Searcharxiv⌕ Search

arXiv subjects

Yu. A. Kolesnichenko

Publications and source records attributed to Yu. A. Kolesnichenko.

At least 37 records · Page 2Linked to original sources
arXiv2009

Magneto-orientation and quantum size effect in SP-STM conductance in the presence of a subsurface magnetic cluster

The influence of a single magnetic cluster in a non-magnetic host metal on the spin current $\mathbf{j}^{(s)}$ and the charge current $\mathbf{j}$ in the vicinity of a ferromagnetic STM tip is studied theoretically. Spin-flip processes due to electron interaction with the cluster are taken into account. We show that quantum interference between the partial waves injected from the STM tip and those scattered by the cluster results in the appearance of components perpendicular to the initial polarization of the spin current $\mathbf{j}^{(s)}$, which obtain a strongly inhomogeneous spatial distribution. This interference produces oscillations of the conductance as a function of the distance between the contact and the cluster center. The oscillation amplitude depends on the current polarization. We predict a strong magneto-orientational effect: the conductance oscillations may grow, shrink, or even vanish for rotation of the cluster magnetic moment $\mathbfμ_{\mathrm{eff}}$ by an external magnetic field. These results can be used for the determination of the $ \mathbfμ_{\mathrm{eff}}$ for magnetic clusters below a metal surface.

cond-mat.mes-hall↗
arXiv2009

Spin polarized transport in the weak-link between $f$-wave superconductors

The spin current in the Josephson junction as a weak link (interface) between misorientated triplet superconductors is investigated theoretically for the models of the order parameter in $UPt_{3}$. Green functions of the system are obtained from the quasiclassical Eilenberger equations. The analytical results for the charge and spin currents are illustrated by numerical calculations for the certain misorientation angles of gap vector of superconductors. As the main result of this paper, it is found that, at some values of the phase difference, at which the charge current is exactly zero, the spin current has its maximum value. Furthermore, it is shown that the origin of spin current is the misorientation between gap vectors of triplet superconductors.

cond-mat.supr-con↗
arXiv2008

The effect of magnetic (phase) inhomogeneities upon the low temperature conductivity of antiferromagnetic La_{2}CuO_{4+δ} single crystal

It is found that a strong inhomogeneous distribution of oxygen in single crystal La_{2}CuO_{4+δ} can lead to the formation of isolated superconducting inclusions, the average hole concentration being no more than 0.0024 per Cu atom. The behavior of the conductivity in the magnetic field below T=20 K is consistent with possible existence of a insulating low-temperature magnetic phase (spin density waves), which is typical of cuprates with excess oxygen.

cond-mat.supr-con↗
arXiv2008

Influence of a single defect on the conductance of a tunnel point contact between a normal metal and a superconductor

We have investigated theoretically the conductance of a Normal-Superconductor point-contact in the tunnel limit and analyzed the quantum interference effects originating from the scattering of quasiparticles by point-like defects. Analytical expressions for the oscillatory dependence of the conductance on the position of the defect are obtained for the defect situated either in the normal metal, or in the superconductor. It is found that the amplitude of oscillations significantly increases when the applied bias approaches the gap energy of the superconductor. The spatial distribution of the order parameter near the surface in the presence of a defect is also obtained.

cond-mat.mes-hall↗
arXiv2008

The signature of subsurface Kondo impurities in the local tunnel current

The conductance of a tunnel point-contact in an STM-like geometry having a single defect placed below the surface is investigated theoretically. The effect of multiple electron scattering by the defect after reflections by the metal surface is taken into account. In the approximation of s-wave scattering the dependence of the conductance on the applied voltage and the position of the defect is obtained. The results are illustrated for a model s-wave phase shift describing Kondo-resonance scattering. We demonstrate that multiple electron scattering by the magnetic impurity plays a decisive role in the point-contact conductance at voltages near the Kondo resonance. We find that the sign and shape of the Kondo anomaly depends on the position of the defect.

cond-mat.mes-hall↗
arXiv2007

Conductance of a tunnel point-contact of noble metals in the presence of a single defect

In paper [1] (Avotina et al. Phys. Rev. B,74, 085411 (2006)) the effect of Fermi surface anisotropy to the conductance of a tunnel point contact, in the vicinity of which a single point-like defect is situated, has been investigated theoretically. The oscillatory dependence of the conductance on the distance between the contact and the defect has been found for a general Fermi surface geometry. In this paper we apply the method developed in [1] to the calculation of the conductance of noble metal contacts. An original algorithm, which enables the computation of the conductance for any parametrically given Fermi surface, is proposed. On this basis a pattern of the conductance oscillations, which can be observed by the method of scanning tunneling microscopy, is obtained for different orientations of the surface for the noble metals.

cond-mat.mes-hall↗
arXiv2007

Magneto-quantum oscillations of the conductance of a tunnel point-contact in the presence of a single defect

The influence of a quantizing magnetic field $H$ to the conductance of a tunnel point contact in the presence of the single defect has been considered. We demonstrate that the conductance exhibits specific magneto-quantum oscillations, the amplitude and period of which depend on the distance between the contact and the defect. We show that a non-monotonic dependence of the point-contact conductance results from a superposition of two types of oscillations: A short period oscillation arising from electron focusing by the field $H$ and a long period oscillation of Aharonov-Bohm-type originated from the magnetic flux passing through the closed trajectories of electrons moving from the contact to the defect and returning back to the contact.

cond-mat.mes-hall↗
arXiv2006

Signature of Fermi surface anisotropy in point contact conductance in the presence of defects

