two postdoctoral researchers, whose training will allow them to further advance the field in coming years.

Equilibrium and Non-equilibrium Statistical Mechanics
Equilibrium and Non-equilibrium Statistical Mechanics

Author: Carolyn M. Van Vliet

Publisher: World Scientific

Published: 2008

Total Pages: 987

ISBN-13: 9812704779

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This book encompasses our current understanding of the ensemble approach to many-body physics, phase transitions and other thermal phenomena, as well as the quantum foundations of linear response theory, kinetic equations and stochastic processes. It is destined to be a standard text for graduate students, but it will also serve the specialist-researcher in this fascinating field; some more elementary topics have been included in order to make the book self-contained.The historical methods of J Willard Gibbs and Ludwig Boltzmann, applied to the quantum description rather than phase space, are featured. The tools for computations in the microcanonical, canonical and grand-canonical ensembles are carefully developed and then applied to a variety of classical and standard quantum situations. After the language of second quantization has been introduced, strongly interacting systems, such as quantum liquids, superfluids and superconductivity, are treated in detail. For the connoisseur, there is a section on diagrammatic methods and applications.In the second part dealing with non-equilibrium processes, the emphasis is on the quantum foundations of Markovian behaviour and irreversibility via the Pauli-Van Hove master equation. Justifiable linear response expressions and the quantum-Boltzmann approach are discussed and applied to various condensed matter problems. From this basis the Onsager-Casimir relations are derived, together with the mesoscopic master equation, the Langevin equation and the Fokker-Planck truncation procedure. Brownian motion and modern stochastic problems such as fluctuations in optical signals and radiation fields briefly make the round.

Quantum Gases: Finite Temperature And Non-equilibrium Dynamics
Quantum Gases: Finite Temperature And Non-equilibrium Dynamics

Author: Nick P Proukakis

Publisher: World Scientific

Published: 2013-02-21

Total Pages: 579

ISBN-13: 1908979704

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The 1995 observation of Bose-Einstein condensation in dilute atomic vapours spawned the field of ultracold, degenerate quantum gases. Unprecedented developments in experimental design and precision control have led to quantum gases becoming the preferred playground for designer quantum many-body systems.This self-contained volume provides a broad overview of the principal theoretical techniques applied to non-equilibrium and finite temperature quantum gases. Covering Bose-Einstein condensates, degenerate Fermi gases, and the more recently realised exciton-polariton condensates, it fills a gap by linking between different methods with origins in condensed matter physics, quantum field theory, quantum optics, atomic physics, and statistical mechanics. Thematically organised chapters on different methodologies, contributed by key researchers using a unified notation, provide the first integrated view of the relative merits of individual approaches, aided by pertinent introductory chapters and the guidance of editorial notes.Both graduate students and established researchers wishing to understand the state of the art will greatly benefit from this comprehensive and up-to-date review of non-equilibrium and finite temperature techniques in the exciting and expanding field of quantum gases and liquids./a

Nonequilibrium Dynamics of Collective Excitations in Quantum Materials
Nonequilibrium Dynamics of Collective Excitations in Quantum Materials

Author: Edoardo Baldini

Publisher: Springer

Published: 2018-03-28

Total Pages: 360

ISBN-13: 3319774980

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This book studies the dynamics of fundamental collective excitations in quantum materials, focusing on the use of state-of-the-art ultrafast broadband optical spectroscopy. Collective behaviour in solids lies at the origin of several cooperative phenomena that can lead to profound transformations, instabilities and phase transitions. Revealing the dynamics of collective excitations is a topic of pivotal importance in contemporary condensed matter physics, as it provides information on the strength and spatial distribution of interactions and correlation. The experimental framework explored in this book relies on setting a material out-of-equilibrium by an ultrashort laser pulse and monitoring the photo-induced changes in its optical properties over a broad spectral region in the visible or deep-ultraviolet. Collective excitations (e.g. plasmons, excitons, phonons...) emerge either in the frequency domain as spectral features across the probed range, or in the time domain as coherent modes triggered by the pump pulse. Mapping the temporal evolution of these collective excitations provides access to the hierarchy of low-energy phenomena occurring in the solid during its path towards thermodynamic equilibrium. This methodology is used to investigate a number of strongly interacting and correlated materials with an increasing degree of internal complexity beyond conventional band theory.