Vibronic exciton–phonon states in stack-engineered van der Waals heterojunction photodiodes

• Main Authors: Barati, Fatemeh, Arp, Trevor B., Su, Shanshan, Lake, Roger K., Aji, Vivek, van Grondelle, Rienk, Rudner, Mark S., Song, Justin Chien Wen, Gabor, Nathaniel M.
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2023
• Subjects: Science::Physics; Vibronic; Photocurrent
• Online Access: https://hdl.handle.net/10356/168546
• Institution: Nanyang Technological University

Stack engineering, an atomic-scale metamaterial strategy, enables the design of optical and electronic properties in van der Waals heterostructure devices. Here we reveal the optoelectronic effects of stacking-induced strong coupling between atomic motion and interlayer excitons in WSe2/MoSe2 heterojunction photodiodes. To do so, we introduce the photocurrent spectroscopy of a stack-engineered photodiode as a sensitive technique for probing interlayer excitons, enabling access to vibronic states typically found only in molecule-like systems. The vibronic states in our stack are manifest as a palisade of pronounced periodic sidebands in the photocurrent spectrum in frequency windows close to the interlayer exciton resonances and can be shifted "on demand" through the application of a perpendicular electric field via a source-drain bias voltage. The observation of multiple well-resolved sidebands as well as their ability to be shifted by applied voltages vividly demonstrates the emergence of interlayer exciton vibronic structure in a stack-engineered optoelectronic device.