Large Polarons as Key Quasiparticles in SrTiO3 and SrTiO3-Based Heterostructures

Andrey Geondzhian, Alessia Sambri, Gabriella M. De Luca, Roberto Di Capua, Emiliano Di Gennaro, Davide Betto, Matteo Rossi, Ying Ying Peng, Roberto Fumagalli, Nicholas B. Brookes, Lucio Braicovich, Keith Gilmore, Giacomo Ghiringhelli, and Marco Salluzzo
Phys. Rev. Lett. 125, 126401 – Published 15 September 2020
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Abstract

Despite its simple structure and low degree of electronic correlation, SrTiO3 (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 LaAlO3/SrTiO3 two-dimensional electron gas (2DEG) by Ti L3 edge resonant inelastic x-ray scattering. In all samples, we find the hallmark of polarons in the form of intense dd+phonon 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.

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  • Received 4 May 2020
  • Revised 26 July 2020
  • Accepted 14 August 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.126401

© 2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Andrey Geondzhian1, Alessia Sambri2, Gabriella M. De Luca3,2, Roberto Di Capua3,2, Emiliano Di Gennaro3,2, Davide Betto1,†, Matteo Rossi4,5, Ying Ying Peng4,6, Roberto Fumagalli4, Nicholas B. Brookes1, Lucio Braicovich1,4, Keith Gilmore1,7, Giacomo Ghiringhelli4,8, and Marco Salluzzo2,*

  • 1ESRF—The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
  • 2CNR-SPIN Complesso Monte-Santangelo via Cinthia, I-80126 Napoli, Italy
  • 3Dipartimento di Fisica “Ettore Pancini” Università di Napoli “Federico II”, Complesso Monte-Santangelo via Cinthia, I-80126 Napoli, Italy
  • 4Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
  • 5Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
  • 6International Center for Quantum Materials,School of Physics, Peking University, Beijing 100871, China
  • 7Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
  • 8CNR-SPIN, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy

  • *marco.salluzzo@spin.cnr.it
  • Present address: Max Planck Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.

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Issue

Vol. 125, Iss. 12 — 18 September 2020

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