Nontrivial in-plane-magnetic-field dependence of THz wave emission from intrinsic Josephson junctions controlled by surface impedance

TL;DR

This study investigates how surface impedance influences THz wave emission from intrinsic Josephson junctions under in-plane magnetic fields, revealing complex dependencies and phase transitions that affect emission intensity and resonance modes.

Contribution

It demonstrates the significant role of surface impedance in controlling emission characteristics and phase states in Josephson junctions, providing insights into optimizing THz emission.

Findings

Cavity resonance modes are stabilized for Z ≥ 3.

Fundamental mode yields the strongest emission.

A crossover in maximum intensity profile occurs around Z ≈ 50.

Abstract

In THz wave emission from intrinsic Josephson junctions in in-plane magnetic fields, emission intensity strongly depends on the surface impedance $Z$ similarly to the case without external magnetic fields. Cavity resonance modes are stabilized for $Z \ge 3$, and the fundamental mode gives the strongest emission. As the in-plane magnetic field increases for a fixed number of junctions, dynamical phase transitions seem to occur between the $\pi$-phase-kink state, various incommensurate phase-kink states, and in-phase state. As $Z$ varies, a crossover of the field profile of maximum intensity takes place for $Z \approx 50$ between characteristic peaks for smaller $Z$ (typically $Z \approx 30$) and monotonic decrease for larger $Z$ (typically $Z \approx 70$). The double-peak structure reported in experiments can be explained for Z=30 by finite-size analysis with respect to number of junctions.