Spin-singlet superconductivity with a full gap in locally noncentrosymmetric SrPtAs

Matano, Kazuaki; Arima, Kazuya; Maeda, S.; Nishikubo, Yoshihiro; Kudo, Kazuhiro; Nohara, M.; 鄭, 国慶

doi:10.1103/physrevb.89.140504

Cited by 33 publications

(45 citation statements)

References 26 publications

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“…A coherence peak below T c and an exponential decay as temperature decreases were observed. 10 These results were interpreted in connection with an s-wave pairing symmetry with a gap 2∆ 0 = 3.85k B T c , a value relatively high compared to the BCS standard. More recently, spinlattice relaxation rate 1/T 1 of 75 As was measured in two different polycrystalline samples of SrPtAs.…”

Section: 4mentioning

confidence: 85%

High-resolution magnetic penetration depth and inhomogeneities in locally noncentrosymmetric SrPtAs

et al. 2016

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We present a magnetic penetration-depth study on polycrystalline and granular samples of SrPtAs, a pnictide superconductor with a hexagonal structure containing PtAs layers that individually break inversion symmetry (local noncentrosymmetry). Compact samples show a clearcut s-wave-type BCS behavior, which we consider to be the intrinsic penetration depth of SrPtAs. Granular samples display a sample-dependent second diamagnetic drop, attributed to the intergrain coupling. Our experimental results point to a nodeless isotropic superconducting energy gap in SrPtAs, which puts strong constraints on the driven mechanism for superconductivity and the order parameter symmetry of this compound.

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Section: 4mentioning

confidence: 85%

High-resolution magnetic penetration depth and inhomogeneities in locally noncentrosymmetric SrPtAs

et al. 2016

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“…Furthermore the f -wave pairing state is a triplet of the type √ 2(↑↓ + ↓↑). Therefore this state can not be excluded by a suppressed Knight-shift in the superconducting phase found by Matano et al 9 Indeed, in this compound, a Hebel-Slichter peak or a retardation of the decay in 1/T 1 T does not imply conventional s-wave superconductivity. Furthermore, to eliminate line nodes in the order parameter, a corresponding model is included.…”

Section: Nuclear Relaxation Ratementioning

confidence: 96%

“…Parallel to our work, Matano et al 9 performed NMR/NQR experiments on SrPtAs. While their 75 As T 1 relaxation data are consistent with ours with respect to the evidence for a fully gapped superconducting state.…”

Section: Introductionmentioning

confidence: 99%

Multigap superconductivity in locally noncentrosymmetric SrPtAs: AnAs75nuclear quadrupole resonance investigation

et al. 2014

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We report detailed 75 As-NQR investigations of the locally non-centrosymmetric superconductor SrPtAs. The spin-lattice relaxation studies prove weakly coupled multi-gap superconductivity. A retardation of the decay in 1/T1T evidences a nodeless (fully gapped) superconducting state on the complex multi-pocket Fermi surface, which is consistent with an anisotropic s-wave order parameter and with proposed unconventional f -wave and chiral d -wave symmetries. A quantitative analysis of these models favors the unconventional f -wave state.

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“…Therefore a detailed experimental investigation of QPI in SrPtAs should be able to discriminate between the theoretically proposed gap symmetries. This is particularly desirable because recent NMR and NQR experiments [4] suggest a fully gapped spin singlet state.…”

Section: After Inversionĝmentioning

confidence: 99%

“…The momentum dependence of these unconventional pair states was investigated theoretically by Goryo et al [3] and it was found that even A 1g , E g and odd A 2u states are viable candidates. However sofar there is only few experimental evidence to discriminate between them [4].…”

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confidence: 99%

Gap function of hexagonal pnictide superconductor SrPtAs from quasiparticle interference spectrum

Akbari

Thalmeier

2014

EPL

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-The pnictide superconductor SrPtAs has a hexagonal layered structure containing inversion symmetry. It is formed by stacking two inequivalent PtAs layers separated by Sr layers. The former have no local (in-plane) inversion symmetry and therefore a (layer-) staggered Rashba spin orbit coupling appears which splits the three Kramers degenerate bands into six quasi-2D bands. The symmetry of the superconducting state of SrPtAs is unknown. Three candidates, spinsinglet A1g and Eg as well as triplet A2u states have been proposed. We predict the quasiparticle interference (QPI) spectrum for these gap functions in t-matrix Born approximation. We show that distinct differences in the pattern of characteristic QPI wave vectors appear. These results may be important to determine the gap symmetry of SrPtAs by STM-QPI method.Transition metal pnictide superconductors (SC) in particular the Fe-based systems are all of the tetragonal (orthorhombic) structure. The layered Pt-pnictide SrPtAs [1] is the first superconductor (T c = 2.4 K) in that class with hexagonal structure composed of honeycomb Pt-As layers spaced by Sr layers. It may be viewed as a MgB 2 type structure with Mg sites ocuppied by Sr and B sites in an ordered fashion such that Pt-As alternate in the 2D honeycomb layers as well along the hexagonal c-axis. The resulting structure has an overall 3D inversion center whereas the individual layers lack 2D inversion symmetry which is not contained in the C 3v layer point group.Because the electronic states at the Fermi level are mostly of Pt(5d) type with strong spin orbit coupling this leads to a peculiar electronic band structure [2]. Firstly the two inequivalent Pt-As layers have only small interlayer hopping which results in a quasi-2D band structure consisting of three hole bands and associated Fermi surface (FS) columns. Secondly an effective 2D Rashba spin orbit coupling term leads to a large splitting of the three bands which depends on k z in such a way that overall 3D inversion symmetry is restored. This has consequences for the possible superconducting pair states. Due to essentially decoupled layers it is reasonable to assume only intra-layer pairing. Then one can expect features as in the non-centrosymmetric superconductors consisting of a mixture of spin-singlet and triplet pairing of the in-plane order parameter due to lack of local 2D inversion symmetry. For the overall 3D superconducting state even or odd parity classification is restored due to the two inequivalent Sr-Pt layers. The momentum dependence of these unconventional pair states was investigated theoretically by Goryo et al [3] and it was found that even A 1g , E g and odd A 2u states are viable candidates. However sofar there is only few experimental evidence to discriminate between them [4].One of the most powerful recent methods to determine the symmetry of the gap function is STM quasiparticle interference (QPI) technique [5]. The Fourier transform of the differential conductance scans as function of bias voltage give a fingerpr...

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Spin-singlet superconductivity with a full gap in locally noncentrosymmetric SrPtAs

Cited by 33 publications

References 26 publications

High-resolution magnetic penetration depth and inhomogeneities in locally noncentrosymmetric SrPtAs

High-resolution magnetic penetration depth and inhomogeneities in locally noncentrosymmetric SrPtAs

Multigap superconductivity in locally noncentrosymmetric SrPtAs: AnAs75nuclear quadrupole resonance investigation

Gap function of hexagonal pnictide superconductor SrPtAs from quasiparticle interference spectrum

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