Enhancing Shift Current via Virtual Multiband Transitions
arxiv(2024)
摘要
Finding materials exhibiting substantial shift current holds the potential
for designing shift current-based photovoltaics that outperform conventional
solar cells. However, the myriad of factors governing shift current response
poses significant challenges in designing devices that showcase large shift
current. Here, we propose a general design principle that exploits
inter-orbital mixing to excite virtual multiband transitions in materials with
multiple flat bands to achieve enhanced shift current response. We further
explicitly relate this design principle to maximizing Wannier function spread
as expressed through the formalism of quantum geometry. We demonstrate the
viability of our design using a 1D stacked Rice-Mele model. Then, we consider a
concrete material realization - alternating angle twisted multilayer graphene
(TMG) - a natural platform to experimentally realize such an effect. We
identify a new set of twist angles at which the shift current response is
maximized via virtual transitions for each multilayer graphene and highlight
the importance of TMG as a promising material to achieve an enhanced shift
current response at terahertz frequencies. Our proposed mechanism also applies
to other 2D systems and can serve as a guiding principle for designing
multiband systems that exhibit enhanced shift current response.
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