Abstract
Despite its simple structure and low degree of electronic correlation, (STO) features collective phenomena linked to charge transport and, ultimately, superconductivity, that are not yet fully explained. Thus, a better insight into the nature of the quasiparticles shaping the electronic and conduction properties of STO is needed. We studied the low-energy excitations of bulk STO and of the two-dimensional electron gas (2DEG) by Ti edge resonant inelastic x-ray scattering. In all samples, we find the hallmark of polarons in the form of intense excitations, and a decrease of the LO3-mode electron-phonon coupling when going from insulating to highly conducting STO single crystals and heterostructures. Both results are attributed to the dynamic screening of the large polaron self-induced polarization, showing that the low-temperature physics of STO and STO-based 2DEGs is dominated by large polaron quasiparticles.
- Received 4 May 2020
- Revised 26 July 2020
- Accepted 14 August 2020
DOI:https://doi.org/10.1103/PhysRevLett.125.126401
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