Electrical spin manipulation in double SrTiO$_3$/LaAlO$_3$ quantum dots

TL;DR

This study models spin dynamics in double quantum dots at the SrTiO$_3$/LaAlO$_3$ interface, revealing how electric fields induce spin flips via complex multi-photon processes and Landau-Zener transitions, with implications for quantum control.

Contribution

It provides a detailed numerical analysis of electric dipole spin resonance in double quantum dots, highlighting the effects of symmetry, magnetic field, and electric field amplitude on spin-flip mechanisms.

Findings

Single photon spin-flip transitions are forbidden in symmetric dots due to parity symmetry.

Asymmetry enables first-order singlet-triplet transitions and Rabi oscillations.

High magnetic fields and strong AC fields induce spin flips via Landau-Zener transitions.

Abstract

The spin dynamics in two electron double quantum dots embedded in two dimensional electron gas at the interface between SrTiO$_3$ and LaAlO$_3$ is studied by an exact numerical solution of the time-dependent Schr\"odinger equation, in the context of the electric dipole spin resonance experiment. Based on the three band model of $3d$-electrons localized at Ti ions on the square lattice we analyze in details the singlet-triplet transition induced by the AC electric field, in the magnetic field range close to the avoided crossing which appears as a result of the spin-orbit coupling. Our calculations show that for symmetric double quantum dots the single photon spin-flip transitions is prohibited due to the parity symmetry and the transition can occur only by the higher order two-photon processes. For a weakly asymmetric system, when the first order singlet-triplet transitions are released due to the parity symmetry breaking, the spin-flip transition has a character of the Rabi oscillations for a low electric field amplitude. As the amplitude is increased the frequency of the transition is blueshifted (redshifted) for the magnetic field below (above) the single-triplet avoided crossing. Interestingly, for a sufficiently high magnetic field and high AC field amplitude the electric field drives the system across the avoided crossing inducing the spin-flip by the Landau-Zener-Stueckelberg-Majorana transitions with 100\% spin flip probability for a slow sweep. Finally, the optimization of the geometrical parameters of the system with respect to the time of spin-flip of its fidelity is also presented.