Effect of thermal inhomogeneity for THz radiation from intrinsic Josephson junction stacks of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$

TL;DR

This study investigates how thermal inhomogeneity affects terahertz radiation from intrinsic Josephson junction stacks in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, highlighting the role of electrode thickness and local heating in phase synchronization.

Contribution

It reveals that thin electrodes facilitate terahertz radiation by promoting thermal inhomogeneity, which aids phase kink synchronization, unlike thicker electrodes that inhibit radiation.

Findings

Thin electrodes enable terahertz radiation and voltage jumps.

Thick electrodes suppress radiation and voltage jumps.

Local temperature rise is key to phase synchronization.

Abstract

Terahertz radiation from the mesa structures of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ is detected in samples with thin electrodes $< 100$ nm. In samples with thick electrodes $\simeq$ 400 nm, neither radiations nor voltage jumps in current-voltage characteristics are detected. This suggests that the thin electrode helps excite the Josephson plasma oscillation as a result of the poor heat flow through the electrode. The shielding effect by the electrode is not essential. We consider that the local temperature rise is the origin of the synchronization of the phase kink for terahertz radiation.