Stationary Josephson current in junctions involving d-wave superconductors with charge density waves: the temperature dependence and deviations from the law of corresponding states (original) (raw)
Related papers
Stationary Josephson Effect in Junctions Made of d-Wave Superconductors with Charge Density Waves
Dependences of the stationary Josephson current in symmetric and nonsymmetric tunnel junctions involving d-wave superconductors with charge density waves (CDWs) on the system parameters were calculated. Both the checkerboard and unidirectional CDW patterns were studied. The directionality of tunneling was taken into account. It was shown that CDWs can drastically influence the Josephson current, the changes being more significant in underdoped compositions. Металлофиз. новейшие технол. / Metallofiz. Noveishie Tekhnol. 2013, т. 35, № 4, сс. 1001-1015 Оттиски доступны непосредственно от издателя Фотокопирование разрешено только в соответствии с лицензией 2013 ИМФ (Институт металлофизики им. Г. В. Курдюмова НАН Украины) Напечатано в Украине. 1002 ALEXANDER M. GABOVICH, MAI SUAN LI, HENRYK SZYMCZAK
Low Temperature Physics, 2014
Stationary Josephson current I_c between d-wave superconductors was calculated for superconductor– insulator–superconductor structures with various rotations of crystals relatively to each other and the junction plane. The directionality of tunneling was taken into account. It was demonstrated that the temperature, T, dependences of I_c can become nonmonotonic for certain electrode orientations due to the T-dependent ratio between the contributions of positive and negative I_c components. This model gives an explanation to the effect observed in junctions involving cuprates and is an alternative to the well-known scenario that makes allowance for Andreev–Saint–James zero-energy levels.
ac Josephson effect in superconducting d -wave junctions
Physical Review B, 1999
We study theoretically the ac Josephson effect in superconducting planar d-wave junctions. The insulating barrier assumed to be present between the two superconductors may have arbitrary strength. Many properties of this system depend on the orientation of the d-wave superconductor: we calculate the ac components of the Josephson current. In some arrangements there is substantial negative differential conductance due to the presence of mid-gap states. We study how robust these features are to finite temperature and also comment on how the calculated current-voltage curves compare with experiments. For some other configurations (for small barrier strength) we find zero-bias conductance peaks due to multiple Andreev reflections through midgap states. Moreover, the odd ac components are strongly suppressed and even absent in some arrangements. This absence will lead to a doubling of the Josephson frequency. All these features are due to the d-wave order parameter changing sign when rotated 90 • . Recently, there have been several theoretical reports on parallel current in the d-wave case for both the stationary Josephson junction and for the normal metal-superconductor junction. Also in our case there may appear current density parallel to the junction, and we present a few examples when this takes place. Finally, we give a fairly complete account of the method used and also discuss how numerical calculations should be performed in order to produce current-voltage curves.
Nonstationary Josephson effect for superconductors with charge-density waves
Physical Review B, 1999
The nonstationary Josephson I 1 , interference I 2 , and quasiparticle J currents through symmmetrical and nonsymmetrical tunnel junctions involving superconductors with charge-density waves ͑CDW's͒ were calculated. In the symmetrical (s) case the voltage V dependence of the Josephson current I s 1 (V) has logarithmic singularities at ͉eV͉ϭ2⌬, ⌬ϩD, and 2D, where Dϭͱ(⌬ 2 ϩ⌺ 2 ), ⌬ is the superconducting order parameter, ⌺ is the dielectric order parameter, and e is the elementary charge. For temperatures T 0 the jump at a bias ͉eV͉ϭDϪ⌬ emerges in I s 1 (V). The I s 2 (V) and J s (V) possess jumps and singularities at the same biases where singularities and jumps occur in I s 1 (V). For the nonsymmetrical ͑ns͒ junctions, which include also the ordinary superconductor, singularities and jumps appear at biases ͉eV͉ϭDϩ⌬ BCS , ⌬ ϩ⌬ BCS , and ͑for T 0) ͉DϪ⌬ BCS ͉ and ͉⌬Ϫ⌬ BCS ͉. Here ⌬ BCS is the superconducting order parameter of the ordinary superconductor. The quasiparticle current J ns is an asymmetrical function of the voltage V and depends on the sign of ⌺. The theory describes the properties of NbSe 3 and high-T c oxides.
