Subgap structures in the current-voltage characteristic of the intrinsic Josephson effect due to phonons

Abstract

A modified RSJ-model for the coupling of intrinsic Josephson oscillations and c-axis phonons in the high-T_c superconductors Tl_2Ba_2Ca_2Cu_3O_{10+\delta} and Bi_2Sr_2CaCu_2O_{8+\delta} is deveoped. This provides a very good explanation for recently reported subgap structures in the I-V-characteristic of the c-axis transport. It turns out that the voltages of these structures coincide with the eigenfrequencies of longitudinal optical phonons, providing a new measurement technique for this quantity. The significantly enhanced microwave emission at the subgap structures in both the GHz and THz region is discussed.Comment: correction of minor misprints, revtex, 3 pages, two postscript figures, aps, epsf, Contributed Paper to the "International Symposion on the Intrinsic Josphson effect and THz Plasma Oscillations", 22-25 February 1997, Sendai, Japan; to be published in Physica