共查询到20条相似文献,搜索用时 15 毫秒
1.
Direct observation of tunneling and nonlinear self-trapping in a single bosonic Josephson junction 总被引:1,自引:0,他引:1
Albiez M Gati R Fölling J Hunsmann S Cristiani M Oberthaler MK 《Physical review letters》2005,95(1):010402
We report on the first realization of a single bosonic Josephson junction, implemented by two weakly linked Bose-Einstein condensates in a double-well potential. In order to fully investigate the nonlinear tunneling dynamics we measure the density distribution in situ and deduce the evolution of the relative phase between the two condensates from interference fringes. Our results verify the predicted nonlinear generalization of tunneling oscillations in superconducting and superfluid Josephson junctions. Additionally, we confirm a novel nonlinear effect known as macroscopic quantum self-trapping, which leads to the inhibition of large amplitude tunneling oscillations. 相似文献
2.
We consider a combined nanomechanical-supercondcuting device that allows the Cooper pair tunneling to interfere with the mechanical motion of the middle superconducting island. Coupling of mechanical oscillations of a superconducting island between two superconducting leads to the electronic tunneling generates a supercurrent that is modulated by the oscillatory motion of the island. This coupling produces alternating finite and vanishing supercurrent as function of the superconducting phases. Current peaks are sensitive to the superconducting phase shifts relative to each other. The proposed device may be used to study the nanoelectromechanical coupling in case of superconducting electronics. 相似文献
3.
We consider the process of quantum tunneling between the superconducting and paramagnetic states of a nanometer-scale superconducting grain placed in a magnetic field. The grain is supposed to be weakly coupled to a normal metallic contact that plays the role of the spin reservoir. Using the instanton method, we find the probability of the quantum tunneling process and express it in terms of the applied magnetic field, order parameter of the superconducting grain, and conductance of the tunneling junction between the grain and metallic contact. 相似文献
4.
Sacépé B Chapelier C Marcenat C Kacmarcik J Klein T Bernard M Bustarret E 《Physical review letters》2006,96(9):097006
We present the first scanning tunneling spectroscopy study of single-crystalline boron-doped diamond. The measurements were performed below 100 mK with a low temperature scanning tunneling microscope. The tunneling density of states displays a clear superconducting gap. The temperature evolution of the order parameter follows the weak-coupling BCS law with Delta(0)/kBTc approximately 1.74. Vortex imaging at low magnetic field also reveals localized states inside the vortex core that are unexpected for such a dirty superconductor. 相似文献
5.
Laser probing of atomic Cooper pairs 总被引:1,自引:0,他引:1
We consider a gas of attractively interacting cold fermionic atoms which are manipulated by laser light. The laser induces a transition from an internal state with large negative scattering length to one with almost no interactions. The process can be viewed as a tunneling of atomic population between the superconducting and the normal states of the gas. It can be used to detect the BCS ground state and to measure the superconducting order parameter. 相似文献
6.
Resonant tunneling processes are studied in superconducting junctions of low transparency with the order parameter of the electrodes of different symmetry. A general equation of the resonant current is derived within the Green’s function formalism for the junctions of arbitrary dimensionality. The phase dependence of the supercurrent averaged over the set of localized states is analyzed for superconducting junctions with an isotropic order parameter. A numerical analysis of the resonant current transport in junctions with high-T c superconducting electrodes with the d symmetry of the order parameter was carried out. 相似文献
7.
《Physics letters. A》1988,131(2):125-130
We calculate the current-voltage characteristics of a small capacitance underdamped superconducting tunnel junction and find the value of the critical current which corresponds to switching between coherent voltage oscillations and uncorrelated single electron tunneling. Both Zener tunneling and dissipative relaxation are important in this context. 相似文献
8.
