Low-Temperature Saturation of the Dephasing Time and Effects of Microwave Radiation on Open Quantum Dots

TL;DR

This study investigates electron dephasing times in open quantum dots at very low temperatures, revealing saturation behavior and the effects of microwave radiation, which are primarily due to heating rather than direct dephasing.

Contribution

It demonstrates that microwave radiation affects quantum interference through heating effects, not direct dephasing, clarifying the cause of dephasing time saturation at low temperatures.

Findings

Dephasing time saturates below ~100 mK, independent of dot size.

Microwave radiation impacts interference via heating, not direct dephasing.

Joule heating from microwaves explains the observed dephasing effects.

Abstract

The dephasing time of electrons in open semiconductor quantum dots, measured using ballistic weak localization, is found to saturate below ~ 100 mK, roughly twice the electron base temperature, independent of dot size. Microwave radiation deliberately coupled to the dots affects quantum interference indistinguishably from elevated temperature, suggesting that direct dephasing due to radiation is not the cause of the observed saturation. Coulomb blockade measurements show that the applied microwaves create sufficient source drain voltages to account for dephasing due to Joule heating.