# Probing two-level systems with electron spin inversion recovery of defects at the Si/SiO$_2$ interface

## TL;DR

This paper uses electron spin relaxation measurements at the Si/SiO2 interface to investigate two-level systems in amorphous materials, revealing their properties and impact on device noise and decoherence.

## Contribution

It introduces a novel experimental approach and a model to characterize the spatial, energetic, and temperature-dependent properties of TLSs near interfaces.

## Key findings

- Non-exponential spin inversion recovery observed
- Model quantifies TLS localization and concentration
- TLS properties vary with temperature

## Abstract

The main feature of amorphous materials is the presence of excess vibrational modes at low energies, giving rise to the so called "boson peak" in neutron and optical spectroscopy. These same modes manifest themselves as two level systems (TLSs) causing noise and decoherence in qubits and other sensitive devices. Here we present an experiment that uses the spin relaxation of dangling bonds at the Si/(amorphous)SiO$_2$ interface as a probe of TLSs. We introduce a model that is able to explain the observed non-exponential electron spin inversion recovery and provides a measure of the degree of spatial localization and concentration of the TLSs close to the interface, their maximum energy and its temperature dependence.