A Dynamical Cross-over Regime in the Transmission and Reflection Spectra of Evanescent Waves with 2D Arrays of Josephson Junctions

TL;DR

This paper investigates a dynamical crossover in evanescent wave transmission through 2D Josephson junction arrays, revealing a power-dependent transition between phase-locked and unlocked states with implications for superconducting device control.

Contribution

It introduces the observation of a power-tunable crossover regime in Josephson junction arrays, linking spectral features to phase coherence transitions.

Findings

Evanescent waves are transmitted without loss at low power and temperature.

A second resonance emerges and grows with increasing power.

The crossover suggests a transition from phase-locked to phase-unlocked states.

Abstract

A dynamical cross-over regime is revealed when exposing a classical two-dimensional ordered Josephson junction (JJ) array to evanescent waves and tuning the incident microwave power. At the lowest possible temperature for these experiments, 1.1 K, and at the lowest power setting, -55 dBm, evanescent waves are transmitted without loss and the resonance exhibits a quality factor of ~ 4200. A second, smaller resonance, which evolves with increasing power from the main resonance, is also investigated. In contrast to the behavior of the main resonance, this second peak grows as the incident power is increased and does not maintain a fixed resonant frequency for temperatures less than the superconducting critical temperature of niobium. The tunability of both resonances is studied as a function of temperature and microwave power. Finally we speculate that this dynamical crossover regime is evidence of a transition between two states of phase coherence where at low microwave power the JJ arrays are phase locked and at high microwave power the JJ arrays are unlocked.