Mechanical dissipation from charge and spin transitions in oxygen deficient SrTiO_3

TL;DR

This study observes voltage-dependent dissipation peaks in oxygen-deficient SrTiO_3 at low temperatures, attributed to tip-induced charge and spin transitions in oxygen vacancy-related quantum dots, revealing new insights into non-contact friction mechanisms.

Contribution

It reports the first observation of dissipation peaks linked to charge and spin transitions in oxygen vacancies on SrTiO_3 surfaces at cryogenic temperatures.

Findings

Dissipation peaks depend on tip-surface distance and voltage.

Charge and spin state transitions are induced by the AFM tip.

Potential for new applications in nanoscale friction control.

Abstract

Bodies in relative motion separated by a gap of a few nanometers can experience a tiny friction force. This non-contact dissipation can have various origins and can be successfully measured by a sensitive pendulum atomic force microscope tip oscillating laterally above the surface. Here, we report on the observation of dissipation peaks at selected voltage-dependent tip-surface distances for oxygen-deficient strontium titanate (SrTiO_3) surface at low temperatures (T = 5K). The observed dissipation peaks are attributed to tip-induced charge and spin state transitions in quantum-dot-like entities formed by single oxygen vacancies (and clusters thereof, possibly through a collective mechanism) at the SrTiO_3 surface, which in view of technological and fundamental research relevance of the material opens important avenues for further studies and applications.