Dynamical Gauge Effects and Holographic Scaling of Non-Equilibrium Motion in a Disordered and Dissipative Atomic Gas

Open Access
Zhao, Jianshi
Graduate Program:
Doctor of Philosophy
Document Type:
Date of Defense:
January 30, 2017
Committee Members:
  • Nathan Gemelke, Dissertation Advisor
  • Nathan Gemelke, Committee Chair
  • David Weiss, Committee Member
  • Jainendra Jain, Committee Member
  • Venkatraman Gopalan, Outside Member
  • Gauge Field
  • Laser Cooling
  • Disordered Potential
  • Raman Sideband Cooling
  • Fractional Quantum Hall
  • Non-equilibrium
  • Optial Lattice
In this thesis, we describe both an experimental implementation and a theoretical investigation of gauge field effects in cold atom systems. The experimental part focuses on the motion of atoms in a disordered potential with dissipation. The atomic system under consideration utilizes a generalization of a dark state cooling mechanism, known as Ramman sideband cooling. By coupling near-resonant laser modes, we create an open system which exhibits a non-equilibrium phase transition between two steady-state behaviors, and shows scale-invariant behavior near the transition. This behavior is loosely analogous to dynamical gauge effects in quantum chromodynamics, and can be mapped onto generalized open problems in theoretical understanding of quantized non-Abelian gauge theories. Additionally, the scaling behavior can be understood from the geometric structure of the gauge potential and linked to a measure of information in the local disordered potential, reflecting an underlying holographic principle. As an extension toward developing fractional quantum Hall (FQH) systems, we consider an experimental strategy of creating many FQH samples along a chain of lattice sites, and coupling them together via tunneling. We calculate a mean-field phase diagram and derive an effective field theory to describe this system and find that such a system support novel insulator and superfluid states. Close to the centrifugal limit with small tunneling strength, 1/2-Laughlin states with N atoms are localized on each lattice site, analogous to Mott-Insulator state. As the tunneling strength increases, the system transitions from the Laughlin-insulator states to superfluid states, whose order parameter reflects the insulator states through momentum and atom number conservation. The transport properties near the phase transition reveal the fractional 'charge' nature of the insulator states, in such that the effective mass of the tunneling quasi-particle is fractionalized. We demonstrate an experimentally feasible pathway to a state describable as a Mott-insulator of 1/2-Laughlin states, and also interrogate the coherence properties of the superfluid phase.