THz emission from intrinsic Josephson junctions at zero magnetic field via breather auto-oscillations

TL;DR

This paper introduces a novel mechanism for generating intense terahertz radiation from intrinsic Josephson junctions at zero magnetic field, involving breather auto-oscillations that enable power conversion.

Contribution

It proposes that breather auto-oscillations spontaneously break phase homogeneity, allowing dc-to-ac power conversion and explaining recent THz emission observations.

Findings

Breather auto-oscillations facilitate THz emission at zero magnetic field.

The mechanism accounts for features of THz radiation from Bi2212 mesa structures.

Spontaneous phase symmetry breaking enables effective power conversion.

Abstract

I propose a new mechanism of intense high-frequency electromagnetic wave generation by spatially uniform stacked Josephson junctions at zero magnetic field. The ac-Josephson effect converts the dc-bias voltage into ac-supercurrent, however, in the absence of spatial variation of Josephson phase difference, does not provide dc-to-ac power conversion, needed for emission of electromagnetic waves. Here I demonstrate that at geometrical resonance conditions, the spatial homogeneity of phase can be spontaneously broken by appearance of breathers (bound fluxon-antifluxon pairs), facilitating effective dc-to-ac power conversion. The proposed mechanism explains all major features of recently observed THz radiation from large area Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ mesa structures.