In-plane dissipation as a possible synchronization mechanism for terahertz radiation from intrinsic Josephson junctions of layered superconductors

Strong terahertz radiation from the mesa structure of a Bi ₂Sr ₂CaCu ₂O _8+δ single crystal has been observed recently, where the mesa intrinsically forms a cavity. For a thick mesa of a large number of junctions, there are many cavity modes with different wave vectors along the c axis corresponding to almost the same bias voltages. The mechanism responsible for exciting the uniform mode which radiates coherent terahertz waves in experiments is unknown. In this paper, we show that the in-plane dissipation selects the uniform mode. For perturbations with nonzero wave numbers along the c axis, the in-plane dissipations are significantly enhanced, which prevents the excitation of corresponding cavity modes. Our analytical results are confirmed by numerical simulations.