Quantum Tera-Hertz electrodynamics in Layered Superconductors

TL;DR

This paper develops a quantum field theory for Josephson plasma waves in layered superconductors, revealing interactions between different bosonic modes and proposing a mechanism to enhance macroscopic quantum tunneling, explaining recent experimental observations.

Contribution

It introduces a novel quantum electrodynamics-like framework for JPWs in layered superconductors and explains the nonlinear dependence of tunneling rates on junction number.

Findings

Derived a quantum field theory for JPWs in layered superconductors.

Calculated decay and scattering amplitudes of JPWs.

Explained the nonlinear MQT escape rate dependence on junction number.

Abstract

In close analogy to quantum electrodynamics, we derive a quantum field theory of Josephson plasma waves (JPWs) in layered superconductors (LSCs), which describes two types of interacting JPW bosonic quanta: one massive and the other almost-massless. We also calculate the amplitude of their decay and scattering. We propose a mechanism of enhancement of macroscopic quantum tunneling (MQT) in stacks of intrinsic Josephson-junctions (SIJJs). Due to the long-range interactions between many junctions in the LSCs, the calculated MQT escape rate $\Gamma$ has a very nonlinear dependence on the number of junctions in the stack. This allows to quantitatively describe striking recent experiments in Bi2212 stacks.