Jose Reina Galvez

Affiliation: CFM – Materials Physics Center

Date: February 17, 2021; 17:00 – 18:00

Floquet theory applied to ESR

Electron spin resonance (ESR) with the STM is a revolutionary technique that is permitting us to have unprecedented insight into quantum dynamical processes. To really achieve this goal, theory can be instrumental. To this end, we have developed a theory that computes the time-dependent electron current through a quantum system. The theory is based on the Floquet formalism that allows us to treat a complex time dependence, and it also uses non-equilibrium Green’s functions to deal with realistic bias drops in the quantum system. We can then easily identify the behavior of the electronic current with the actual quantum dynamics.

In this talk, I will first present the results of a spin-1/2 driven by a harmonic time-dependent bias. We will analyze the results of these calculations, showing the main ingredients of the theory. Then, we will move to two spins interacting via an exchange interaction and reproduce the experiments by Bae et al 2018. We evaluate the von Neumann entropy and show that entanglement is needed, but it is rather constant for all the cases evaluated here. Moreover, we show why the Rabi’s frequencies of the different transitions are changing, which gives us a handle on the actual parameters controlling the dynamics of this two-spin system. We will briefly show other results on spin-1 and spin-2 systems to show the versatility of our approach as well as its predictive power.