509 research outputs found
A low-noise series-array Josephson junction parametric amplifier
We have obtained parametric gain at 19 GHz from a distributed Josephson junction parametric amplifier whose active gain medium consists of a series array of 1000 Josephson junctions embedded in a coplanar waveguide. When cooled to 1.7 K the amplifier provides 16 dB gain in a mode where the internally generated double sideband noise referred to input is 0.5 ± 0.1 K. This noise is consistent with Nyquist noise generated from the losses. An instantaneous bandwidth of 125 MHz has been observed with a peak gain of 12 dB. The 3 dB compression point with a peak gain of 14.6 dB is -90.5 dB and the dynamic range is 38 dB
Avoided Antiferromagnetic Order and Quantum Critical Point in CeCoIn
We measured specific heat and resistivity of heavy fermion CeCoIn5 between
the superconducting critical field and 9 T, with field in the
[001] direction, and at temperatures down to 50mK. At 5T the data show Non
Fermi Liquid behavior down to the lowest temperatures. At field above 8T the
data exhibit crossover from the Fermi liquid to a Non Fermi Liquid behavior. We
analyzed the scaling properties of the specific heat, and compared both
resistivity and the specific heat with the predictions of a spin-fluctuation
theory. Our analysis leads us to suggest that the NFL behavior is due to
incipient antiferromagnetism (AF) in CeCoIn5, with the quantum critical point
in the vicinity of the . Below the AF phase which competes
with the paramagnetic ground state is superseded by the superconducting
transition.Comment: 5 pages, 3 figure
Theory of the Transition at 0.2 K in Ni-doped Bi2Sr2CaCu2O8
A theory is put forward that the electronic phase transition at 0.2 K in
Ni-doped BiSrCaCuO is result of the formation of a spin
density wave in the system of Ni impurities. The driving force for the
transition is the exchange interaction between the impurity spins and the spins
of the conduction electrons. This creates a small gap at two of the four nodes
of the superconducting gap. The effect is to reduce the thermal conductivity by
a factor of two, as observed.Comment: 10 pages and 1 figur
Thermal-Hall conductivity and long-lived quasiparticles in CeCoIn
In CeCoIn, the thermal conductivity and Hall conductivity
below display large anomalies below . The strong
suppression of the anomalies in weak fields implies the existence of long-lived
quasiparticles. We also discuss briefly the Wiedemann-Franz ratio and the
existence of a strongly field-dependent spin-fluctuation heat current.Comment: 2 pages, 2 figures, proceedings of M2S-HTSC-VIII, Dresden 200
The use of fitness testing to predict occupational performance in tactical personnel:Â A critical review
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