Electron Spin Resonance

Ray LaPierre

Stefan Weichselbaumer, Petio Natzkin, Christoph W. Zollitsch +3 more

Engineering and understanding microwave resonators is essential for the efficient electron-spin control and readout in electron-spin-resonance (ESR) spectroscopy. This work, focused on superconducting planar microresonators, presents finite-element simulations modeling the spin-photon coupling rate, in quantitative agreement with experimental data. Three resonator designs are optimized to address spectroscopy applications in $\ensuremath{\mu}$m-thick samples, with one exhibiting notably good magnetic field homogeneity at microwave frequencies.

Saba Taherpour, Denis Janković, Jose Reina-Galvez +2 more

Electron spin resonance in scanning tunneling microscopy enabled the study of electronic transitions of magnetic impurities on surfaces at the atomic scale. This ESR-STM technique allows to spectroscopically probe and coherently manipulate spins using an all-electrical method without oscillating external magnetic driving fields. Here, we aim to review recent advancements in ESR-STM. We will discuss possible fundamental mechanisms by which the electric field drives spin resonance based on Heisenberg exchange, Kondo scattering, and Anderson impurity models. We validate theoretical predictions against experimental observations, to understand how electronic correlations, spin exchange, and many-body effects manifest in ESR-STM signals. After reviewing coherent spin control in the STM junction, we discuss potential applications of the ESR-STM method for coherent multi-spin control which enables multiple-qubit operations. Finally, we address recent developments in coupled electron-nuclear spin systems, including hyperfine-resolved ESR spectroscopy, and the driving and polarization of nuclear spins in ESR-STM.

Arno Böhm

A. T. Asfaw, A. J. Sigillito, A. M. Tyryshkin +2 more

In this work, we demonstrate the use of frequency-tunable superconducting NbTiN coplanar waveguide microresonators for multi-frequency pulsed electron spin resonance (ESR) experiments. By applying a bias current to the center pin, the resonance frequency (∼7.6 GHz) can be continuously tuned by as much as 95 MHz in 270 ns without a change in the quality factor of 3000 at 2 K. We demonstrate the ESR performance of our resonators by measuring donor spin ensembles in silicon and show that adiabatic pulses can be used to overcome magnetic field inhomogeneities and microwave power limitations due to the applied bias current. We take advantage of the rapid tunability of these resonators to manipulate both phosphorus and arsenic spins in a single pulse sequence, demonstrating pulsed double electron-electron resonance. Our NbTiN resonator design is useful for multi-frequency pulsed ESR and should also have applications in experiments where spin ensembles are used as quantum memories.