In a previous paper (Avotina et al.,Phys. Rev. B Vol.71, 115430 (2005)) we have shown that in principle it is possible to image the defect positions below a metal surface by means of a scanning tunnelling microscope. The principle relies on the interference of electron waves scattered on the defects, which give rise to small but measurable conductance fluctuations. Whereas in that work the band structure was assumed to be free-electron like, here we investigate the effects of Fermi surface anisotropy. We demonstrate that the amplitude and period of the conductance oscillations are determined by the local geometry of the Fermi surface. The signal results from those points for which the electron velocity is directed along the vector connecting the point contact to the defect. For a general Fermi surface geometry the position of the maximum amplitude of the conductance oscillations is not found for the tip directly above the defect. We have determined optimal conditions for determination of defect positions in metals with closed and open Fermi surfaces.

cond-mat.mes-hall↗
arXiv2005

Josephson effect in a weak link between borocarbides

A stationary Josephson effect is analyzed theoretically for a weak link between borocarbide superconductors. It is shown that different models of the order parameter result in qualitatively different current-phase relations.

cond-mat.supr-con↗
arXiv2005

Conductance of the elliptically shaped quantum wire

The conductance of a ballistic elliptically shaped quantum wire is investigated theoretically. It is shown that the effect of the curvature results in strong oscillating dependence of the conductance on the applied bias.

cond-mat.mes-hall↗
arXiv2005

Vortex-like current states in Josephson ballistic point contacts

The stationary Josephson effect is studied theoretically in the situation when there is externally injected transport supercurrent which flows in the banks parallel to the contact interface. Coexistence of this supercurrent with the order parameter phase difference between the banks of the contact results in the appearance of quasiparticles in the weak link, which create the current, localized in the vicinity of the contact and counter-flowing to the transport supercurrent. We review the results of our previous study of weak links between current-carrying conventional and unconventional (d-wave) superconductors. And further we study the weak link in the form of double point contact between current-carrying superconductors. The current distribution patterns, containing the vortex-like states, are obtained.

cond-mat.supr-con↗
arXiv2005

Stationary Josephson effect in a weak-link between nonunitary triplet superconductors

A stationary Josephson effect in a weak-link between misorientated nonunitary triplet superconductors is investigated theoretically. The non-self-consistent quasiclassical Eilenberger equation for this system has been solved analytically. As an application of this analytical calculation, the current-phase diagrams are plotted for the junction between two nonunitary bipolar $f-$wave superconducting banks. A spontaneous current parallel to the interface between superconductors has been observed. Also, the effect of misorientation between crystals on the Josephson and spontaneous currents is studied. Such experimental investigations of the current-phase diagrams can be used to test the pairing symmetry in the above-mentioned superconductors.

cond-mat.supr-con↗
arXiv2005

Transport of Charge and Spin in the Weak Link between Misoriented $PrOs_4Sb_{12}$ Superconductors

Recently, the ``$(p+h)-$wave'' form of pairing symmetry has been proposed for the superconductivity in $PrOs_{4}Sb_{12}$ compound [Parker D, Maki K and Haas S, \textbf{cond-mat/0407254}]. In the present paper, a stationary Josephson junction as a weak-link between $PrOs_{4}Sb_{12}$ triplet superconductors is theoretically investigated. The quasiclassical Eilenberger equations are analytically solved. The spin and charge current-phase diagrams are plotted and the effect of misorientation between crystals on the spin current, and spontaneous and Josephson currents is studied. It is found that such experimental investigations of the current-phase diagrams can be used to test the pairing symmetry in the above-mentioned superconductors. It is shown that this apparatus can be applied as a polarizer for the spin current.

cond-mat.supr-con↗
arXiv2005

Method to determine defect positions below a metal surface by STM

The oscillatory voltage dependence of the conductance of a quantum point contact in the presence of a single point-like defect has been analyzed theoretically. Such signals are detectable and may be exploited to obtain information on defect positions below a metal surface. Both tunnel junctions and ballistic contacts of adiabatic shape have been considered. The effect of quantum interference has been taking into account between the principal wave that is directly transmitted through the contact and the partial wave that is scattered by the contact and the defect. This effect leads to oscillations of the conductance as a function of applied voltage. We obtain the dependence of the period and amplitude of the conductance oscillations on the position of the defect inside the metal.

cond-mat.mes-hall↗
arXiv2004

Effect of point-contact transparency on coherent mixing of Josephson and transport supercurrents

The influence of electron reflection on dc Josephson effect in a ballistic point contact with transport current in the banks is considered theoretically. The effect of finite transparency on the vortex-like currents near the contact and at the phase difference $ϕ=π,$ which has been predicted recently \cite{KOSh}, is investigated. We show that at low temperatures even a small reflection on the contact destroys the mentioned vortex-like current states, which can be restored by increasing of the temperature.

cond-mat.supr-con↗
arXiv2003

Josephson and spontaneous currents at the interface between two d-wave superconductors with transport current in the banks

A stationary Josephson effect in the ballistic contact of two d-wave superconductors with different axes orientation and with tangential transport current in the banks is considered theoretically. We study the influence of the transport current on the current-phase dependence for the Josephson and tangential currents at the interface. It is demonstrated that the spontaneous surface current at the interface depends on the transport current in the banks due to the interference of the angle-dependent current-carrying condensate wave functions of the two superconductors.

cond-mat.supr-con↗
arXiv2003

Nonlocal mixing of supercurrents in Josephson ballistic point contact

We study coherent current states in the mesoscopic superconducting weak link simultaneously subjected to the order parameter phase difference on the contact and to the tangential to the junction interface superfluid velocity in the banks. The Josephson current-phase relation controlled by the external transport current is obtained. At phase difference close to pi the nonlocal nature of the Josephson phase-dependent current results in the appearance of two vortexlike states in the vicinity of the contact.

cond-mat.supr-con↗