Speaker: Kin Fai Mak - Cornell University
Time: January 09, 2020 :: 2:00PM - 3:00PM
The Hubbard model, first formulated by physicist John Hubbard in the 1960s, is a simple theoretical model of interacting quantum particles in a lattice. The model is thought to capture the essential physics of high-temperature superconductors, magnetic insulators, and other complex emergent quantum many-body ground states. Although the Hubbard model is greatly simplified as a representation of most real materials, it has nevertheless proved difficult to solve accurately except in the one-dimensional case. Physical realizations of the Hubbard model in two or three dimensions, which can act as quantum simulators, therefore have a vital role to play in solving the strong-correlation puzzle. In this talk, I will discuss a recent experimental realization of the two-dimensional triangular lattice Hubbard model in angle-aligned WSe2/WS2 bilayers, which form moiré superlattices because of the difference in lattice constant between the two 2D materials. We obtain a quantum phase diagram of the two-dimensional triangular lattice Hubbard model near the half filling by probing both the charge and magnetic order of the system. Implications for future studies will also be discussed.
Kin Fai Mak received his PhD in physics from Columbia University. He is now an associate professor of physics and of applied & engineering physics at Cornell University. His research group explores new physical phenomena in atomically thin materials and their heterostructures. He studies a wide range of materials with very different properties, which include semiconductors, superconductors and magnets etc, and fabricates heteostructures, and devices based on this material platform. To explore new phenomena, he also develops new measurement and imaging techniques suitable for specific problems on hand. Recent research topics in his group include exciton condensation in double layer van der Waals’ heterostructures, strong correlation physics in moire superlattices, 2D magnetism, 2D superconductivity and topological transport phenomena.