A. J. Campbell, M. Brotons-Gisbert, H. Baek, V. Vitale, T. Taniguchi, K. Watanabe, J. Lischner, and B. D. Gerardot, Strongly correlated electronic states in a Fermi sea spatially pinned by a MoSe2/WSe2 moiré superlattice, http://arxiv.org/abs/2202.08879



Two-dimensional moiré materials provide a highly tunable platform to investigate strongly correlated electronic states. Such emergent many-body phenomena can be optically probed in moiré systems created by stacking two layers of transition metal dichalcogenide semiconductors: optically injected excitons can interact with itinerant carriers occupying narrow moiré bands to form exciton-polarons sensitive to strong correlations. Here, we investigate the many-body interactions between excitons and a Fermi sea that is spatially pinned by the moiré superlattice of a molybdenum diselenide (MoSe2) / tungsten diselenide (WSe2) twisted hetero-bilayer. At a multitude of fractional fillings of the moiré lattice, we observe ordering of both electrons and holes into stable correlated electronic states. Magneto-optical measurements reveal extraordinary Zeeman splittings of the exciton-polarons due to exchange interactions between holes in the correlated phases, with a maximum close to the correlated state at one hole per site. The temperature dependence of the Zeeman splitting reveals antiferromagnetic ordering of the correlated holes across a wide range of fractional fillings. Our results illustrate the nature of excitons interacting with a spatially pinned Fermi sea and provide robust evidence for strongly correlated electronic states in MoSe2/WSe2 hetero-bilayers, unveiling the rich potential of this platform for investigations of Fermi-Hubbard and Bose-Hubbard physics.

M. Turunen, M. Brotons-Gisbert, Y. Dai, Y. Wang, E. Scerri, C. Bonato, K. D. Jöns, Z. Sun, and B. D. Gerardot, Quantum photonics with layered 2D materials, https://www.nature.com/articles/s42254-021-00408-0


Solid-state quantum devices use quantum entanglement for various quantum technologies, such as quantum computation, encryption, communication and sensing. Solid-state platforms for quantum photonics include single molecules, individual defects in crystals and semiconductor quantum dots, which have enabled coherent quantum control and readout of single spins (stationary quantum bits) and generation of indistinguishable single photons (flying quantum bits) and their entanglement. In the past 6 years, new opportunities have arisen with the emergence of 2D layered van der Waals materials. These materials offer a highly attractive quantum photonic platform that provides maximum versatility, ultrahigh light–matter interaction efficiency and novel opportunities to engineer quantum states. In this Review, we discuss the recent progress in the field of 2D layered materials towards coherent quantum photonic devices. We focus on the current state of the art and summarize the fundamental properties and current challenges. Finally, we provide an outlook for future prospects in this rapidly advancing field.

Z. X. Koong, M. Cygorek, E. Scerri, T. S. Santana, S. I. Park, J. D. Song, E. M. Gauger, and B. D. Gerardot, Coherence in Cooperative Photon Emission from Indistinguishable Quantum Emitters,    https://www.science.org/doi/10.1126/sciadv.abm8171 


Photon-mediated interactions between atoms can arise via coupling to a common electromagnetic mode or by quantum interference. Here, we probe the role of coherence in cooperative emission arising from two distant but indistinguishable solid-state emitters because of path erasure. The primary signature of cooperative emission, the emergence of “bunching” at zero delay in an intensity correlation experiment, is used to characterize the indistinguishability of the emitters, their dephasing, and the degree of correlation in the joint system that can be coherently controlled. In a stark departure from a pair of uncorrelated emitters, in Hong-Ou-Mandel–type interference measurements, we observe photon statistics from a pair of indistinguishable emitters resembling that of a weak coherent state from an attenuated laser. Our experiments establish techniques to control and characterize cooperative behavior between matter qubits using the full quantum optics toolbox, a key step toward realizing large-scale quantum photonic networks.