Nonequilibrium Microwave Emission from DC-Biased High T_c YBa₂Cu₃O_7-y Junctions

Abstract

Non-relativistic Compton profiles (in the impulse approximation) have been calculated for the He, Li, Be, B and Ne atoms from the numerical wavefunctions generated by four local density models for exchange correlation. Two of the models were simple P ' '~ schemes (p is the electron charge density): Xa,'l (the common form of the X a approximation) and X x / 2 ( X a with a stepfunction radial dependence for a). The other two, due to Hedin and Lundqvist and to Ng, contain p-dependent terms beyond the X r approximation which are intended to represent correlation corrections in approximate fashion. Except for Xrll with a = 4, the models all yield J,(O) (the Compton profile peak) within 2 % of one another.Both X a j l ( z~~) and Hedin-Lundqvist J,(O) values are always larger (by 1-5 %) than those generated from correlated wavefunctions, and the profiles produced from those models in general do not differ by more than about one per cent. The J,(O) values from Ng's model exhibit no obvious regularity in their relation to the correlated wavefunction results. Compared with correlated wavefunction q = 0 values. (ie J~"de'(0)/J~'"(O)), Xr/l(r.,) gives the smallest standard deviation over the five atoms tested: the same is true relative to q = 0 values from Hartree-Fock wavefunctions.

HTS Josephson plasma oscillator

“…When several branches were traced out, it appeared sequentially. These emissions are qualitatively different from conventional Josephson self-emission and are quite similar to those observed by tunnel injection of quasiparticles into YBCO, EBCO and BSCCO films given above [6][7][8] and are considered to be the incoherent plasmon emission arising from the electron-plasmon interaction. The emission of plasmons leads to microwave emission into free space.…”

“…The results for microwave emissions detected at 11.6-47 GHz were qualitatively similar among YBCO, EBCO and BSCCO samples. Figure 3 and 4 show typical results for the microwave emissions from quasiparticleinjected YBCO [6,7] and BSCCO [12] films, respectively, at the receiver frequency 47 GHz at different temperatures. At low temperatures (T = 4.2 K-10 K), the detected power increased almost linearly with increasing injection current, not being proportional to the injected power, suggesting the incoherent emission of microwaves.…”

“…Curves B 1 and B 2 correspond to the relatively weak injection case for which the Josephson plasma peak is clear, while curves C 1 and C 2 correspond to the strong injection case for which it is washed away. Experimentally, several reports suggesting Josephson plasma emission appeared quite recently [6][7][8][9][10][11][12]. The intensive quasiparticle injection into a c-axis oriented YBCO film induced a broad range of microwave emissions, while that into the c-axis direction of a BSCCO crystal induced both broadband and sharp nonequilibrium emissions.…”

“…We here present a brief review of these novel microwave emissions from a quasiparticle-injected nonequilibrium high-T c superconductor observed recently [6][7][8][9][10][11][12]…”

Microwave oscillation from Bi2Sr2CaCu2Oyintrinsic Josephson junction arrays

“…Recently, it has been reported that when a high-T c superconductor/insulator/normal metal tunnel junction is biased at a finite current, broadband microwaves are emit-ted [7][8][9]. The observed phenomenon is quite different from the Josephson self-emission and has been considered as Josephson plasma emission.…”