Stationary phase-kink states and dynamical phase transitions controlled by surface impedance in THz wave emission from intrinsic Josephson junctions

TL;DR

This study numerically investigates how surface impedance influences stationary states and THz emission in intrinsic Josephson junctions, revealing stable phase-kink states and optimal conditions for emission strength.

Contribution

It demonstrates the stability of different phase states under varying surface impedance and bias current, and maps the dynamical phase diagram for THz emission optimization.

Findings

McCumber-like state stable at low current and impedance

Pi-phase-kink state stable at higher current and impedance

Optimal surface impedance for strongest emission identified

Abstract

As possible states to characterize THz wave emission from intrinsic Josephson junctions without external fields, the McCumber-like state and $\pi$-phase-kink state have been proposed. In the present article it is numerically shown that both states are stationary according to the bias current $J$ and surface impedance $Z$. The McCumber-like state is stable for low $J$ and small $Z$. For higher $J$, the $\pi$-phase-kink state accompanied with symmetry breaking along the c axis is stable even for Z=1, though strong emission in the vicinity of cavity resonance points only takes place for larger $Z$. Different emission behaviors for Z=1 and 10 are precisely compared. The dynamical phase diagram for $1 \le Z \le 10$ and the optimal value of $Z$ for the strongest emission are also evaluated.