《Superlattices and Microstructures》1999,25(5-6):1067-1074
Using the scattering theory for superconductive tunneling systems, we formulate a theory for the dc current in a superconducting junction with unconventional anisotropic pairing symmetry. We find that the phase anisotropy of the unconventional superconductor has important effects on the quasi-particle dc tunneling current, leading to an effective phase-anisotropy-dependent order parameter and a strong abnormal current peak in the subgap structure of the tunneling current. 相似文献
9.
We report superconducting phase-periodic conductance oscillations in ferromagnetic wires with interfaces to conventional superconductors. The ferromagnetic wires were made of Ho, a conical ferromagnet. The distance between the interfaces was much larger than the singlet superconducting penetration depth. We explain the observed oscillations as due to the long-range penetration of an unusual helical triplet component of the order parameter that is generated at the superconductor/ferromagnet interfaces and maintained by the intrinsic rotating magnetization of Ho. 相似文献
10.
N. d''Ambrumenil 《Solid State Communications》1984,50(12):1043-1045
It is shown that the scanning tunneling microscope as developed by Binnig and Rohrer can be expected to resolve the spatial variations of the superconducting order parameter in inhomogeneous superconductors. 相似文献
11.
A new class of superconducting molecular intercalation complexes has been discovered in which paramagnetic molecules reside between metallic dichalcogenide layers six Angstroms thick. Interlayer coupling of the order parameter by Josephson tunneling appears unlikely. 相似文献
12.
We study theoretically a strongly type-II s-wave superconducting state of two-dimensional Dirac fermions in proximity to a ferromagnet having in-plane magnetization. It is shown that a magnetic domain wall can host a chain of equally spaced vortices in the superconducting order parameter, each of which binds a Majorana-fermion state. The overlap integral of neighboring Majorana states is sensitive to the position of the chemical potential of the Dirac fermions. Thermal transport and scanning tunneling microscopy experiments to probe the Majorana fermions are discussed. 相似文献
13.
H. Jirari R. Mélin N. Stefanakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):125-139
We consider the proximity effect in multiterminal ferromagnet/superconductor (FSF) hybrid structures in which two or three
electrodes are connected to a superconductor. We show that two competing effects take place in these systems: (i) pair breaking
effects due to the response to the exchange field induced in the superconductor; (ii) a reduction of the superconducting order
parameter at the interface that takes place already in NS junctions. We focus on this second effect that dominates if the
thickness of the S layer is small enough. We consider several single-channel electrodes connected to the same site. We calculate
the superconducting order parameter and the local density of state (LDOS). With two ferromagnetic electrodes connected to
a superconductor we find that the superconducting order parameter in the ferromagnetic alignment is larger than the superconducting
order parameter in the antiferromagnetic alignment ( > ), in agreement with [Eur. Phys. J. B 25, 373 (2002)]. If a third spin polarized electrode is connected to a superconductor we find that - can change sign as the transparency of the third electrode increases. This can be understood from the fact that the superconducting
order parameter is reduced if pair correlations among the ferromagnetic electrodes increase. If the two ferromagnetic electrodes
are within a finite distance we find Friedel oscillations in the Gorkov function but we still obtain > . 相似文献
14.
I. A. Devyatov M. Yu. Kupriyanov 《Journal of Experimental and Theoretical Physics》1997,85(1):189-194
The Josephson tunneling current in S-I-S structures where the main current transport channel is resonant tunneling through
an isolated localized state is calculated using the Bogolyubov-de Gennes equations. It is shown that the efficiency of equilibrium
Josephson resonant tunneling is determined only by the ratio of the width of the resonance level to the absolute value of
the order parameter for the superconducting electrodes with arbitrary relationships among the system parameters.
Zh. éksp. Teor. Fiz. 112, 342–352 (July 1997) 相似文献
15.
A theory of the de Haas-van Alphen effect in type-II superconductors is proposed. The effect of the electron scattering by
nonmagnetic impurities in a magnetic field in the potential produced by a nonuniform distribution of the order parameter in
a mixed state is investigated. The magnitude of the order parameter and quasiparticle density of states are determined from
the solution of the system of Gor’kov equations. It is shown that in the presence of even a small amount of impurities, the
superconducting state near the upper critical field is gapless. In this region, the oscillatory (in the magnetic field) contribution
to the density of states and the characteristic damping of the amplitude of the magnetization oscillations in the superconducting
state are found.