Physical Review B, v. 92, N 5, 054512, 2015
Quasiparticle tunnel current either between identical d-wave superconductors partially gapped by charge density waves (SCDWs) or between an SCDW and a normal metal was calculated. The cases of unidirectional and checkerboard CDWs were considered. The tunnel conductance was found in both cases to possess a number of peculiarities, which cannot be described by introducing a single combined gap. The results are in qualitative agreement with experimental data obtained for a number of cuprates by the scanning tunnel spectroscopy, intrinsic tunneling, and break-junction measurements. The difference between the experiment and the theory seems to stem from the spread of gap values occurring due to the intrinsic spatial inhomogeneity of nonstoichiometric oxides and reflected in the cuprate tunnel spectra.
The quasiparticle tunnel current J(V) between the superconducting ab-planes along the c-axis and the corresponding conductance G(V) = dJ /dV were calculated for symmetric junctions composed of disordered d-wave layered superconductors partially gapped by charge density waves (CDWs). Here, V is the voltage. Both the checkerboard and unidirectional CDWs were considered. It was shown that the spatial spread of the CDW-pairing strength substantially smears the peculiarities of G(V) appropriate to uniform superconductors. The resulting curves G(V) become very similar to those observed for a number of cuprates in intrinsic junctions, e.g. mesas. In particular, the influence of CDWs may explain the peak-dip-hump structures frequently found for high-Tc oxides.
Physical Review B, 2013
The theory of the stationary Josephson tunnel current I c was devised for junctions involving superconductors partially gapped by biaxial or unidirectional charge density waves (CDWs) and possessing a superconducting order parameter of d-wave symmetry. Specific calculations were carried out for symmetric junctions between two identical CDW superconducting electrodes and nonsymmetric ones composed of a CDW superconductor and a conventional isotropic s-wave superconductor. Two kinds of superconducting pairing symmetries were studied, namely, that appropriate to cuprates (d x 2 −y 2 ) and the d xy one. The corresponding calculations were also carried out for the extended s-wave symmetry of the superconducting order parameter. Allowances were made for the directionality of tunneling. In all the cases studied, the dependences of I c on the angle γ between the chosen crystal direction and the normal to the junction plane were found to be significantly influenced by CDWs. It was shown in particular that the d-wave driven periodicity of I c (γ ) in the CDW-free case is transformed into double-period beatings depending on the parameters of the system. The results of calculations testify that the orientation-dependent patterns I c (γ ) measured for CDW superconductors allow the CDW configuration (unidirectional or checkerboard) and the symmetry of superconducting order parameter to be determined. The predicted effects can be used to indirectly reveal CDWs in underdoped cuprates where pseudogaps are observed. The break-junction technique is an appropriate tool for this purpose.
Peculiarities of dc Josephson tunneling between d-wave superconductors with charge density waves
2012
Theory of stationary Josephson tunnel current Ic was built for junctions involving superconductors partially gapped by biaxial or unidirectional charge density waves (CDWs) and possessing a superconducting order parameter of d-wave symmetry. Specific calculations were carried out for symmetric junctions between two identical CDW superconducting electrodes and nonsymmetric ones composed of a CDW superconductor and a conventional isotropic s-wave superconductor. Two kinds of superconducting pairing symmetry were studied, namely, that appropriate to cuprates (dx2−y2) and the dxy-one. The corresponding calculations were also carried out for the extended s-wave symmetry of the superconducting order parameter. The directionality of tunneling was made allowance for. In all studied cases, the dependences of Ic on the angle γ between the chosen crystal direction and the normal to the junction plane were found to be significantly influenced by CDWs. It was shown, in particular, that the d-wav...