[PAST EVENT] Physics Colloquium - Daniel Rhodes
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Daniel Rhodes, Columbia University, Title of talk: Disorder and Superconductivity in 2D TMD Heterostructures
Abstract: Two dimensional transition metal dichalcogenides (TMD) interest due to their novel optical and electronic properties, and their potential for application. However, observations of the emergent phenomena in these materials is limited by scattering and nonradiative recombination processes due to a large density of defects and disorder at the interface. In this work, using a combination of scanning tunneling microscopy (STM) and scanning transmission electron microscopy (STEM), we characterize the atomic and electronic nature of intrinsic point defects in single crystal TMDs. We demonstrate that these defects can be reduced by almost three orders of magnitude (1013/cm2 to 5 x 1010/cm2) through a self-flux growth method. This method of growth can be applied across a variety of TMDs and we further utilize this method to grow the superconducting TMD?MoTe2. In the bulk, MoTe2 is a type II Weyl semimetal with a superconducting transition temperature (Tc) of 120 mK. I will show that in the clean limit, the superconducting transition temperature is enhanced by a factor of 60x in monolayer Td-MoTe2, while still retaining a low carrier density (~1013/cm2). Reflecting the low carrier density, the critical temperature, magnetic field, and current density are all tunable by an applied gate voltage. Furthermore, the temperature dependence of the in-plane upper critical field is distinct from that of 2H-TMDs, consistent with a complex spin texture predicted by ab initio theory.