Combining Electron Spin Resonance Spectroscopy with Scanning Tunneling Microscopy at High Magnetic Fields

TL;DR

This paper advances electron spin resonance scanning tunneling microscopy (ESR-STM) by extending its frequency range beyond 100GHz, enabling high-field quantum spin studies with improved signal delivery and inelastic tunneling analysis.

Contribution

It introduces a general method to upgrade existing STM instruments for high-frequency ESR-STM operation up to 100GHz, enhancing capabilities for quantum spin research.

Findings

Extended ESR-STM frequency range beyond 100GHz.

Successful inelastic tunneling measurements with microwave-driven junctions.

Proof of principle demonstrations of high-field ESR-STM performance.

Abstract

Magnetic media remain a key in information storage and processing. The continuous increase of storage densities and the desire for quantum memories and computers pushes the limits of magnetic characterisation techniques. Ultimately, a tool which is capable of coherently manipulating and detecting individual quantum spins is needed. The scanning tunnelling microscope (STM) is the only technique which unites the prerequisites of high spatial and energy resolution, low temperature and high magnetic fields to achieve this goal. Limitations in the available frequency range for electron spin resonance STM (ESR-STM) mean that many instruments operate in the thermal noise regime. We resolve challenges in signal delivery to extend the operational frequency range of ESR-STM by more than a factor of two and up to 100GHz, making the Zeeman energy the dominant energy scale at achievable cryogenic temperatures of a few hundred millikelvin. We present a general method for augmenting existing instruments into ESR-STMs to investigate spin dynamics in the high-field limit. We demonstrate the performance of the instrument by analysing inelastic tunnelling in a junction driven by a microwave signal and provide proof of principle measurements for ESR-STM.