Ab-initio calculation of all-optical time-resolved calorimetry of nanosized systems: Evidence of nanosecond-decoupling of electron and phonon temperatures

TL;DR

This paper presents ab-initio calculations of ultrafast thermal dynamics in nanoscale Cu systems, revealing a nanosecond-scale decoupling of electron and phonon temperatures at low temperatures, suggesting new experimental approaches.

Contribution

It introduces a theoretical framework for all-optical time-resolved nanocalorimetry, highlighting a significant electron-phonon decoupling time scale at low temperatures.

Findings

Electron-phonon temperature decoupling occurs on the nanosecond scale at 10 K.

Decoupling time scale is two orders of magnitude longer than in low-temperature transport.

Proposes time-domain experiments as an alternative to low-temperature transport measurements.

Abstract

The thermal dynamics induced by ultrashort laser pulses in nanoscale systems, i.e. all-optical time-resolved nanocalorimetry is theoretically investigated from 300 to 1.5 K. We report ab-initio calculations describing the temperature dependence of the electron-phonon interactions for Cu nanodisks supported on Si. The electrons and phonons temperatures are found to decouple on the ns time scale at 10 K, which is two orders of magnitude in excess with respect to that found for standard low-temperature transport experiments. By accounting for the physics behind our results we suggest an alternative route for overhauling the present knowledge of the electron-phonon decoupling mechanism in nanoscale systems by replacing the mK temperature requirements of conventional experiments with experiments in the time-domain.