Quantum Group Meeting: 2D Plus : Novel Approach to Synthesizing Two-Dimensional Materials, Yanyu Jia [Wu group]

Date
Feb 16, 2023, 12:00 pm1:30 pm
Location
J323

Details

Event Description

Title: 2D Plus : Novel Approach to Synthesizing Two-Dimensional Materials

Abstract: Fick’s laws of diffusion, which state that the diffusion flux is proportional to the concentration gradient, govern mass transport processes widely observed in physical, chemical, and biological systems. In solids, mass transport typically occurs slowly via substitutional or interstitial atomic migration, following Fick’s laws. Anomalous transport, i.e., passive mass propagation that disobeys Fick’s laws, is rare in crystals. Here we report the surprising observation of a rapid, long-distance, non-Fickian transport of a uniform layer of atomically thin palladium (Pd) on a monolayer crystal of tungsten ditelluride (WTe2), at temperatures above 190 oC, well below the known melting points of all materials involved. This process occurs when the monolayer crystal is either free-standing or fully encapsulated in a van der Waals (vdW) stack. Consequently, we establish a new route, likely generalizable, for synthesizing two-dimensional (2D) materials in a confined 2D space, distinct from conventional vapor deposition or epitaxial approaches. We realize a controlled synthesis of a new 2D crystalline material, Pd7WTe2, which was not known to exist previously. Transport studies confirm that it is a superconductor with a transition temperature near 0.5 K. Our study reveals exciting possibilities of non-Fickian mass transport on 2D crystals and demonstrates a furnace-free, on-chip approach for exploring controlled chemistry on a monolayer.