Coherent dynamics and topological phases with ultracold atoms

Christof Weitenberg

Dong-Ling Deng, Sheng-Tao Wang, Kai Sun +1 more

Ruosong Mao, Xingqi Xu, Jiefei Wang +5 more

Ultracold atoms provide a flexible platform for simulating topological phases. However, they are intrinsically prone to thermal noise, which can overwhelm topological response and hamper promised applications. On the other hand, topological invariants can be reconstructed from the energy spectra of particles subjected to a static force, based on the polarization relation between Wannier-Stark ladders and Zak phases. Such spectroscopic methods circumvent the obstacle to measuring topological invariants in thermal atoms. Here we reconstruct Zak phases from the anti-crossing between Wannier-Stark ladders in room-temperature superradiance lattices. Without dynamical manipulation routinely needed in ultracold atoms, we evaluate Zak phases directly from the absorption spectra. The thermal atomic motion, an essential source of noise in cold atoms, plays a key role in extracting Zak phases. Our approach paves the way of measuring topological invariants and developing their applications in room-temperature atoms.

Alexandru Petrescu

We propose theoretical models that support topological phases and which are relevant to current experiments on lattices hosting photonic modes or ultracold atoms. In the first part of this thesis, we introduce a topological phase on a Kagom ́e lattice whose degrees of freedom are photons. In that context, we discuss two protocols to access the local Berry curvature and the Chern number of Bloch bands from semiclassical dynamics of wavepackets. Secondly, we obtain the phase diagram for bosons at unit filling with repulsive on–site interactions whose kinetic term corresponds to a Chern insulator defined on the honeycomb lattice. In the second part, we turn to recently realized quasi one–dimensional lattices, and un- cover their phase diagrams, comprising low–dimensional Meissner phases, chiral Mott insulating phases as well as abelian fractional quantum Hall states.

M. Ueda

Roberto Onofrio, Luca Salasnich