Anisotropic Rashba coupling to polar modes in KTaO3. (1st January 2023)

• Record Type: Journal Article
• Authors: Venditti, Giulia; Temperini, Maria Eleonora; Barone, Paolo; Lorenzana, Jose; Gastiasoro, Maria N
• Is Part Of: JPhys materials. Volume 6:Number 1(2023)
• Publication Date: 2023-01-01
• Subjects: Rashba coupling -- ferroelectric mode -- unconventional superconductivity; Solid state physics -- Periodicals; Materials science -- Periodicals; 530.41
• DOI: 10.1088/2515-7639/acb017
• Languages: English
• ISSNs: 2515-7639

Abstract

Abstract: Motivated by the discovery of superconductivity in KTaO3 -based heterostructures, we study a pairing mechanism based on spin-orbit assisted coupling between the conduction electrons and the ferroelectric (FE) modes present in the material. We use ab initio frozen-phonon computations to show a linear-in-momentum Rashba-like coupling with a strong angular dependence in momentum for the lower j = 3 / 2 manifold, deviating from the conventional isotropic Rashba model. This implies the Rashba-like interaction with the polar modes has substantial L = 3 cubic harmonic corrections, which we quantify for each electronic band. The strong anisotropy of the Rashba interaction is captured by a microscopic toy model for the t 2 g electrons. We find its origin to be the angular dependence in electronic momentum imposed by the kinetic term on the degenerate j = 3 / 2 manifold. A comparison between the toy model and ab initio results indicates that additional symmetry allowed terms beyond odd-parity spin-conserving inter-orbital hopping processes are needed to describe the Rashba-like polar interaction between the electrons and the soft FE mode.