UC Riverside

In this dissertation, I discuss two comprehensive investigations that aim to advance ourunderstanding of photocurrent generation in complex heterostructure material systems. I first introduce our novel microscopy method to map photocurrent streamlines in ultrathin bilayer magnetic devices made of platinum on yttrium iron garnet (YIG). Utilizing scanning photovoltage microscopy with a rotating magnetic field, we achieve the first-ever direct imaging of photocurrent flow patterns. These streamlines exhibit complex behaviors such as contortion, compression, and expansion, depending on the device geometry providing unprecedented insights into the charge flow in optoelectronic systems. Second, I describe measurements of photocurrent generation at the interface of two semimetals: WTe2 (a Weyl semimetal) and graphene (a Dirac semimetal). By examining the detailed behavior of the photocurrent characteristics, we uncover how this hybrid semimetal system allows for an interlayer photovoltaic effect, reminiscent of semiconductor systems. Bridging these two investigations, we find that photocurrent generation is well described by the Shockley-Ramo theorem for conductors, thus providing a foundational framework for future photogeneration studies in complex heterostructure optoelectronic devices