Correlated Quantum States in Rotationally Controlled Double Layers of 2D Materials
Abstract
We propose an experimental investigation of interaction-driven exotic quantum states in rotationally controlled double layers of twodimensional (2D) materials, consisting of combinations of graphene, transition metal dichalcogenide layers, and dielectrics. The emphasis of the study will be on paired electron-hole states (indirect excitons) in independently contacted double layers, and equilibrium exciton condensation at zero magnetic field. This study has the potential to resolve a long-standing quest for interaction-driven dipolar superfluidity in double layers at zero magnetic field, with implications for the pairing mechanism and superconductivity in twodimensions in general. The specific systems to be investigated consist of (1) rotationally aligned graphene layers separated by a single crystal tunnel barrier with independent contacts to the two layers, (2) double moirŽ patterns consisting of two magic-angle twisted bilayer graphene separated by a tunnel barrier, and (3) double moirŽ patterns in transition metal dichalcogenide van der Waals heterostructures. Our objectives are to: 1. Realize rotationally aligned double bilayer graphene separated a single crystal tunnel barrier, such as hexagonal boron-nitride (hBN) or tungsten diselenide (WSe2), and using graphene as top and bottom gate, and probe the tunneling characteristics as a function of temperature and in-plane magnetic field, with an emphasis on the tunneling conductance when the layers are populated with equal and opposite carrier densities. 2. Identify regimes where the inter-layer conductance is significantly enhanced at low temperatures compared to single particle calculations, and assess is Josephson junction behavior can be observed in the tunneling current-voltage characteristics. 3. Design and realize double moirŽ patterns, consisting of two magic-angle twisted bilayer graphene with independent contacts to each moirŽ pattern, and probe the interlayer tunneling and Coulomb drag in the double moirŽ pattern. The goal of this task is to identify if paired states emerge when the flat bands in each magic-angle twisted bilayer graphene have complementary filling factors. 4. Design and implement double moirŽ patterns in transition metal dichalcogenide-based vdW heterostructures, and probe the transport characteristics with an emphasis on paired states at fractional moirŽ band filling factors, but at total integer moirŽ band filling factor, such as half-filled moirŽ band in each layer. We will use the cut-and-stack technique to realize either rotationally aligned double layers, or double moirŽ patterns. The proposed research leverages novel experimental techniques developed by the PIÕs group, which include techniques for the realization of rotationally controlled van der Waals heterostructures, moirŽ patterns in twisted bilayer and twisted double bilayer graphene, twisted WSe2 bilayers, low temperature quantum Hall effect studies in WSe2 and MoSe2 carrier systems, and the realization of rotationally controlled double layers in TMD- and graphene-based heterostructures. The proposed effort has the potential to significantly advance in the study of equilibrium exciton condensates, and other correlated states. The proposed effort is also expected to further the development of sample fabrication techniques, and provide spin-off potential applications to military technology in THz generation, and cryogenic computing.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 17, 2022
- Source ID
- W911NF2210160
Entities
People
- Emanuel Tutuc
Organizations
- Army Contracting Command
- United States Army
- University of Texas at Austin