Disorder-sensitive nodelike small gap in FeSe

Sun, Yue; Kittaka, Shunichiro; Nakamura, Shota; Sakakibara, Toshiro; Zhang, P.; Shin, Shik; Irie, Koki; Nomoto, Takuya; Machida, Kazushige; Chen, Jingting; Tamegai, T.

doi:10.1103/physrevb.98.064505

Cited by 17 publications

(13 citation statements)

References 44 publications

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“…Much of the controversy about the low-energy gap structure of FeSe is then related to the observation of a linear behavior of the low-temperature specific heat [21] and/or the presence (or absence) of a hump around 1K [14,17], making it difficult to determine the "true" superconducting gap of "ideal" FeSe (several specific heat studies from the literature are compared in [21], clearly showing that there is no clear relationship between a higher T c and the existence/nonexistence of the 1 K humplike behavior). We show here that the various low-temperature behaviors can be [18]. Full lines are the model calculations, taking into account QP weights displayed in Fig.…”

Section: B Specific Heatmentioning

confidence: 86%

“…The absolute superconducting contribution to the specific heat C/T = (C S − C N )/T , measured on our samples and taken from various studies of the literature [18,21], are displayed in Fig. 3.…”

Section: B Specific Heatmentioning

confidence: 99%

“…Even if the presence of nodes as well as the s ± symmetry remain debated, many thermodynamic, transport and magnetic studies have confirmed the anisotropic multigap character of FeSe [12][13][14][15][16][17][18][19][20][21]. However, a major weakness of "standard" multigap fits to the data is the weight of each gap in the total fits.…”

Section: Introductionmentioning

confidence: 99%

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Influence of the quasiparticle spectral weight in FeSe on spectroscopic, magnetic, and thermodynamic properties

et al. 2019

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We report on an extensive experimental and numerical study of the low-energy electronic properties of superconducting FeSe single crystals, using point-contact Andreev reflection Spectroscopy (PCAR), specific heat, and London penetration depth measurements. Taking explicitly into account Fermi surface anisotropy and recently suggested orbital-selective quasiparticle spectral weights Z i (i = d xy , d x 2 −y 2 , d xz , d yz , d z 2), our calculations quantitatively account for all our measurements as well as data from the literature, assuming that Z yz > Z xz > Z xy. This study confirms the picture of a highly different quantum coherence of the Fe orbitals at the Fermi energy. In particular, the normal state properties (Sommerfeld coefficient and zero-temperature London penetration depth) strongly depend on the Z i values, which seem to be significantly sensitive to disorder.

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Section: B Specific Heatmentioning

confidence: 86%

Section: B Specific Heatmentioning

confidence: 99%

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Influence of the quasiparticle spectral weight in FeSe on spectroscopic, magnetic, and thermodynamic properties

et al. 2019

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“…[compare with a similar solution in the dice model in [34]]. The second solution with the negative sign before the square root in the equation above leads to a divergent wave function at ρ = 0 and should be rejected.…”

Section: Expansion In Seriesmentioning

confidence: 96%

Electron states for gapped pseudospin-1 fermions in the field of a charged impurity

2019

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The electron states of gapped pseudospin-1 fermions of the α − T3 lattice in the Coulomb field of a charged impurity are studied. The free α − T3 model has three dispersive bands with two energy gaps between them depending on the parameter Θ which controls the coupling of atoms of honeycomb lattice with atoms in the center of each hexagon, thus, interpolating between graphene Θ = 0 and the dice model Θ = π/4. The middle band becomes flat one with zero energy in the dice model. The bound electron states are found in the two cases: the centrally symmetric potential well and a regularized Coulomb potential of the charged impurity. As the charge of impurity increases, bound state energy levels descend from the upper and central continua and dive at certain critical charges into the central and lower continuum, respectively. In the dice model, it is found that the flat band survives in the presence of a potential well, however, is absent in the case of the Coulomb potential. The analytical results are presented for the energy levels near continuum boundaries in the potential well. For the genuine Coulomb potential, we present the recursion relations that determine the coefficients of the series expansion of wave functions of bound states. It is shown that the condition for the termination of the series expansion gives two equations relating energy and charge values. Hence, analytical solutions can exist for a countably infinite set of values of impurity charge at fixed Θ.

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“…In summary, the numerous studies agree on the point that FeSe exhibits a strongly anisotropic superconducting order parameter. Nodes, if these are detected, might be lifted easily by external manipulations or due to disorder [188] although the critical temperature does not seem to be very sensitive to such effects [179]. In addition, the appearance of a feature in the specific heat at very low temperatures [179] seems to be present in some samples only.…”

Section: Thermodynamic Probe Of Quasiparticle Excitationsmentioning

confidence: 99%

On the Remarkable Superconductivity of FeSe and Its Close Cousins

2020

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Emergent electronic phenomena in iron-based superconductors have been at the forefront of condensed matter physics for more than a decade. Much has been learned about the origins and intertwined roles of ordered phases, including nematicity, magnetism, and superconductivity, in this fascinating class of materials. In recent years, focus has been centered on the peculiar and highly unusual properties of FeSe and its close cousins. This family of materials has attracted considerable attention due to the discovery of unexpected superconducting gap structures, a wide range of superconducting critical temperatures, and evidence for nontrivial band topology, including associated spin-helical surface states and vortex-induced Majorana bound states. Here, we review superconductivity in iron chalcogenide superconductors, including bulk FeSe, doped bulk FeSe, FeTe1−xSex, intercalated FeSe materials, and monolayer FeSe and FeTe1−xSex on SrTiO3. We focus on the superconducting properties, including a survey of the relevant experimental studies, and a discussion of the different proposed theoretical pairing scenarios. In the last part of the paper, we review the growing recent evidence for nontrivial topological effects in FeSe-related materials, focusing again on interesting implications for superconductivity.

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Disorder-sensitive nodelike small gap in FeSe

Cited by 17 publications

References 44 publications

Influence of the quasiparticle spectral weight in FeSe on spectroscopic, magnetic, and thermodynamic properties

Influence of the quasiparticle spectral weight in FeSe on spectroscopic, magnetic, and thermodynamic properties

Electron states for gapped pseudospin-1 fermions in the field of a charged impurity

On the Remarkable Superconductivity of FeSe and Its Close Cousins

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