Helical order of spins in superconductors

Bulaevski, L.N.; Rusinov, A.I.; Kulić, Miodrag L.

doi:10.1016/0038-1098(79)91146-3

Cited by 66 publications

(14 citation statements)

References 4 publications

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“…One of the characteristic features in the superconducting phase is the mixing of the spin-singlet and spin-triplet Cooper pairing channels which are otherwise distinguished by parity [2]. This is likely responsible for the surprisingly high value of the upper critical field H c2 which exceeds the paramagnetic limit [3,6,8,11,12]. CePt 3 Si displays further intriguing properties.…”

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confidence: 99%

Nuclear magnetic relaxation rate in a noncentrosymmetric superconductor

et al. 2006

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For a noncentrosymmetric superconductor such as CePt3Si, we consider a Cooper pairing model with a two-component order parameter composed of spin-singlet and spin-triplet pairing components. We demonstrate that such a model on a qualitative level accounts for experimentally observed features of the temperature dependence of the nuclear spin-lattice relaxation rate T −1 1 , namely a peak just below Tc and a line-node gap behavior at low temperatures.Inversion symmetry is one of the key points for the formation of Cooper pairs in superconductors. Unusual properties arise in superconductors whose crystal structure does not possess an inversion center (e.g., Refs. [1,2,3,4,5], and references therein). The recent discovery of superconductivity in the noncentrosymmetric heavy Fermion compound CePt 3 Si has initiated much interest, as experimental data revealed various intriguing features [6,7,8]. The essential element in modelling noncentrosymmetric systems is the presence of antisymmetric spin-orbit coupling [9,10]. One of the characteristic features in the superconducting phase is the mixing of the spin-singlet and spin-triplet Cooper pairing channels which are otherwise distinguished by parity [2]. This is likely responsible for the surprisingly high value of the upper critical field H c2 which exceeds the paramagnetic limit [3,6,8,11,12]. CePt 3 Si displays further intriguing properties. Recent nuclear magnetic resonance (NMR) experiments found an overall anomalous temperature dependence of the nuclear spin-lattice relaxation rate T −1 1 [8,13,14]. The behavior of T −1 1 shows a (Hebel-Slichter) peak just below the superconducting critical temperature T c , and simultaneously a T 3 dependence at low temperatures indicating line nodes in the quasiparticle gap. Such a gap with line nodes is also suggested by measurements of the London penetration depth [8]. At first sight, those experimental results seem to be mutually contradicting, as the features of unconventional Cooper pairing (line nodes) and of conventional superconductivity (peak in T −1 1 due to the coherence effect) are implied at the same time by the temperature dependence of T −1 1 [8,13,14].In the present study, we demonstrate that these apparently conflicting behaviors can be reconciled by taking account of the mixing of the pairing channels with opposite parity, which naturally occurs in superconductors without inversion center. For this purpose, we consider a pairing model with a two-component order parameter consisting of spin-singlet and spin-triplet pairing components. Such a model contains the necessary ingredients to account for the observed features of T −1 1 , i.e., the linenode behavior at low temperatures and the coherence effect just below T c . At the same time, the pairing model would also explain the temperature dependence of the London penetration depth qualitatively and be consistent with earlier studies of H c2 [3,15].We base our analysis on a Hamiltonian considered in Ref. [3], in which the lack of inversion symmetry is incorporated ...

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confidence: 99%

Nuclear magnetic relaxation rate in a noncentrosymmetric superconductor

et al. 2006

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“…In clean superconductors the oscillatory magnetic order can give rise to the gapless quasiparticle spectrum 5,8,9 if h ex > ∆, what is just the case in TmNi 2 B 2 C where h ex > 60 K and ∆ < 20. The gapless region on the Fermi surface given by the condition Q · v F = 0.…”

Section: Gapless Superconductivitymentioning

confidence: 99%

“…A theory has been developed and the phase diagram was given in Refs. 5,8,9 where the possibility of the coexistence of S and spiral or domain-like magnetic order has been elaborated quantitatively by including the exchange (EX) and electromagnetic (EM) interaction of conduction electrons and localized magnetic moments (LM's). It has been also demonstrated that the theory based on the EM interaction only 10 can not describe the coexistence problem in real systems.…”

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confidence: 99%

Magnetism and superconductivity in (RE) Ni2B2C: The case of TmNi2B2C

1997

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The recently reported 1,2 coexistence of an oscillatory magnetic order with the wave vector Q = 0.241Å −1 and superconductivity in TmNi 2 B 2 C is analyzed theoretically. It is shown that the oscillatory magnetic order and superconductivity interact predominantly via the exchange interaction between localized moments (LM's) and conduction electrons, while the electromagnetic interaction between them is negligible. In the coexistence phase of the clean TmNi 2 B 2 C the quasiparticle spectrum should have a line of zeros at the Fermi surface, giving rise to the power law behavior of thermodynamic and transport properties. Two scenarios of the origin of the oscillatory magnetic order in TmNi 2 B 2 C are analyzed: a) due to superconductivity and b) independently on superconductivity. Experiments in magnetic field are proposed in order to choose between them.

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“…These functions for a magnetic superconductor (MS ) with a spiral structure have been obtained in Ref. [12]. In this case the functionsF depend on the center-of-mass coordinate and momentum direction so that the system is anisotropic.…”

Section: Introductionmentioning

confidence: 99%

“…[9] (see also Ref. [12]), and on the order of magnitude it is equal to l m ≈ 2π(ξ 0 k F ) 1/3 /k F , where k F is the Fermi momentum and ξ 0 = v F /π∆ 0 is the correlation length in a clean superconductor. For example, in HoMo 6 S 8 the wave vector of the periodic magnetic structure Q ≈ 0.03 A −1 [2,10,11].…”

Section: Introductionmentioning

confidence: 99%

Surface effects in magnetic superconductors with a spiral magnetic structure

Volkov

2008

Phys. Rev. B

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We consider a magnetic superconductor (MS ) with a spiral magnetic structure. On the basis of generalized Eilenberger and Usadel equations we show that near the boundary of the MS with an insulator or vacuum the condensate (Gor'kov's) Green's functions are disturbed by boundary conditions and differ essentially from their values in the bulk. Corrections to the bulk quasiclassical Green's functions oscillate with the period of the magnetic spiral, 2π/Q, and decay inside the superconductor over a length of the order v/2πT (ballistic limit) or D/πT (diffusive limit). We calculate the dc Josephson current in an MS/I/MS tunnel junction and show that the critical Josephson current differs substantially from that obtained with the help of the tunnel Hamiltonian method and bulk Green's functions.

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Helical order of spins in superconductors

Cited by 66 publications

References 4 publications

Nuclear magnetic relaxation rate in a noncentrosymmetric superconductor

Nuclear magnetic relaxation rate in a noncentrosymmetric superconductor

Magnetism and superconductivity in (RE) Ni2B2C: The case of TmNi2B2C

Surface effects in magnetic superconductors with a spiral magnetic structure

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