Zh. éksp. Teor. Fiz. 112, 1873–1892 (November 1997) 相似文献
16.
J. Bar-Sagi 《Solid State Communications》1978,27(4):363-365
The reflectivity of the superconducting-normal metal interface is calculated including the effect of variation of the order parameter in the superconducting layer. Application is made for Rowell and Tomasch oscillations amplitudes and thermal conductivity of type I superconductor in its intermediate state. 相似文献
17.
Priyadarshini Kapri Saurabh Basu 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(1):12
The tunneling conductance for a device consisting of a metal–insulator–superconductor (MIS) junction is studied in presence of Rashba spin–orbit coupling (RSOC) via an extended Blonder–Tinkham–Klapwijk formalism. We find that the tunneling conductance as a function of an effective barrier potential that defines the insulating layer and lies intermediate to the metallic and superconducting electrodes, displays an oscillatory behavior. The tunneling conductance shows high sensitivity to the RSOC for certain ranges of this potential, while it is insensitive to the RSOC for others. Additionally, when the period of oscillations is an odd multiple of a certain value of the effective potential, the conductance spectrum as a function of the biasing energy demonstrates a contrasting trend with RSOC, compared to when it is not an odd multiple. The explanations for the observation can be found in terms of a competition between the normal and Andreev reflections. Similar oscillatory behavior of the conductance spectrum is also seen for other superconducting pairing symmetries, thereby emphasizing that the insulating layer plays a decisive role in the conductance oscillations of a MIS junction. For a tunable Rashba coupling, the current flowing through the junction can be controlled with precision. 相似文献
18.
Sun Guoya Xing D.Y. Shen R. Lin H.Q. 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):33-38
The Nambu spinor Green's function approach is applied to calculating the density of states (DOS) and superconducting order
parameter in normal-metal/insulator/ferromagnet/superconductor (NM/I/FM/SC) junctions. It is found that the s-wave superconductivity and ferromagnetism can coexist near the FM/SC interface, which is induced by proximity effect. On
the SC side, the spin-dependent DOS appears both within and without the energy gap. On the FM side, the superconducting order
parameter displays a damped oscillation and the DOS exhibits some superconducting behavior. The calculated result for the
DOS in FM for “0 state” and “π state” can reproduce recent tunneling spectra in Al/Al2O3/PdNi/Nb tunnel junctions.
Received 1st July 2002 Published online 19 November 2002 相似文献
19.
M. Huth M. Jourdan H. Adrian 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):695-699
The node structure of the superconducting order parameter of the heavy-fermion system is analyzed within the weak-coupling theory. A pairing interaction induced by the exchange of antiferromagnetic spin excitations
is assumed as suggested by recent inelastic neutron scattering experiments and tunneling spectroscopy. The multi-sheeted Fermi
surface is taken into account. Based on a model susceptibility for the simple antiferromagnetic structure of , line nodes result at the rim of the magnetic Brillouin zone.
Received 29 July 1999 相似文献
20.
It is observed that doping suppresses the long range anti-ferromagnetic order and induces superconducting phase for a suitable doping. In order to study this effect, we present a model study of the doping dependence of the tunneling conductance in high-Tc systems. The system is described by the Hamiltonian consisting of spin density wave (SDW) and s-wave type superconducting interaction in presence of varying impurity concentrations. The gap equations are calculated by using Green’s functions technique of Zubarev. The gap equations and the chemical potential are solved self-consistently. The imaginary part of the electron Green’s functions shows the quasi-particle density of states which represent the tunneling conductance observed by the scanning tunneling microscopy (STM). We investigate the effect of impurity on the gap equations as well as on the tunneling conductance. The results will be discussed based on the experimental observations. 相似文献