Quasiparticle and excitonic properties of monolayer SrTiO₃

Author(s)

Lorenzo Varrassi, Peitao Liu, Cesare Franchini

Abstract

SrTiO3 is one of the most studied transition metal oxides. Recently, a breakthrough was achieved with the fabrication of freestanding SrTiO3 ultrathin films down to the monolayer limit. However, the many-body effects on the quasiparticle and optical properties of monolayer SrTiO3 remain unexplored. Using state-of-the-art many-body perturbation theory in the GW approximation combined with the Bethe-Salpeter equation, we study the quasiparticle band structure, optical, and excitonic properties of monolayer SrTiO3. We show that quasiparticle corrections significantly alter the band-structure topology; however, the widely used diagonal G0W0 approach yields unphysical band dispersions. The correct band dispersions are restored only by taking into account the off-diagonal elements of the self-energy. The optical properties are studied both in the optical limit and for finite momenta by computing the electron energy loss spectra. We find that the imaginary part of two-dimensional polarizability at the long wavelength limit is dominated by three strongly bound excitonic peaks and the direct optical gap is associated to a bright exciton state with a large binding energy of 0.93 eV. We discuss the character of the excitonic peaks via the contributing interband transitions and reveal that the lowest bound excitonic state becomes dark for finite momenta along Γ-M, while the other two excitonic peaks disperse to higher energies and eventually merge for momenta close to M.

Organisation(s)

Computational Materials Physics

External organisation(s)

University of Bologna, Chinese Academy of Sciences (CAS)

Journal

Physical Review Materials

Volume

8

No. of pages

10

ISSN

2475-9953

DOI

https://doi.org/10.1103/PhysRevMaterials.8.024001

Publication date

02-2024

Peer reviewed

Yes

Austrian Fields of Science 2012

103018 Materials physics

ASJC Scopus subject areas

Materials Science(all), Physics and Astronomy (miscellaneous)

Portal url

https://ucrisportal.univie.ac.at/en/publications/quasiparticle-and-excitonic-properties-of-monolayer-srtio3(47f180dd-1460-4c16-9822-ef4b9250bfaf).html