752 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
Nonequilibrium and Parity Effects in the Tunneling Conductance of Ultrasmall Superconducting Grains
Recent experiment on the tunneling spectra of ultrasmall superconducting
grains revealed an unusual structure of the lowest differential conductance
peak for grains in the odd charging states. We explain this behavior by
nonequilibrium ``gapless'' excitations associated with different energy levels
occupied by the unpaired electron. These excitations are generated by inelastic
cotunneling.Comment: 4 pages, 2 .eps figures include
Sensitivity and Linearity of Superconducting Radio-Frequency Single-Electron Transistors: Effects of Quantum Charge Fluctuations
We have investigated the effects of quantum fluctuations of quasiparticles on
the operation of superconducting radio-frequency single-electron transistors
(RF-SETs) for large values of the quasiparticle cotunneling parameter
, where and are the Josephson and charging
energies. We find that for , subgap RF-SET operation is still
feasible despite quantum fluctuations that renormalize the SET charging energy
and wash out quasiparticle tunneling thresholds. Surprisingly, such RF-SETs
show linearity and signal-to-noise ratio superior to those obtained when
quantum fluctuations are weak, while still demonstrating excellent charge
sensitivity.Comment: Submitted to Phys. Rev. Let
Resonant tunneling through a macroscopic charge state in a superconducting SET transistor
We predict theoretically and observe in experiment that the differential
conductance of a superconducting SET transistor exhibits a peak which is a
complete analogue in a macroscopic system of a standard resonant tunneling peak
associated with tunneling through a single quantum state. In particular, in a
symmetric transistor, the peak height is universal and equal to . Away from the resonance we clearly observe the co-tunneling current
which in contrast to the normal-metal transistor varies linearly with the bias
voltage.Comment: 11 pages, 3 figures, Fig. 1 available upon request from the first
autho
AC Josephson effect and resonant Cooper pair tunneling emission of a Cooper Pair Transistor
We measure the high-frequency emission of a single Cooper pair
transistor(SCPT) in the regime where transport is only due to tunneling of
Cooper pairs. This is achieved by coupling on-chip the SCPT to a
superconductor-insulator-superconductor junction and by measuring the photon
assisted tunneling current of quasiparticles across the junction. This
technique allows a direct detection of the AC Josephson effect of the SCPT and
provides evidence of Landau-Zener transitions for proper gate voltage. The
emission in the regime of resonant Cooper pair tunneling is also investigated.
It is interpreted in terms of transitions between charge states coupled by the
Josephson effect.Comment: Revtex4, 5 pages, 4 figures, final versio
FQHE interferometers in strong tunneling regime. The role of compactness of edge fields
We consider multiple-point tunneling in the interferometers formed between
edges of electron liquids with in general different filling factors in the
regime of the Fractional Quantum Hall effect (FQHE). We derive an effective
matrix Caldeira-Leggett models for the multiple tunneling contacts connected by
the chiral single-mode FQHE edges. It is shown that the compactness of the Wen-
Fr\"ohlich chiral boson fields describing the FQHE edge modes plays a crucial
role in eliminating the spurious non-locality of the electron transport
properties of the FQHE interferometers arising in the regime of strong
tunneling.Comment: 5 page
Resistively-shunted superconducting quantum point contacts
We have studied the Josephson dynamics of resistively-shunted ballistic
superconducting quantum point contacts at finite temperatures and arbitrary
number of conducting modes. Compared to the classical Josephson dynamics of
tunnel junctions, dynamics of quantum point contacts exhibits several new
features associated with temporal fluctuations of the Josephson potential
caused by fluctuations in the occupation of the current-carrying Andreev
levels.Comment: 5 pages, RevTex, 3 postscript figures include
Coulomb blockade in superconducting quantum point contacts
Amplitude of the Coulomb blockade oscillations is calculated for a
single-mode Josephson junction with arbitrary electron transparency . It is
shown that the Coulomb blockade is suppressed in ballistic junctions with . The suppression is described quantitatively as the Landau-Zener transition
in imaginary time.Comment: 5 pages, 3 figures include
Coulomb Charging Effects for Finite Channel Number
We consider quantum fluctuations of the charge on a small metallic grain
caused by virtual electron tunneling to a nearby electrode. The average
electron number and the effective charging energy are determined by means of
perturbation theory in the tunneling Hamiltonian. In particular we discuss the
dependence of charging effects on the number N of tunneling channels. Earlier
results for N>>1 are found to be approached rather rapidly with increasing N.Comment: 6 pages, 5 figure
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