Phonon-polarons and plasmon-polarons in the ARPES spectra of transition metal oxides

DIPC Seminars

Feliciano GIUSTINO, University of Oxford
Donostia International Physics Center
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Phonon-polarons and plasmon-polarons in the ARPES spectra of transition metal oxides The interaction between electrons and bosons is a central concept in condensed matter physics. For example, the signatures of electron-phonon interactions are ubiquitous in photoelectron spectra, light absorption, emission, and scattering spectra, as well as electron tunnelling spectra. Until recently the theoretical analysis of such interactions and their consequences could only be carried out using empirical models such as the classic Frohlich Hamiltonian. However, during the past decade, the development of new computational techniques and new theoretical approaches has enabled the study of electron- boson interactions entirely from first principles [1]. In this talk I will present two recent examples of first-principles calculations of electron-boson interactions. In the first example I will discuss recent work on the interaction between electrons and polar optical phonons in titanium dioxide [2,3,4]. Here we succeeded to reproduce, entirely from first principles, recent angle-resolved photoemission data on n-doped anatase, and we identified the origin of the crossover from the polaronic regime to the Fermi liquid regime as a function of carrier density. In the second example I will describe the recent observation of both phonon polarons and plasmon polarons in ferromagnetic EuO, and our interpretation of the ARPES spectra based on first- principles calculations [5]. These studies constitute the first steps towards fully ab-initio calculations of phonon-polarons and plasmon-polarons in transition metal oxides, and set the stage for controlling electron-boson physics in oxide electronics. [1] F. Giustino, Electron-phonon interactions from first principles, Rev. Mod. Phys. 89, 015003 (2017). [2] C. Verdi, F. Giustino, Fröhlich electron-phonon vertex from first principles, Phys. Rev. Lett. 115, 176401 (2015). [3] C. Verdi, F. Caruso, F. Giustino, Origin of the crossover from polarons to Fermi liquids in transition metal oxides. Nat. Commun. 8, 15769 (2017). [4] F. Caruso, C. Verdi, S. Poncé, F. Giustino, Electron-plasmon and electron-phonon satellites in the angle resolved photoelectron spectra of n-doped anatase TiO2, Phys. Rev. B, 97, 165113 (2018). [5] J. M. Riley, F. Caruso, C. Verdi, L. B. Duffy, M. D. Watson, L. Bawden, K. Volckaert, G. van der Laan, T. Hesjedal, M. Hoesch, F. Giustino, and P. D. C. King, Crossover from lattice to plasmonic polarons of a spin-polarised electron gas in ferromagnetic EuO, Nat. Commun. 9, 2305 (2018). Host: Asier Eiguren Goienetxea