Josephson emission with frequency span 1-11 THz from small Bi2Sr2CaCu2O8+δ mesa structures

E A Borodianskyi; V M Krasnov

doi:10.1038/s41467-017-01888-4

Josephson emission with frequency span 1-11 THz from small Bi₂Sr₂CaCu₂O_8+δ mesa structures

Nat Commun. 2017 Nov 23;8(1):1742. doi: 10.1038/s41467-017-01888-4.

Authors

E A Borodianskyi¹, V M Krasnov²

Affiliations

¹ Department of Physics, Stockholm University, AlbaNova University Center, SE-106 91, Stockholm, Sweden.
² Department of Physics, Stockholm University, AlbaNova University Center, SE-106 91, Stockholm, Sweden. Vladimir.Krasnov@fysik.su.se.

Abstract

Mesa structures made of Bi₂Sr₂CaCu₂O_8+δ high-temperature superconductor represent stacks of atomic scale intrinsic Josephson junctions. They can be used for generation of high-frequency electromagnetic waves. Here we analyze Josephson emission from small-but-high mesas (with a small area, but containing many stacked junctions). We have found strong evidence for tunable terahertz emission with a good efficacy in a record high-frequency span 1-11 THz, approaching the theoretical upper limit for this superconductor. Emission maxima correspond to in-phase cavity modes in the mesas, indicating coherent superradiant nature of the emission. We conclude that terahertz emission requires a threshold number of junctions N ~ 100. The threshold behavior is not present in the classical description of stacked Josephson junctions and suggests importance of laser-like cascade amplification of the photon number in the cavity.

Publication types

Research Support, Non-U.S. Gov't