Three-dimensional phase-kink state in a thick stack of Josephson junctions and terahertz radiation

Abstract

The dynamics of superconductivity phase in thick stack of Josephson junctions with strong inductive coupling, such as the one realized in layered high-Tc cuprates and possibly the recently discovered FeAs-based superconductors, is investigated under a c-axis bias voltage and in the absence of an external magnetic field. The kink state found previously by the present authors is extended to three dimensions for both rectangular and cylindrical geometries. The IV characteristics are calculated and the distributions of electromagnetic field inside the samples are clarified. The solution for a cylindrical mesa exhibits a higher resonating frequency than that of a square mesa with the same linear size by a factor of ∼ 2.4. More importantly, from the radius dependence of the resonance frequency for the cylinder geometry it is possible to confirm directly the kink state, and thus to reveal the mechanism of the strong radiation discovered in recent experiments.

Geometrical Resonance Conditions for THz Radiation from the Intrinsic Josephson Junctions inBi2Sr2CaCu2O8+δ

“…Hence, the radiation at higher harmonics arises solely from the uniform ac Josephson current source, but the larger intensity radiation at the fundamental frequency arises from both the uniform ac Josephson and nonuniform cavity sources. This experimental evidence clarifies unambiguously that the THz radiation is mainly generated by the uniform part of the ac Josephson current, in sharp contrast to a number of theoretical predictions [9,[18][19][20]. Further studies of the polarization, coherence, and spatial radiation patterns of the higher harmonics could provide supporting information for these conclusions.…”

“…In all previous studies of rectangular mesas [1,5,8], it was therefore not possible to unambiguously determine the primary radiation mechanism. Comparisons of the angular distributions of the observed and predicted radiation can also provide information as to the relative importance of the two radiation mechanisms [6,7,9].…”

Generation of electromagnetic waves from 0.3 to 1.6 terahertz with a high-Tc superconducting Bi2Sr2CaCu2O8+δ intrinsic Josephson junction emitter

“…The intrinsic Josephson junction (IJJ) terahertz (THz) emitter (IJJ-THz emitter) based on the IJJs present in the high-T c superconductor Bi 2 Sr 2 CaCu 2 O 8þd (Bi2212) [1][2][3] has been developed experimentally and theoretically. [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] So far, its demonstrated radiation characteristics are the f range from 0.3 to 1.0 THz, 4,22,23 the maximum P of $30 lW, [19][20][21][22] and coherent, continuous-wave emission with a spectral width of less than 0.5 GHz. 12,13 Recently, by synchronizing the emissions from a three-mesa array, P $ 610 lW was reported.…”

Improved excitation mode selectivity of high-Tc superconducting terahertz emitters

“…The IJJ-THz emitters based upon superconducting Bi2212 single crystals have intensively been developed both experimentally and theoretically. [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86] So far, the best performance has been achieved within the frequency range from 0.3 to 11 THz, [11][12][13]34,35,39 with the maximum output power of $30 lW, [31][32][33][34]39 and with a spectral width of the coherent and continuous emission of THz radiation that is generally less than 0.5 GHz, and under appropriate conditions, it was reported to be narrower than 23 MHz and possibly even 6 MHz. [23][24][25] Furthermore, a synchronized operation of an array of three such emitters was reported to yield the greatly enhanced power of 610 lW.…”