In-plane dissipation as a possible synchronization mechanism for   terahertz radiation from intrinsic Josephson junctions of layered   superconductors
  Strong terahertz radiation from mesa structure of $\rm{Bi_2Sr_2CaCu_2O_{8+\delta}}$ single crystal has been observed recently, where the mesa intrinsically forms a cavity. For a thick mesa of large number of junctions, there are many cavity modes with different wave vectors along the c-axis corresponding to almost degenerate bias voltages. The mechanism responsible for exciting the uniform mode which radiates coherent terahertz waves in experiments is unknown. In this work, we show that the in-plane dissipation selects the uniform mode. For perturbations with non-zero wave numbers along the c-axis, the in-plane dissipations are significantly enhanced, which prevent the excitation of corresponding cavity modes. Our analytical results are confirmed by numerical simulations. 
Shi-Zeng Lin and Xiao Hu
cond-mat.supr-con cond-mat.mtrl-sci