September 2021
Abstracts of the QSIT Lunch Seminar, Thursday, September 2, 2021
Engineering Dynamical Tunneling in Quantum Gas Coupled to a Cavity
Rodrigo Rosa-Medina - Quantum Optics Group (Esslinger group), ETH Zurich
In our experiment, we couple a Bose-Einstein condensate (BEC) to a high-finesse optical resonator to explore different scenarios of many-body cavity QED. This complex light-matter system offers unique possibilities to simulate solid-state Hamiltonians and realize out-of-equilibrium scenarios beyond conventional materials. In particular, the photons leaking out of the cavity allow real-time access to the dynamics and, at the same time, render the system intrinsically non-Hermitian [1].
In this talk, I will report on the experimental realization of dynamical tunneling in a synthetic lattice in momentum space [2]. Our implementation is based on a spinor BEC coupled to the cavity and driven by two transverse laser fields. This gives rise to collective Raman scattering with the photons imparting discrete momenta on the BEC, which we interpret as cavity-assisted tunneling in a momentum grid. As the emerging cavity field depends on the spin and density configuration of the atoms, the tunneling rate is not externally determined but rather evolves dynamically with the atomic state. The photon field inducing the tunneling process is subject to cavity dissipation, resulting in effective directional currents in a non-Hermitian setting. By leveraging on the cavity leakage, we gain non-destructive, real-time access to the emerging currents, which is often challenging in cold-atom experiments.
Our results offer prospects to explore dynamical currents in strongly-correlated settings and to advance towards the simulation of lattice gauge theories.
[1] Ferri, F., Rosa-Medina, R., Finger, F., Dogra, N., Soriente, M., Zilberberg, O., Donner, T., Esslinger, T. (2021). arXiv:2104.12782.
[2] Rosa-Medina, R., Ferri, F., Finger, F., Dogra, N., Kroeger, K., Lin, R., Chitra, R., Donner, T., Esslinger, T. (2021). arXiv:2108.11888
Tunable quantum confinement of neutral excitons using electric fields and exciton-charge interactions
Deepankur Thureja - Quantum Photonics Group (Imamoglu group), ETH Zurich
The realization of fully tunable quantum emitters in solid state systems has been an outstanding goal of optoelectronics and quantum photonics. In this talk I will discuss our recent experimental results demonstrating quantum confinement of neutral excitons in monolayer transition metal dichalcogenides with full electrical control [1]. We show that excitons can be quantum confined at few nanometer length scales, through the dc Stark effect induced by strong in-plane electric fields in the insulating region of a p-i-n diode. Furthermore, we find a new confinement mechanism that exploits the repulsive interactions of neutral excitons in the i-region with the surrounding Fermi sea of itinerant charges in the n- and p-doped regions.
Our optical experiments reveal the quantization of excitonic motion into discrete states, which is an unambiguous signature of quantum confinement. An important feature of our approach is that it achieves quantum confinement without relying on lithographic patterning at nanoscopic scales. Such electrically tunable quantum confined excitons may provide a scalable platform for arrays of identical single photon sources and constitute building blocks of strongly correlated photonic many-body systems.
[1] D. Thureja et. al, “Electrically controlled quantum confinement of excitons in 2D semiconductors”, arXiv:2102.08989.