Regensburg 2022 – scientific programme

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MA: Fachverband Magnetismus

MA 35: Poster 2

MA 35.69: Poster

Thursday, September 8, 2022, 16:00–18:00, P4

A Floquet Green's Function technique to study ESR spectra — •Jose Reina Galvez — Center for Quantum Nanoscience, Ewha University, Seoul, Republic of Korea

This poster presents a theoretical framework to describe experiments directed to controlling single-atom spin dynamics by electrical means using a scanning tunneling microscope. The model consists of a quantum impurity connected to electrodes while an electrical time-dependent bias is applied. The quantum impurity consists of a localized electronic state, with a Coulomb repulsion U term, connected magnetically to a localized spin S.

Applying the Heisenberg picture, in the limit of weak coupling between the impurity and the electrodes, Born-Markov approximation, a quantum master equation can be obtained. The rates in this equation are derived by the non-equilibrium Green's function formalism. The Floquet theorem is used to transform the differential equation into algebraic one.

We show results in two cases. The first case is just a single atomic orbital subjected to a time-dependent electric field, and the second case consists of a single atomic orbital coupled to a second spin-1/2. This first case reproduces the main experimental features Ti atoms on MgO/Ag (100) but in a sequential tunneling regime and for different U values. The second case directly addresses the experiments on two Ti atoms.

These calculations permit us to explore the effect of different parameters to reproduce experimental fingerprints of the ESR technique.