Geva Arwas

Chaos and two-level dynamics of the Atomtronic Quantum Interference Device

We study the atomtronic quantum interference device employing a semiclassical perspective. We consider an M site ring that is described by the Bose–Hubbard Hamiltonian. Coherent Rabi oscillations in the flow of the current are feasible, with an enhanced frequency due to chaos-assisted tunneling. We highlight the consequences of introducing a weak-link into the circuit. In the latter context we clarify the phase–space considerations that are involved in setting up an effective systems plus bath description in terms of Josephson–Caldeira–Leggett Hamiltonian.

Superfluidity and Chaos in low dimensional circuits

The hallmark of superfluidity is the appearance of “vortex states” carrying a quantized metastable circulating current. Considering a unidirectional flow of particles in a ring, at first it appears that any amount of scattering will randomize the velocity, as in the Drude model, and eventually the ergodic steady state will be characterized by a vanishingly small fluctuating current. However, Landau and followers have shown that this is not always the case. If elementary excitations (e.g. phonons) have higher velocity than that of the flow, simple kinematic considerations imply metastability of the vortex state: the energy of the motion cannot dissipate into phonons. On the other hand if this Landau criterion is violated the circulating current can decay. Below we show that the standard Landau and Bogoliubov superfluidity criteria fail in low-dimensional circuits. Proper determination of the superfluidity regime-diagram must account for the crucial role of chaos, an ingredient missing from the conventional stability analysis. Accordingly, we find novel types of superfluidity, associated with irregular or chaotic or breathing vortex states.

Triangular Bose-Hubbard trimer as a minimal model for a superfluid circuit

The triangular Bose-Hubbard trimer is topologically the minimal model for a BEC superfluid circuit. As a dynamical system of two coupled freedoms it has mixed phase-space with chaotic dynamics. We employ a semiclassical perspective to study triangular trimer physics beyond the conventional picture of the superfluid-to-insulator transition. From the analysis of the Peierls-Nabarro energy landscape, we deduce the various regimes in the

Superfluidity in Bose-Hubbard circuits

(Omega,u)

Chaos, metastability and ergodicity in Bose-Hubbard superfluid circuits

parameter-space, where

Resonant persistent currents for ultracold bosons on a lattice ring

u

Multiple-path transport in quantum networks

is the interaction, and

Monodromy and chaos for condensed bosons in optical lattices

Omega

Superfluidity of Bose-Hubbard circuits: beyond the traditional paradigm

is the superfluid rotation-velocity. We thus characterize the superfluid-stability and chaoticity of the many-body eigenstates throughout the Hilbert space.

Superfluidity and Chaos

A semiclassical theory is provided for the metastability regime-diagram of atomtronic superfluid circuits. Such circuits typically exhibit high-dimensional chaos; and non-linear resonances that couple the Bogoliubov excitations manifest themselves. Contrary to the expectation these resonances do not originate from the familiar Beliaev and Landau damping terms. Rather, they are described by a variant of the Cherry Hamiltonian of celestial mechanics. Consequently we study the induced decay process, and its dependence on the number of sites and of condensed particles.