Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe<sub>2</sub> on SrTiO<sub>3</sub> (001).
basic_science · Level V
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- Record sourced from PubMed, PMID 33044080.
- Also identified by DOI 10.1021/acs.nanolett.0c02741.
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Abstract
Interfacial polarons have been demonstrated to play important roles in heterostructures containing polar substrates. However, most of polarons found so far are diffusive large polarons; the discovery and investigation of small polarons at interfaces are scarce. Herein, we report the emergence of interfacial polarons in monolayer SnSe<sub>2</sub> epitaxially grown on Nb-doped SrTiO<sub>3</sub> (STO) surface using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). ARPES spectra taken on this heterointerface reveal a nearly flat in-gap band correlated with a significant charge modulation in real space as observed with STM. An interfacial polaronic model is proposed to ascribe this in-gap band to the formation of self-trapped small polarons induced by charge accumulation and electron-phonon coupling at the van der Waals interface of SnSe<sub>2</sub> and STO. Such a mechanism to form interfacial polaron is expected to generally exist in similar van der Waals heterojunctions consisting of layered 2D materials and polar substrates.