Coexistence of isotropic and extended<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>s</mml:mi></mml:math>-wave order parameters in FeSe as revealed by low-temperature specific heat

Lin, Jiunn‐Yuan; Hsieh, Yih Shou; Чареев, Д. А.; Vasiliev, A. N.; Parsons, Y.; Yang, H. D.

doi:10.1103/physrevb.84.220507

Cited by 118 publications

(140 citation statements)

References 40 publications

(37 reference statements)

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“…A previous specific-heat measurement on a single crystal of FeSe 0.963 in magnetic fields up to 9 T reported a Sommerfeld coefficient of 5.73±0.13 mJ/molK 2 . 27 A recent measurement on vapor-grown FeSe at B = 14 T has found a similar value (∼5.9 mJ/molK 2 ). 28 On the other hand, the sum of the above estimated coefficients for the observed cylinders is already 6.2 mJ/molK 2 .…”

Section: -26supporting

confidence: 49%

Anomalous Fermi surface in FeSe seen by Shubnikov–de Haas oscillation measurements

et al. 2014

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We have observed Shubnikov-de Haas oscillations in FeSe. The Fermi surface deviates significantly from predictions of band-structure calculations and most likely consists of one electron and one hole thin cylinder. The carrier density is in the order of 0.01 carriers/ Fe, an order-of-magnitude smaller than predicted. Effective Fermi energies as small as 3.6 meV are estimated. These findings call for elaborate theoretical investigations incorporating both electronic correlations and orbital ordering.

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Section: -26supporting

confidence: 49%

Anomalous Fermi surface in FeSe seen by Shubnikov–de Haas oscillation measurements

et al. 2014

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“…It should be pointed out that such a small gap is also in line with specific-heat data on a similar FeSe crystal. 13 The contribution to the in-plane penetration depth data from each band is also shown in Fig. 4 by dashed and dotted lines, respectively.…”

Section: Theoretical Fitting Of the Lower Critical Fieldmentioning

confidence: 99%

“…12 The presence of both an isotropic s-wave and extended s-wave order parameters coexisting in a superconducting single-crystal FeSe has also been proposed based on specific-heat measurements. 13 Very recently, multiple Andreev reflection spectroscopy pointed to the existence of two-gap superconductivity. 7 In addition, muon-spin rotation studies of the penetration depth λ −2 ab (T ) in FeSe 0.85 were consistent with either two-gap (s + s) or anisotropic s-wave order parameter symmetries, thus implying that the superconducting energy gap contains no nodes.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of lower critical fieldHc1(T)shows nodeless superconductivity in FeSe

Abdel-Hafiez

Vasiliev

et al. 2013

Phys. Rev. B

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We investigate the temperature dependence of the lower critical field H c1 (T ) of a high-quality FeSe single crystal under static magnetic fields H parallel to the c axis. The temperature dependence of the first vortex penetration field has been experimentally obtained by two independent methods and the corresponding H c1 (T ) was deduced by taking into account demagnetization factors. A pronounced change in the H c1 (T) curvature is observed, which is attributed to anisotopic s-wave or multiband superconductivity. The London penetration depth λ ab (T ) calculated from the lower critical field does not follow an exponential behavior at low temperatures, as it would be expected for a fully gapped clean s-wave superconductor. Using either a two-band model with s-wave-like gaps of magnitudes 1 = 0.41 ± 0.1 meV and 2 = 3.33 ± 0.25 meV or a single anisotropic s-wave order parameter, the temperature dependence of the lower critical field H c1 (T ) can be well described. These observations clearly show that the superconducting energy gap in FeSe is nodeless.

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“…Also the large pressure effect on transition temperature was later observed [2][3][4] with T c ≈ 37 K at pressures P ≈ 9 GPa, indicating that FeSe 1−x is actually a high temperature superconductor. Therefore, the superconducting FeSe 1−x compound has attracted considerable attention and is a subject of intensive studies for the last years [5][6][7][8][9][10][11][12] . The structural simplicity of FeSe favors experimental and theoretical studies of chemical substitution and high pressure effects, which are aimed at promoting a better understanding of a mechanism of the superconductivity.…”

Section: Introductionmentioning

confidence: 99%

Magnetic properties of novel FeSe(Te) superconductors

Grechnev

Панфилов

Fedorchenko

et al. 2012

Journal of Magnetism and Magnetic Materials

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A detailed magnetization study for the novel FeSe superconductor is carried out to investigate the behavior of the intrinsic magnetic susceptibility χ in the normal state with temperature and under hydrostatic pressure. The temperature dependencies of χ and its anisotropy ∆χ = χ − χ ⊥ are measured for FeSe single crystals in the temperature range 4.2 − 300 K, and a substantial growth of susceptibility with temperature is revealed. The observed anisotropy ∆χ is very large and comparable with the averaged susceptibility at low temperatures. For a polycrystalline sample of FeSe, a significant pressure effect on χ is determined to be essentially dependent on temperature. Ab initio calculations of the pressure dependent electronic structure and magnetic susceptibility indicate that FeSe is close to magnetic instability with dominating enhanced spin paramagnetism. The calculated paramagnetic susceptibility exhibits a strong dependence on the unit cell volume and especially on the height Z of chalcogen species from the Fe plane. The change of Z under pressure determines a large positive pressure effect on χ which is observed at low temperatures. It is shown that the literature experimental data on the strong and nonmonotonic pressure dependence of the superconducting transition temperature in FeSe correlate qualitatively with calculated behavior of the density of electronic states at the Fermi level.

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Coexistence of isotropic and extendeds-wave order parameters in FeSe as revealed by low-temperature specific heat

Cited by 118 publications

References 40 publications

Anomalous Fermi surface in FeSe seen by Shubnikov–de Haas oscillation measurements

Anomalous Fermi surface in FeSe seen by Shubnikov–de Haas oscillation measurements

Temperature dependence of lower critical fieldHc1(T)shows nodeless superconductivity in FeSe

Magnetic properties of novel FeSe(Te) superconductors

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