63 research outputs found
Two-junction superconductor-normal metal single-electron trap in a combined on-chip RC environment
Dissipative properties of the electromagnetic environment as well as on-chip
RC filtering are shown to suppress random state switchings in the two-junction
superconductor(S) - normal metal(N) electron trap. In our experiments, a local
high-ohmic resistor increased the hold time of the trap by up to two orders of
magnitude. A strong effect of on-chip noise filtering was observed for
different on-chip geometries. The obtained results are promising for
realization of the current standard on the basis of the S-N hybrid turnstile.Comment: 4 pages 3 figures LT2
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
Storage capabilities of a 4-junction single electron trap with an on-chip resistor
We report on the operation of a single electron trap comprising a chain of
four Al/AlOx/Al tunnel junctions attached, at one side, to a memory island and,
at the other side, to a miniature on-chip Cr resistor R=50 kOhm which served to
suppress cotunneling. At appropriate voltage bias the bi-stable states of the
trap, with the charges differing by the elementary charge e, were realized. At
low temperature, spontaneous switching between these states was found to be
infrequent. For instance, at T=70 mK the system was capable of holding an
electron for more than 2 hours, this time being limited by the time of the
measurement.Comment: 3 pages of text and 2 figure
The single electron R-pump: first experiment
We fabricated and tested the single electron R-pump, i.e. a three-junction Al
circuit with on-chip Cr resistors. We show that due to the presence of the
resistors (R > h/e^2 = 25.8 kOhm), the accuracy of electron transfer in the
R-pump can approach the level of 10^-8. Preliminary results of experiment with
the R-pump made at PTB are reported.Comment: 2 pages, incl. 3 figure
Superconducting Electrometer Based on the Resistively Shunted Bloch Transistor
We have fabricated the Bloch transistor shunted on-chip by a small-sized Cr
resistor with Rs about 1 kOhm. The Bloch transistor normally consists of two
small Josephson junctions connected in series, which in our case have been
replaced by two superconducting interferometer loops, each with two junctions
in parallel. A capacitively coupled gate is supplied to control the induced
charge of the small intermediate electrode (island) of the transistor. The
measured I-V curves show no hysteresis and correspond to the operation of a
effective Josephson junction at the high-damping and strong-noise limits. The
critical current of the system was found to be close to its nominal value, that
is in accordance with the electromagnetic environment theory. The I-V curves
were modulated by the gate with a period of e and a maximum swing of about 2
/mu_V. Such rather moderate modulation results from the Josephson-to- charging
energies ratio, Ej/Ec about 9, in our sample being far from its optimum value
of 0.3 up to 1.Comment: To be published in IEEE Transactions on Applied Superconductivity,
June 199
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