Nonlinear optical phonon spectroscopy revealing polaronic signatures of the LaAlO₃/SrTiO₃ interface.

ABSTRACT: We report the direct observation of lattice phonons confined at LaAlO₃/SrTiO₃ (LAO/STO) interfaces and STO surfaces using the sum-frequency phonon spectroscopy. This interface-specific nonlinear optical technique unveiled phonon modes localized within a few monolayers at the interface, with inherent sensitivity to the coupling between lattice and charge degrees of freedom. Spectral evolution across the insulator-to-metal transition at LAO/STO interface revealed an electronic reconstruction at the subcritical LAO thickness, as well as strong polaronic signatures upon formation of the two-dimensional electron gas. We further discovered a characteristic lattice mode from interfacial oxygen vacancies, enabling us to probe such important structural defects in situ. Our stu

SUBMITTER: Liu X 

PROVIDER: S-EPMC10256162 | biostudies-literature | 2023 Jun

REPOSITORIES: biostudies-literature