Combined momentum- and real-space photoelectric probes of dimensionality-tuned Weyl semimetals

Summary

The library of two-dimensional (2D) materials has recently grown to include topological insulators and semimetals. Their incorporation in special device geometries may lead to novel quantum electronics with enhanced functionalities. Weyl semimetals, in particular, offer the most robust form of topological protection. Recent results from our group indicate that Weyl nodes should be observable at room temperature in thin molybdenum ditelluride (MoTe₂) and are furthermore tunable by changing dimensionality. Weyl nodes correspond to points of bulk band degeneracy and are separated in momentum space. In this joint project with Dr. Andrea Damascelli’s group at the University of British Columbia (UBC), we utilize micro-angle-resolved photoemission spectroscopy (micro-ARPES) to image in momentum space the Weyl nodes and surface arcs of MoTe₂ and further investigate changes induced by lower dimensionality. Once the Weyl nodes are mapped, we perform transport measurements and utilize scanning photocurrent microscopy to image novel photogalvanic effects induced by the Weyl points in real space. We expect this project will pave the way for future materials exploration and device development that exploits the unique properties of 2D materials through combined ARPES and nanoscale device transport studies.

Figure 1. Sample device geometry. MoTe₂ flakes of various thicknesses are transferred on prepatterned gold electrodes deposited on a hexagonal boron nitride (BN)/graphite (Gr) heterostructure and capped with single-layer hBN. The bottom layers provide an ultra-flat substrate for the MoTe₂.