Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session W37: Strongly correlation physics in transition metal dichalcogenidesInvited
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Sponsoring Units: DCMP Chair: Eun-Ah Kim, Cornell University Room: Room 233 |
Thursday, March 9, 2023 3:00PM - 3:36PM |
W37.00001: Strongly correlated excitons in atomic double layers Invited Speaker: Jie Shan Excitonic insulators (EIs) occur in a small-gap semiconductor when the electron-hole binding energy exceeds the charge bandgap. They can also occur in small band overlap semimetals. The ground state exciton population is determined by balancing the negative exciton formation energy against the mean exciton-exciton repulsion energy. EIs provide a solid-state platform for quantum many-boson physics. Although the concept has been understood for decades, establishing distinct experimental signatures of the realization of EIs has remained challenging. In this talk, I discuss a recent experiment in which we establish electrical control of the chemical potential of interlayer excitons in atomic double layers of semiconducting transition metal dichalcogenide and probe the thermodynamic properties of exciton fluids by capacitance measurements. I will also discuss the possibility of creating exciton fluids in a lattice to realize the Bose-Hubbard model. |
Thursday, March 9, 2023 3:36PM - 4:12PM |
W37.00002: Tunable Correlations in Twisted WSe2 Bilayers Invited Speaker: Abhay N Pasupathy Twisted WSe2 realizes a triangular lattice moiré-patterned semiconductor with a bandwidth set by the twist angle. Using electrostatic gates, it is possible to study the ground state of this material as a function of carrier doping and applied electric field using transport measurements. The applied electric field is an especially important parameter in these experiments, that effectively allows us to tune the bandwidth of the system. I will describe a series of experiments where we tune electric field, doping and twist angle to probe the emergent quantum states in this material. I will discuss the emergence of insulating states driven by correlations at half-filling of the lowest moiré subband; the melting of this insulator by doping and electric field; and the emergence of magnetic metallic states in the weakly-correlated region of the phase diagram. |
Thursday, March 9, 2023 4:12PM - 4:48PM |
W37.00003: Quantum phases of transition metal dichalcogenide moire systems Invited Speaker: Yiqing Zhou Moire systems provide a rich platform for studies of strong correlation physics. Recent experiments on heterobilayer transition metal dichalcogenide moire systems are exciting in that they manifest a relatively simple model system of an extended Hubbard model on a triangular lattice. Inspired by the prospect of the hetero-transition metal dichalcogenide moire system’s potential as a solid-state-based quantum simulator, we explore the extended Hubbard model on the triangular lattice using the density matrix renormalization group[1]. We explore the two-dimensional phase space spanned by the key tuning parameters in the extended Hubbard model, namely, the kinetic energy and the further-range Coulomb interaction strengths. We find competition between Fermi fluid, chiral spin liquid, spin density wave, and charge order. In particular, our finding of the optimal further-range interaction for the chiral correlation presents a tantalizing possibility. |
Thursday, March 9, 2023 4:48PM - 5:24PM |
W37.00004: Single-electron transistor microscopy of correlated states in semiconductor moiré lattices Invited Speaker: Ben Feldman When two materials with similar lattice constants are stacked with a small interlayer twist, a long-wavelength moiré superlattice develops. This can lead to flat electronic bands which host a variety of interaction-driven phases. Moiré systems composed from semiconducting transition metal dichalcogenides (TMDs) represent an especially flexible platform because the ground states can be tuned by adjusting constituent materials, twist angle, and applied electromagnetic fields. In this talk, I will describe local electronic compressibility measurements conducted with a scanning single-electron transistor that reveal a rich phase diagram of correlated states in twisted TMD systems. We elucidate the spin, valley, and real-space character of the ground states and identify novel excitations. In addition, we demonstrate control over which states are favored by adjusting carrier density and applied electric/magnetic fields. I will discuss how our thermodynamic measurements provide insight into how electronic interactions combine with the underlying nature of the moiré bands to produce multiple distinct regimes of physical behavior. |
Thursday, March 9, 2023 5:24PM - 6:00PM |
W37.00005: Semiconductor Homobilayer Moiré Materials: The Difference Between K and Gamma Invited Speaker: Allan H MacDonald Moiré materials are artificial two-dimensional crystals with lattice constants that are large enough to enable large gate-controlled changes in the number of electrons per effective atom. Because their bands can have non-trivial topology related to their k-dependent sublattice eigenspinors, and have widths that are conveniently tunable, they are an ideal laboratory to assess our understanding of key issues in the theory of condensed matter. Among these are the interplay between long-range exchange interactions and lattice scale correlations and the importance of non-trivial band topology in controlling the appearance of magnetism and superconductivity. My talk will focus on understanding the qualitative differences between the electronic properties of moiré materials hosted in the valence bands of K and Gamma valley transition metal dichalcogenide homobilayers. I will specifically discuss the role of long-range Coulomb interactions, design rules for spin and orbital magnetism in both metallic and insulating states, and the absence of superconductivity (so far) in both cases. |
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