Search results for " superconductivity"
showing 10 items of 319 documents
INFLUENCE OF LENGTH ON THE NOISE DELAYED SWITCHING OF LONG JOSEPHSON JUNCTIONS
2008
The transient dynamics of long overlap Josephson junctions in the frame of the sine-Gordon model with a white noise source is investigated. The effect of noise delayed decay is observed for the case of overdamped sine-Gordon equation. It is shown that this noise induced effect, in the range of small noise intensities, vanishes for junctions lengths greater than several Josephson penetration length.
Interaction-free measurements with superconducting qubits
2008
An interaction-free measurement protocol is described for a quantum circuit consisting of a superconducting qubit and a read-out Josephson junction. By measuring the state of the qubit one can ascertain the presence of a current pulse through the circuit at a previous time without any energy exchange between the qubit and the pulse.
Running-phase state in a Josephson washboard potential
2005
We investigate the dynamics of the phase variable of an ideal underdamped Josephson junction in switching current experiments. These experiments have provided the first evidence for macroscopic quantum tunneling in large Josephson junctions and are currently used for state read-out of superconducting qubits. We calculate the shape of the resulting macroscopic wavepacket and find that the propagation of the wavepacket long enough after a switching event leads to an average voltage increasing linearly with time.
Voltage drop across Josephson junctions for L\'evy noise detection
2020
We propose to characterize L\'evy-distributed stochastic fluctuations through the measurement of the average voltage drop across a current-biased Josephson junction. We show that the noise induced switching process in the Josephson washboard potential can be exploited to reveal and characterize L\'evy fluctuations, also if embedded in a thermal noisy background. The measurement of the average voltage drop as a function of the noise intensity allows to infer the value of the stability index that characterizes L\'evy-distributed fluctuations. An analytical estimate of the average velocity in the case of a L\'evy-driven escape process from a metastable state well agrees with the numerical calc…
Investigations on the c-axis transport properties of YBa/sub 2/Cu/sub 3/O/sub 7-δ//PrBa/sub 2/Cu/sub 3/O/sub 7-δ/ thin film superlattices
1997
In this paper we report on the c-axis transport properties of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta///PrBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// superlattices. We describe the preparation, characterisation and patterning of thin film superlattices into suitable mesa structures via standard photolithography. Resistive measurements were carried out which point towards an inhomogenous current distribution in the normal state resistance. Below T/sub c/, the c-axis properties determine the temperature dependent resistance. Resonant tunneling is observed with no Josephson current.
Induced unconventional superconductivity on the surface states of Bi2Te3 topological insulator
2017
Topological superconductivity is central to a variety of novel phenomena involving the interplay between topologically ordered phases and broken-symmetry states. The key ingredient is an unconventional order parameter, with an orbital component containing a chiral $p_x$ + i$p_y$ wave term. Here we present phase-sensitive measurements, based on the quantum interference in nanoscale Josephson junctions, realized by using Bi$_2$Te$_3$ topological insulator. We demonstrate that the induced superconductivity is unconventional and consistent with a sign-changing order parameter, such as a chiral $p_x$ + i$p_y$ component. The magnetic field pattern of the junctions shows a dip at zero externally a…
Tunneling and point contact investigations of La1.85Sr0.15CuO4
1987
The high-T c superconductor La1.85Sr0.15CuO4 was investigated by means of point contact and tunneling measurements on small-sized contacts. We find different values for the energy gap at different points of the samples. The ratio 2Delta/k B T c ranges from about 3 to 6. For some point contacts we observe a clear signature of a supercurrent. Data for the temperature dependence of the critical current are presented.
Phase dynamics in graphene-based Josephson junctions in the presence of thermal and correlated fluctuations
2014
In this work we study by numerical methods the phase dynamics in ballistic graphene-based short Josephson junctions. The supercurrent through a graphene junction shows a non-sinusoidal phase-dependence, unlike a conventional junction ruled by the well-known d.c. Josephson relation. A superconductor-graphene-superconductor system exhibits superconductive quantum metastable states similar to those present in normal current-biased JJs. We explore the effects of thermal and correlated fluctuations on the escape time from these metastable states, when the system is stimulated by an oscillating bias current. As a first step, the analysis is carried out in the presence of an external Gaussian whit…
Spin torques and magnetic texture dynamics driven by the supercurrent in superconductor/ferromagnet structures
2018
We introduce the general formalism to describe spin torques induced by the supercurrents injected from the adjacent superconducting electrodes into the spin-textured ferromagnets. By considering the adiabatic limit for the equal-spin superconducting correlations in the ferromagnet we show that the supercurrent can generate both the field-like spin transfer torque and the spin-orbital torque. These dissipationless spin torques are expressed through the current-induced corrections to the effective field derived from the system energy. The general formalism is applied to show that the supercurrent can either shift or move the magnetic domain walls depending on their structure and the type of s…
Thermodynamics of a Phase-Driven Proximity Josephson Junction
2019
We study the thermodynamic properties of a superconductor/normal metal/superconductor Josephson junction {in the short limit}. Owing to the proximity effect, such a junction constitutes a thermodynamic system where {phase difference}, supercurrent, temperature and entropy are thermodynamical variables connected by equations of state. These allow conceiving quasi-static processes that we characterize in terms of heat and work exchanged. Finally, we combine such processes to construct a Josephson-based Otto and Stirling cycles. We study the related performance in both engine and refrigerator operating mode.