Interaction effects and superconductivity signatures in twisted double-bilayer WSe2.
Nanoscale horizons 5:9 (2020) 1309-1316
Abstract:
Twisted bilayer graphene provides a new two-dimensional platform for studying electron interaction phenomena and flat band properties such as correlated insulator transition, superconductivity and ferromagnetism at certain magic angles. Here, we present experimental characterization of interaction effects and superconductivity signatures in p-type twisted double-bilayer WSe2. Enhanced interlayer interactions are observed when the twist angle decreases to a few degrees as reflected by the high-order satellites in the electron diffraction patterns taken from the reconstructed domains from a conventional moiré superlattice. In contrast to twisted bilayer graphene, there is no specific magic angle for twisted WSe2. Flat band properties are observable at twist angles ranging from 1 to 4 degrees. Our work has facilitated future study in the area of flat band related properties in twisted transition metal dichalcogenide layered structures.Kerr effect anomaly in magnetic topological insulator superlattices
Nanotechnology IOP Publishing 31:43 (2020) 434001
Abstract:
We report the magneto-optical Kerr effect (MOKE) study of magnetic topological insulator superlattice films with alternating transition-metal and rare-earth doping. We observe an unexpected hump in the MOKE hysteresis loops upon magnetization reversal at low temperatures, reminiscent of the topological Hall effect(THE) reported in transport measurements. The THE is commonly associated with the existence of magnetic skyrmions, i.e., chiral spin textures originating from topological defects in real space. Here, the observation of the effect is tied to ferromagnetic ordering in the rare-earth-doped layers of the superlattice. Our study may provide a new approach for the non-invasive optical investigation of skyrmions in magnetic films, complementary to electrical transport measurements, where the topological Hall signal is often the only hint of non-trivial magnetization patterns.Topological Lifshitz transition of the intersurface Fermi-arc loop in NbIrTe4
Physical Review B American Physical Society (APS) 102:8 (2020) 085126
Angle-Resolved Photoemission Spectroscopy Study of Topological Quantum Materials
Chapter in , Annual Reviews 50:1 (2020) 131-153
Electronic structure of the Si-containing topological Dirac semimetal CaAl2Si2
Physical Review B American Physical Society (APS) 102:4 (2020) 045106