Itinerant ferromagnetism in transition metal dichalcogenides moir\'e superlattices

Moir\'e materials are artificial crystals formed at van der Waals heterojunctions that have emerged as a highly tunable platform to realize much of the rich quantum physics of electrons in atomic scale solids, also providing opportunities to discover new quantum phases of matter. Here we use finite-size exact diagonalization methods to explore the physics of single-band itinerant electron ferromagnetism in semiconductor moir\'e materials. We predict where ferromagnetism is likely to occur in triangular-lattice moir\'e systems, and where it is likely to yield the highest Curie temperatures.Comment: 15 pages, 14 figure

Gate-tunable heavy fermion quantum criticality in a moiré Kondo lattice

We propose a realization of Kondo-lattice physics in moiré superlattices at the interface between a WX2 homobilayer and MoX2 monolayer (where X=S,Se). Under appropriate gating conditions, the interface-WX2-layer forms a triangular lattice of local moments that couple to itinerant electrons in the other WX2-layer via a gate-tunable Kondo exchange interaction. Using a parton mean-field approach we identify a range of twist-angles which support a gate-tuned quantum phase transition between a heavy-fermion liquid with large anomalous Hall conductance and a fractionalized chiral spin-liquid coexisting with a light Fermi liquid, and describe experimental signatures to distinguish among competing theoretical scenarios.AK and AP were supported by the National Science Foundation through the Center for Dynamics and Control of Materials: an NSF MR- SEC under Cooperative Agreement No. DMR-1720595. NCH and AHM were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, un- der Award # DE-SC0019481. AP acknowledges support from the Alfred P. Sloan Foundation through a Sloan Re- search Fellowship. This research was undertaken thanks, in part, to funding from the Max Planck-UBC-UTokyo Center for Quantum Materials and the Canada First Re- search Excellence Fund, Quantum Materials and Future Technologies Program.Center for Dynamics and Control of Material

Experimental Gaussian Boson Sampling

Gaussian Boson sampling (GBS) provides a highly efficient approach to make use of squeezed states from parametric down-conversion to solve a classically hard-to-solve sampling problem. The GBS protocol not only significantly enhances the photon generation probability, compared to standard boson sampling with single photon Fock states, but also links to potential applications such as dense subgraph problems and molecular vibronic spectra. Here, we report the first experimental demonstration of GBS using squeezed-state sources with simultaneously high photon indistinguishability and collection efficiency. We implement and validate 3-, 4- and 5-photon GBS with high sampling rates of 832 kHz, 163 kHz and 23 kHz, respectively, which is more than 4.4, 12.0, and 29.5 times faster than the previous experiments. Further, we observe a quantum speed-up on a NP-hard optimization problem when comparing with simulated thermal sampler and uniform sampler.Comment: 12 pages, 4 figures, published online on 2nd April 201