Phase Locking in Systems of Inductively Coupled Long Josephson Junctions

We studied the increase of coherent emission from the stack of intrinsic Josephson junctions in high-temperature superconductors in the vicinity of overheated places (hot spots). We numerically investigated the IV-characteristics and power of emission from two inductively coupled long Josephson junctions heated at one end. Another end of the stack always had the temperature 4.2 K. We found both odd and even zero-field steps in IV-characteristics of the stack and coherent emission at zero-field steps. When the difference of temperatures between ends was small, there were even zero-field steps, and at large difference of temperatures, only odd steps appeared. Coherent emission from the heated end of the system was stronger than that from the cold end. We found that the increase of the coherent emission appeared due to the increase of the amplitude of voltage oscillations.