Spin-dependent anisotropic electron-phonon coupling in KTaO${}_3$

Abstract

KTaO${}_3$ (KTO) is an incipient ferroelectric, characterized by a softening of the lowest transverse optical (TO) mode with decreasing temperature. Cooper pairing in the recently discovered KTO-based heterostructures has been proposed to be mediated by the soft TO mode. Here we study the electron coupling to the zone-center odd-parity modes of bulk KTO by means of relativistic Density Functional Perturbation Theory (DFPT). The coupling to the soft TO mode is by far the largest, with comparable contributions from both intraband and interband processes. Remarkably, we find that for this mode, spin-non-conserving matrix elements are particularly relevant. We develop a three-band microscopic model with spin-orbit coupled $t_{2g}$ orbitals that reproduces the main features of the ab initio results. For the highest energy band, the coupling can be understood as a "dynamical" isotropic Rashba effect. In contrast, for the two lowest bands, the Rashba-like coupling becomes strongly anisotropic. The DFPT protocol implemented here enables the calculation of the full electron-phonon coupling matrix projected onto any mode of interest, and it is easily applicable to other systems.

19 pages, 11 figures

References in corpus (52)

• Maximally localized Wannier functions: Theory and applications
• Electric Field Control of the LaAlO${}_3$/SrTiO${}_3$ Interface Ground State
• Quantum criticality in ferroelectrics
• Physics of SrTiO${}_3$-based heterostructures and nanostructures: a review
• Discovery of two-dimensional anisotropic superconductivity at KTaO${}_3$ (111) interfaces
• Two-dimensional superconductivity at the surfaces of KTaO3 gated with ionic liquid
• Orbital effects in solids: basics, recent progress and opportunities
• A ferroelectric quantum phase transition inside the superconducting dome of Sr${}_{1-x}$Ca${}_x$TiO${}_{3-\delta }$
• Quantum critical origin of the superconducting dome in SrTiO${}_3$
• Electric field control of disorder-tunable superconductivity and the emergence of quantum metal at an oxide interface
• Parity-breaking phases of spin-orbit-coupled metals with gyrotropic, ferroelectric and multipolar orders
• Fermi surface of the most dilute superconductor
• Superconductivity in dilute SrTiO${}_3$: a review
• Odd-parity superconductivity in the vicinity of inversion symmetry breaking in spin-orbit-coupled systems
• Observation of two-dimensional superconductivity at the LaAlO3/KTaO3(110) heterointerface
• Superconductivity in three-dimensional spin-orbit coupled semimetals
• Electric Field Tuning of the Rashba Effect in the Polar Perovskite Structures
• Mixing of $t_{2g}$-$e_g$ orbitals in 4d and 5d transition metal oxides
• Rashba spin-splitting in ferroelectric oxides: from rationalizing to engineering
• Tunable superconductivity at the oxide-insulator/KTaO${}_3$ interface and its origin
• A possible mechanism for superconductivity in doped SrTiO3
• Superfluid stiffness of a KTaO3-based two-dimensional electron gas
• Band Structure and Spin-Orbital Texture of the (111)-KTaO3 Two-Dimensional Electron Gas
• Superconductivity at low density near a ferroelectric quantum critical point: doped SrTiO
• Spin-orbit-coupled ferroelectric superconductivity
• Anisotropic superconductivity mediated by ferroelectric fluctuations in cubic systems with spin-orbit coupling
• Isotope tuning of the superconducting dome of strontium titanate
• Superconductivity from energy fluctuations in dilute quantum critical polar metals
• Superconductivity near a ferroelectric quantum critical point in ultralow-density Dirac materials
• Electron-phonon interaction and longitudinal-transverse phonon splitting in doped semiconductors
• Enhanced Critical Field of Superconductivity at an Oxide Interface
• Superconductivity induced by fluctuations of momentum-based multipoles
• Orientation-dependent electron-phonon coupling in interfacial superconductors LaAlO3/KTaO3
• Theory of superconductivity mediated by Rashba coupling in incipient ferroelectrics
• Superconductivity enhancement in polar metal regions of Sr${}_{0.95}$Ba${}_{0.05}$TiO${}_3$ and Sr${}_{0.985}$Ca${}_{0.015}$TiO${}_3$ revealed by the systematic Nb doping
• Theory of superconductivity in doped quantum paraelectrics
• Electron-phonon interaction and phonons in 2d doped semiconductors
• Comment on "Superconductivity at low density near a ferroelectric quantum critical point: Doped SrTiO3"
• Superconducting dome in ferroelectric-type materials from soft mode instability
• Generalized Rashba Electron-Phonon Coupling and Superconductivity in Strontium Titanate
• Strongly enhanced Rashba splittings in oxide heterostructure: a tantalite monolayer on BaHfO${}_3$
• Multiband Quantum Criticality of Polar Metals
• Electronic subbands in the a-LaAlO${}_3$/KTaO${}_3$ interface revealed by quantum oscillations in high magnetic fields
• A theory of criticality for quantum ferroelectric metals
• Superconductivity at epitaxial LaTiO3-KTaO3 interfaces
• Lamellar fluctuations melt ferroelectricity
• Anisotropic Rashba coupling to polar modes in KTaO3
• Revealing subterahertz atomic vibrations in quantum paraelectrics by surface-sensitive spintronic terahertz spectroscopy
• Topological superconductivity from transverse optical phonons in oxide heterostructures
• Unconventional quantum oscillations and evidence of nonparabolic electronic states in quasi-two-dimensional electron system at complex oxide interfaces
• Phonon-Induced Collective Modes in Spin-Orbit Coupled Polar Metals
• Violation of Pauli Limit at KTaO3(110) Interfaces

Cited by in corpus (1)

• Superconductivity from the Slater mode: Application to KTaO3 heterostructures