923 research outputs found
Bloch inductance in small-capacitance Josephson junctions
We show that the electrical impedance of a small-capacitance Josephson
junction includes besides the capacitive term also an inductive
term . Similar to the known Bloch capacitance , the Bloch
inductance also depends periodically on the quasicharge , and its
maximum value achieved at always exceeds the value of
the Josephson inductance of this junction at fixed . The
effect of the Bloch inductance on the dynamics of a single junction and a
one-dimensional array is described.Comment: 5 pages incl. 3 fig
A hybrid superconductor-normal metal electron trap as a photon detector
A single-electron trap built with two Superconductor (S) - Insulator (I) -
Normal (N) metal tunnel junctions and coupled to a readout SINIS-type
single-electron transistor A (SET A) was studied in a photon detection regime.
As a source of photon irradiation, we used an operating second SINIS-type SET B
positioned in the vicinity of the trap. In the experiment, the average hold
time of the trap was found to be critically dependent on the voltage across SET
B. Starting in a certain voltage range, a photon-assisted electron escape was
observed at a rate roughly proportional to the emission rate of the photons
with energies exceeding the superconducting gap of S-electrodes in the trap.
The discussed mechanism of photon emission and detection is of interest for
low-temperature noise spectrometry and it can be of relevance for the ampere
standard based on hybrid SINIS turnstiles.Comment: submitted, 3 pages, 3 figure
Cooper pair cotunneling in single charge transistors with dissipative electromagnetic environment
We observed current-voltage characteristics of superconducting single charge
transistors with on-chip resistors of R about R_Q = h/4e^2 = 6.45 kOhm, which
are explained in terms of Cooper-pair cotunneling. Both the effective strength
of Josephson coupling and the cotunneling current are modulated by the
gate-induced charge on the transistor island. For increasing values of the
resistance R we found the Cooper pair current at small transport voltages to be
dramatically suppressed.Comment: 4 pages and 2 figure
Josephson tunnel junctions with nonlinear damping for RSFQ-qubit circuit applications
We demonstrate that shunting of Superconductor-Insulator-Superconductor
Josephson junctions by Superconductor-Insulator-Normal metal (S-I-N) structures
having pronounced non-linear I-V characteristics can remarkably modify the
Josephson dynamics. In the regime of Josephson generation the phase behaves as
an overdamped coordinate, while in the superconducting state the damping and
current noise are strikingly small, that is vitally important for application
of such junctions for readout and control of Josephson qubits. Superconducting
Nb/AlO/Nb junction shunted by Nb/AlO/AuPd junction of S-I-N type
was fabricated and, in agreement with our model, exhibited non-hysteretic I-V
characteristics at temperatures down to at least 1.4 K.Comment: 4 pages incl. 3 figure
Aluminum Single Electron Transistors with Islands Isolated from a Substrate
The low-frequency noise figures of single-electron transistors
(electrometers) of traditional planar and new stacked geometry were compared.
We observed a correlation between the charge noise and the contact area of the
transistor island with a dielectric substrate in the set of Al transistors
located on the same chip and having almost similar electric parameters. We have
found that the smaller the contact area the lower the noise level of the
transistor. The lowest noise value 8*10E-6 e/sqrt(Hz) at f = 10 Hz. has been
measured in a stacked transistor with an island which was completely isolated
from a substrate. Our measurements have unambiguously indicated that the
dominant source of the background charge fluctuations is associated with a
dielectric substrateComment: Review paper, latex, 10 pages, 7 figures, to be publ. in JLTP, 2000;
Proceeding of "Electron Transport in Mesoscopic Systems", August 12-15, 1999
Geteborg, Sweden, http://fy.chalmers.se/meso_satellite/index.html See also
LT22 manuscript: http://lt22.hut.fi/cgi/view?id=S1113
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