Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 19: Overview Talk Felix Baumberger
O 19.1: Hauptvortrag
Dienstag, 19. März 2024, 09:30–10:15, HE 101
Quasiparticle dynamics and spin-orbital texture of 2D electron liquids at surfaces — •Felix Baumberger — Department of Quantum Matter Physics, University of Geneva, Switzerland — Swiss Light Source, Paul Scherrer Institute, Switzerland
Two-dimensional electron liquids (2DELs) at interfaces of transition metal oxides are foundational for the field of oxide electronics but proved notoriously hard to study spectroscopically. Here, we show that surface doping of SrTiO3 and KTaO3 can be used to replicate the electrostatic boundary conditions stabilizing the prototypical interface 2DELs in these oxides. Our angle resolved photoemission data on different SrTiO3 and KTaO3 surfaces provide direct evidence for subband formation of the d-electrons with a surface orientation dependent lifting of the orbital degeneracy induced by quantum confinement. Modeling the experimental electronic structure, we uncover a complex spin-orbital texture on the Fermi surface and show that it determines the large spin charge conversion effect in SrTiO3. Tuning the 2DEL carrier density of SrTiO3(001) by controlling the oxygen vacancy concentration on the surface, we find a remarkably complex evolution of electron-phonon coupling from a coherent polaronic liquid at low carrier density to a more conventional metal with modest short range electron-phonon coupling at high density. These results support the notion that superconductivity at the LaAlO3 / SrTiO3 interface is phonon mediated.