Quenched Excitons in WSe2/α-RuCl3 Heterostructures Revealed by Multimessenger Nanoscopy

Aaron J. Sternbach, Rocco A. Vitalone, Sara Shabani, Jin Zhang, Thomas P. Darlington, Samuel L. Moore, Sang Hoon Chae, Eric Seewald, Xiaodong Xu, Cory R. Dean, Xiaoyang Zhu, Angel Rubio, James Hone, Abhay N. Pasupathy, P. James Schuck and D. N. Basov

Nano Letters 23, 5070 (2023)
We investigate heterostructures composed of monolayer WSe2 stacked on α-RuCl3 using a combination of Terahertz (THz) and infrared (IR) nanospectroscopy and imaging, scanning tunneling spectroscopy (STS), and photoluminescence (PL). Our observations reveal itinerant carriers in the heterostructure prompted by charge transfer across the WSe2/α-RuCl3 interface. Local STS measurements show the Fermi level is shifted to the valence band edge of WSe2 which is consistent with p-type doping and verified by density functional theory (DFT) calculations. We observe prominent resonances in near-IR nano-optical and PL spectra, which are associated with the A-exciton of WSe2. We identify a concomitant, near total, quenching of the A-exciton resonance in the WSe2/α-RuCl3 heterostructure. Our nano-optical measurements show that the charge-transfer doping vanishes while excitonic resonances exhibit near-total recovery in “nanobubbles”, where WSe2 and α-RuCl3 are separated by nanometer distances. Our broadband nanoinfrared inquiry elucidates local electrodynamics of excitons and an electron–hole plasma in the WSe2/α-RuCl3 system.