Non-equilibrium dynamics of atomic gases in optical cavities
Professor Nigel Cooper, University of Cambridge, UK
A novel feature of cold gases is the possibility to couple the motional dynamics of a quantum many body system to (one or more) quantized bosonic modes, describing the light fields in optical cavities. Such matter-light coupled systems show interesting forms of collective dynamics. They are subject to dissipation through fluctuations/damping of the cavity mode. Cooper will present theoretical results that demonstrate examples of these novel collective dynamics, both in uniform and disordered settings, focusing on the question of whether or not the dissipative dynamics drive the system to a unique steady state.
Optically driven strongly correlated quantum systems
Professor Dieter Jaksch, University of Oxford, UK
Recent experiments [1,2] indicate that selective optical driving of phonons may generate or enhance ordered phases in strongly correlated quantum materials. In his talk Jaksch will discuss quantum optically inspired models that may help explain and engineer such phenomena. Specifically, Jaksch will consider a driven fermionic Hubbard model in the strongly correlated limit where the onsite interaction dominates over the kinetic energy . The driving is modelled as an alternating periodic modulation of the lattice site energy offsets. He will demonstrate how this modulation suppresses tunnelling and induces exchange interactions. The combination of these effects changes the nature of the system into an attractive Luttinger liquid and leads to enhanced fermion pairing in one spatial dimension. Jaksch will present results at zero and finite temperatures and discuss the prospect of observing driven out-of-equilibrium superconductivity in this model system.
- D. Fausti, R.I. Tobey, N. Dean, S. Kaiser, A. Dienst, M.C. Hoffmann, S. Pyon, T. Takayama, H. Takagi, and A. Cavalleri, Light-Induced Superconductivity in a Stripe-Ordered Cuprate. Science 331, 189 (2011).
- M. Mitrano, A. Cantaluppi, D. Nicoletti, S. Kaiser, A. Perucchi, S. Lupi, P. Di Pietro, D. Pontiroli, M. Ricco, S.R. Clark, D. Jaksch and A. Cavalleri, Possible light-induced superconductivity in K3C60 at high temperature. Nature 530, 461-464 (2016).
- J. Coulthard, S.R. Clark, S. Al-Assam, A. Cavalleri and D. Jaksch, Enhancement of super-exchange pairing in the periodically-driven Hubbard model, arXiv:1608.03964 (2016).
Signature of non-ergodicity in low-lying excitations of disordered many-particle systems
Professor Richard Berkovits, Bar-Ilan University, Israel
The statistical properties of the entanglement spectrum of a disordered many-particle system are studied, in order to identify the localized to extended transition as function of interaction strength and excitation energy expected from the many-body localization transition. In his talk, Berkovits shows that an indication of such a transition is indeed observed, and some of the features may be interpreted as a signature of non-ergodic behaviour.
Engineered dissipation and out-of-equilibrium many-body dynamics with cold atoms
Professor Andrew Daley, University of Strathclyde, UK
The time-dependent microscopic control available in experiments with systems of ultracold atoms has opened new opportunities to explore many-body dynamics, addressing fundamental questions both in and out of equilibrium. This control can also be extended beyond the coherent dynamics of the system, as in typical experimental regimes the dominant mechanisms for dissipation can both be described microscopically from first principles, and can be controlled with external fields. Such control originates in the separation of timescales for coupling to a reservoir and for the relaxation of the reservoir, which is typical in quantum optics. This allows us to calculate and explore the effect of dissipation on the many-body dynamics, including on the ergodicity of dynamics after a parameter quench. We can also go further, especially in engineering dissipative processes that will drive the system into specific interacting many-body states. Daley will discuss his group’s recent work in this direction, especially looking at the microscopic description of dissipation for cold atoms in optical lattices in the presence of light scattering or with the addition of a second species that acts as a reservoir, and describe applications towards the generation of strongly correlated many-body states, and the investigation of out-of-equilibrium dynamics (including in systems exhibiting many-body-localisation).