Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 66: Oxide Surfaces 2
O 66.2: Vortrag
Donnerstag, 8. September 2022, 11:00–11:15, S053
Surface phonons and their coupling to the 2D electron liquid at the CTO/STO surface — •M. Döttling1, E. B. Guedes2,3, T. P. van Waas4,2, S. Poncé4,5, M. Caputo3,6, N. C. Plumb2, N. Marzari5, C. Berthod7, M. Radović2, J. H. Dil3,2, and K. Zakeri1 — 1PHI, Karlsruhe Institute of Technology — 2PSD, PSI — 3IPHYS, EPF Lausanne — 4IMCN, UC Louvain — 5THEOS, EPF Lausanne — 6Elettra, Trieste — 7DQMP, University of Geneva
Motivated by the recent discovery of a 2D electron liquid (2DEL) formed at the surface of CaTiO3/SrTiO3(001) heterostructure, we probed the phonon spectrum of the system by means of high-resolution electron energy-loss spectroscopy (HREELS). Our main aim was to address any possible interaction of 2DEL with phonons.
The HREELS measurements revealed the existence of the Fuchs-Kliewer (FK) phonon modes at the energies of 20, 60 and 93 meV. Interestingly, the Eliashberg-function α2 F(ω) constructed based on the quasiparticle band dispersion, probed by angle-resolved photoemission experiments, exhibits peaks at energies of 20, 60 and 80 meV.
The apparent redshift of the highest energy peak in α2 F(ω), compared to the 93 meV FK mode, can be attributed to the formation of band-gap states (BGS). Such states form upon photon irradiation at the same time as 2DEL is formed. This is shown by the simulated HREEL spectra including BGS. Our results demonstrate the importance of BGS and the necessity of their consideration in describing the properties of oxide heterostructures. Supported by DFG via Heisenberg Programme ZA 902/3-1, ZA 902/6-1 and ZA 902/5-1.