Quasiparticle and optical band gaps of Sr$_{n+1}$Ti$_{n}$O$_{3n+1}$ from \textit{ab-initio} many-body perturbation theory

ORAL

Abstract

The Ruddlesden Popper homologous series Sr$_{n+1}$Ti$_{n}$O$_{3n+1}$ provides a unique opportunity to study the effect of dimensionality and confinement on the band gap and absorption spectrum of the complex oxide SrTiO$_3$. In this work, we use many-body perturbation theory within the \textit{GW} approximation and the Bethe-Salpeter equation (BSE) approach to study the electronic and optical properties of Sr$_{n+1}$Ti$_{n}$O$_{3n+1}$. We find that our \textit{GW}/BSE direct and indirect band gaps are in excellent agreement with measured direct and indirect optical gaps. We discuss technical aspects of the calculations such as convergence and starting-point dependence, and compare to higher levels of theory. In addition, we find a relatively large exciton binding energy of 500 meV for Sr$_2$TiO$_4$ ($n=1$). We explore the role of structural distortions and epitaxial strain in the properties of the localized exciton. Our work suggests that layered structures can provide a viable route for the design of complex oxide materials with desirable optoelectronic properties. This work is supported by DOE.

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Authors

  • Sebastian E Reyes-Lillo

    • Molecular Foundry, LBNL; Dept. of Physics, UC Berkeley

  • Tonatiuh Rangel

    • Lawrence Berkeley National Laboratory
    • Molecular Foundry, LBNL; Dept. of Physics, UC Berkeley
    • Lawrence Berkeley Natl Lab; UC Berkeley

  • Fabien Bruneval

    • Molecular Foundry, LBNL; Dept. of Physics, UC Berkeley; CEA, DEN, SRMP

  • Jeffrey Neaton

    • University of California, Berkeley; Lawrence Berkeley National Laboratory
    • Lawrence Berkeley Natl Lab/UC Berkeley
    • Physics Department, UC Berkeley, The Molecular Foundry, LBNL \& Kavli Energy NanoSciences Institute at Berkeley, Berkeley, CA
    • Molecular Foundry, Lawrence Berkeley National Lab; Department of Physics, University of California Berkeley; Kavli Energy NanoSciences Insitute
    • Molecular Foundry, LBNL; Dept. of Physics, UC Berkeley; Kavli ENSI
    • UC Berkeley; Molecular Foundry, LBNL; Kavli Energy Nanosciences Institute at Berkeley
    • Dept. of Physics, UC Berkeley \& Lawrence Berkeley National Lab (USA)
    • Molecular Foundry, LBNL, Dept. of Physics, UC-Berkeley and Kavli ESNI at Berkeley
    • Molecular Foundry, Lawrence Berkeley National Laboratory
    • Physics Department, UC Berkeley; Molecular Foundry, Lawrence Berkeley National Lab; Kavli Energy NanoSciences Institute at Berkeley