Spontaneous currents in Josephson junctions between unconventional superconductors and d-wave qubits (Review)

Kolesnichenko, Yu. A.; Omelyanchouk, A. N.; Zagoskin, A. M.

doi:10.1063/1.1789112

Cited by 13 publications

(13 citation statements)

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“…The Josephson effect in superconducting weak links is one of the most suitable instruments for investigation of the symmetry of D( ) k . It has heen shown, for example, that current-phase relations j J ( ) j in unconventional superconductors are quite different for different models of D( ) k , and hence the study of the Josephson effect enables one to judge the applicability of different models to the novel superconductors [3].…”

Section: Pacs: 7450+rmentioning

confidence: 99%

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Josephson effect in a weak link between borocarbides

Kolesnichenko

Shevchenko

2005

Low Temperature Physics

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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. PACS: 74.50.+rDetermination of the symmetry of the order parameter D in novel unconventional superconductors is important for the development of modern physics of superconductivity because the dependence of D( ) k on the direction of the electron wave vector k on the Fermi surface determines all of the kinetic and thermodynamic characteristics of the superconductor. Calculation of the order parameter D( ) k is a fundamental problem and requires knowledge of the pairing potential. Some general information about D( ) k can be obtained from the symmetry of a normal state, i.e., according to the Landau theory of secon-order phase transitions [1], the order parameter transforms only accoding to irreducible representations of the symmetry group of the normal state (for review, see [2]). Nevertheless, symmetry considerations reserve for the order parameter considerable freedom in the selection of irreducible representation and its basis functions. Therefore in many papers authors consider different models of the order parameter, which are based on possible representations of crystallographic point groups. The subsequent comparison of theoretical results with experimental data makes it possible to choose between available models of the order parameter. The Josephson effect in superconducting weak links is one of the most suitable instruments for investigation of the symmetry of D( ) k . It has heen shown, for example, that current-phase relations j J ( ) j in unconventional superconductors are quite different for different models of D( ) k , and hence the study of the Josephson effect enables one to judge the applicability of different models to the novel superconductors [3].Borocarbides, such as YNi 2 B 2 C and LuNi 2 B 2 C, exhibit unconventional superconductivity. There is strong evidence that in these materials the order parameter is highly anisotropic [4]. The order parameter in these compounds has fourfold symmetry, and there are deep minima along the [100] and [010] directions [4,5]. Both the symmetry of the borocarbide crystal structure and the experimental results have allowed the authors of Refs.[6] to suggest an s g + -wave model of the order parameter to describe the superconductivity in the borocarbides: J j is an alternating-sign quantity, which means that some reflected trajectories experience the intrinsic phase difference. This result in the suppression of the order parameter in the vicinity of the interface between two superconductors similar to what is known about the contact of two d-wave superconductors (see [7] and references therein); and in this case the non-self-consistent calculation, presented below, can be justified for the weak links in the form of both the point contact and the plane boundary between two banks. Another consequence of the intrinsic phase difference is th...

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Section: Pacs: 7450+rmentioning

confidence: 99%

“…Generally speaking, there is a current j y tangential to the boundary in addition to the current through the contact j x [3]. The case of the contact of two d-wave superconductors has heen considered in many papers (see [7] and references therein).…”

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Josephson effect in a weak link between borocarbides

Kolesnichenko

Shevchenko

2005

Low Temperature Physics

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“…Using superconducting quantum-interference devices (SQUID), Josephson junctions [8] show results which are consistent with 2 2 x y d − -wave symmetry of the pair potentials. Josephson junctions are building elements of many electronic and electromagnetic mesoscopic structures, which are proved to be promising elements of superconducting classical and quantum circuits [9,10]. In particular, junctions consisting of superconducting and ferromagnetic materials have been widely used as novel functional devices [11].…”

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confidence: 99%

Josephson current in d-wave superconductor junctions with ferromagnetic insulator

Yan-hua

Yang

et al. 2012

Low Temperature Physics

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We investigate the temperature dependence of the critical current and current-phase relation by taking into account the ferromagnetic scattering effect at interface in a d-wave superconductor (S)/ferromagnetic insulator layer (FI)/d-wave superconductor (S) junction. It is shown that both the barrier scattering and the roughness scattering at the interface always suppress the Andreev reflection. The Josephson critical currents depend to a great extent on the effective exchange field of the interface and the crystal orientation of the d-wave superconductor. The exchange field can lead to the change of the junction from 0 to π states and the alteration of the oscillation periods. It can also enhance the Josephson critical current in the junction under certain conditions.

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“…Josephson junctions between d -wave superconductors attract interest from the standpoint of realization of qubits, basic units of quantum computers (see e.g. 10 ). The situation considered here,with preset transport currents in the banks of the single-and double-point contacts, offers the possibility to control the spontaneous bistable states in a system of d -wave qubits.…”

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