Dynamics, Thermodynamics and Spin Transport in Random Quantum Spin Chains

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9971541 Yang This award is comprised of a number of theoretical projects that are aimed at enhancing our understanding of the long-distance, low-energy properties of various random quantum magnetic systems, especially random spin chains. The motivation for these theoretical studies comes from both the extensive experimental activity with these types of systems, and the general interest in understanding the physics of quantum many-body systems with strong interaction/correlation and strong disorder.In general, strong interaction and disorder in many-body systems cannot be treated using standard perturbation theory, especially when the dimensionality of the system is low. Random quantum spin chains are typical examples of such systems. Powerful nonperturbative theoretical tools have been developed recently to study quantum spin chains, taking advantage of their one-dimensional nature. These tools include mapping onto effective quantum field theories, bosonization, real space renormalization group, etc.In the projects studied here, one uses and extends these tools to uncover important new information about the physical properties of these systems, including: the spin dynamics and transport properties of various stable phases supported by random spin chains; whether there exist new stable phases in random quantum spin chains that have not been studied before, when more general couplings (other than those studied thus far) among spins are allowed; the effects of transverse couplings between the chains on the physical properties; the effects of disorder generated by dynamical degrees of freedom in the system, etc. Attempts will also be made to develop new theoretical tools to study these systems, such as describing spin chains using field theories in terms of some novel non-local order parameters.Progress made on these projects is expected not only to deepen our understandings of the physics of various random quantum systems, but also to shed light on the properties of strongly interacting many-body systems in general. %%%This award is comprised of a number of theoretical projects that are aimed at enhancing our understanding of the long-distance, low-energy properties of various random quantum magnetic systems, especially random spin chains. The motivation for these theoretical studies comes from both the extensive experimental activity with these types of systems, and the general interest in understanding the physics of quantum many-body systems with strong interaction/correlation and strong disorder.Progress made on these projects is expected not only to deepen our understandings of the physics of various random quantum systems, but also to shed light on the properties of strongly interacting many-body systems in general.***