Alternating dynamic state in intrinsic Josephson-junction stacks self-generated by internal resonance

TL;DR

This paper investigates how internal cavity resonance in intrinsic Josephson-junction stacks induces an alternating coherent state, enhancing electromagnetic radiation in the terahertz range by promoting synchronized phase oscillations.

Contribution

It reveals the spontaneous formation of an alternating state with a static phase shift, advancing understanding of resonance-induced synchronization in high-temperature superconductor junction stacks.

Findings

Formation of an alternating coherent state with a static phase shift.

Homogeneous electric and magnetic fields across junctions.

Enhanced energy transfer into cavity resonance leading to strong resonance features.

Abstract

Intrinsic Josephson-junction stacks realized in high-temperature superconductors provide a very attractive base for developing coherent sources of electromagnetic radiation in the terahertz frequency range. A promising way to synchronize phase oscillations in all the junctions is to excite an internal cavity resonance. We demonstrate that this resonance promotes the formation of an alternating coherent state, in which the system spontaneously splits into two subsystems with different phase-oscillation patterns. There is a static phase shift between the oscillations in the two subsystems which changes from 0 to $2\pi$ in a narrow region near the stack center. The oscillating electric and magnetic fields are almost homogeneous in all the junctions. The formation of this state promotes efficient pumping of the energy into the cavity resonance leading to strong resonance features in the current-voltage dependence.