Quasiparticle dynamics and spin-orbital texture of the SrTiO3 two-dimensional electron gas

This work was supported by the UK EPSRC (EP/I031014/1), the ERC (207901), the SNSF (200021-146995), the Scottish Funding Council, The Thailand Research Fund (RSA5680052), Office of the Higher Education Commission, Suranaree Univerisity of Technology and the Japan Society for the promotion of Science (JSPS), through the ‘Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program)’, initiated by the council for Science and Technology policy (CSTP). P.D.C.K. acknowledges support from the Royal Society through a University Research Fellowship (UF120096).Two-dimensional electron gases (2DEGs) in SrTiO3 have become model systems for engineering emergent behaviour in complex transition metal oxides. Understanding the collective interactions that enable this, however, has thus far proved elusive. Here we demonstrate that angle-resolved photoemission can directly image the quasiparticle dynamics of the d-electron subband ladder of this complex-oxide 2DEG. Combined with realistic tight-binding supercell calculations, we uncover how quantum confinement and inversion symmetry breaking collectively tune the delicate interplay of charge, spin, orbital and lattice degrees of freedom in this system. We reveal how they lead to pronounced orbital ordering, mediate an orbitally enhanced Rashba splitting with complex subband-dependent spin-orbital textures and markedly change the character of electron-phonon coupling, co-operatively shaping the low-energy electronic structure of the 2DEG. Our results allow for a unified understanding of spectroscopic and transport measurements across different classes of SrTiO3-based 2DEGs, and yield new microscopic insights on their functional properties.PostprintPeer reviewe