Quantum Tera-Hertz electrodynamics in Layered Superconductors
  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. 
Sergey Savel'ev, A.L. Rakhmanov, Franco Nori