Heat transport as a probe of superconducting gap structure

Shakeripour, H.; Petrović, C.; Taillefer, Louis

doi:10.1088/1367-2630/11/5/055065

Cited by 100 publications

(184 citation statements)

References 34 publications

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“…However, for unconventional superconductors with nodes in the superconducting gap, the nodal quasiparticles will [16]. Therefore, the significant 0 =T of our BaðFe 0:64 Ru 0:36 Þ 2 As 2 in zero field is strong evidence for nodes in the superconducting gap [32].…”

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confidence: 75%

Robust Nodal Superconductivity Induced by Isovalent Doping inBa(Fe1−xRux)2As2and
Qiu
¹
,
Zhou
²
,
Zhang
³

et al. 2012
Phys. Rev. X
43
1
17
0
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We present the ultra-low-temperature heat-transport study of iron-based superconductors BaðFe 1Àx Ru x Þ 2 As 2 and BaFe 2 ðAs 1Àx P x Þ 2 . For optimally doped BaðFe 0:64 Ru 0:36 Þ 2 As 2 , a large residual 0 =T at zero field and a ffiffiffiffi ffi H p dependence of 0 ðHÞ=T are observed, which provide strong evidences for nodes in the superconducting gap. This result demonstrates one more nodal superconductor in iron pnictides. The similarities between isovalent Fe and P dopings strongly suggest that the nodal superconductivity in Since the discovery of high-T c superconductivity in iron pnictides [1,2], the issue of what mechanisms underlie the electron pairing in these systems has been a central one [3]. One key step in resolving it is to clarify the symmetry and structure of the superconducting gap [4]. However, even for the most studied ðBa; Sr; Ca; EuÞFe 2 As 2 (122) system, the situation is still fairly complex [4].Near optimal doping where the T c is the highest, for both hole-and electron-doped 122 compounds, the angleresolved photon-emission-spectroscopy (ARPES) experiments have clearly demonstrated multiple nodeless superconducting gaps [5,6]. Those experiments have been further supported by measurements of bulk properties such as thermal conductivity [7][8][9]. On the overdoped (with respect to the optimal doping) side, nodal superconductivity has been found in the extremely hole-doped KFe 2 As 2 [10,11], while a strongly anisotropic nodeless gap [9] or isotropic nodeless gaps with significantly different magnitudes [12,13] have been suggested in heavily electron-doped BaðFe 1Àx Co x Þ 2 As 2 . On the underdoped side, recent heat-transport measurements have claimed possible nodes in the superconducting gap of hole-doped Ba 1Àx K x Fe 2 As 2 with x < 0:16 [14], in contrast to the nodeless gaps that have been found in electron-doped BaðFe 1Àx Co x Þ 2 As 2 [9]. It is hard to get a simple pairing mechanism from such complex situation of the superconducting gap structure.More intriguingly, nodal superconductivity has also been found in optimally doped BaFe 2 ðAs 0:67 P 0:33 Þ 2 (T c ¼ 30K) [15,16], in which the superconductivity is induced by isovalent P doping. Moreover, LaFePO (T c $6K) was found to display clear nodal behavior [17][18][19], and recently evidence for nodes in the superconducting gap of LiFeP (T c $ 4:5 K) has emerged from measurements of magnetic penetration depth [20]. The nodal superconductivity in these P-doped compounds is very striking, which raises the puzzling questions of whether, and why, the P doping is unique among iron-based superconductors. Although various theoretical explanations have been offered for this puzzle, investigators are far from reaching consensus [21][22][23][24][25].A recent empirical proposal is that the nodal state in ironpnictide superconductors, except for KFe 2 As 2 , is induced when the pnictogen height h Pn from the iron plane decreases below a threshold value of approximately 1:33 A [20]. According to this proposal, there may exist a transition from...

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confidence: 75%

Robust Nodal Superconductivity Induced by Isovalent Doping inBa(Fe1−xRux)2As2and
Qiu
¹
,
Zhou
²
,
Zhang
³

et al. 2012
Phys. Rev. X
43
1
17
0
View full text Add to dashboard Cite

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“…At H = 0, κ/T drops below T c , and decreases monotonically to reach a non-zero residual value at T = 0 [30,31], the signature of nodes in the superconducting gap [34]. The drop is simply due to a loss of thermally excited quasiparticles [35].…”

Section: Pacs Numbersmentioning

confidence: 98%

Quantum Critical Quasiparticle Scattering within the Superconducting State ofCeCoIn5

et al. 2016

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The thermal conductivity κ of the heavy-fermion metal CeCoIn5 was measured in the normal and superconducting states as a function of temperature T and magnetic field H, for a current and field parallel to the [100] direction. Inside the superconducting state, when the field is lower than the upper critical field Hc2, κ/T is found to increase as T → 0, just as in a metal and in contrast to the behavior of all known superconductors. This is due to unpaired electrons on part of the Fermi surface, which dominate the transport above a certain field. The evolution of κ/T with field reveals that the electron-electron scattering (or transport mass m ) of those unpaired electrons diverges as H → Hc2 from below, in the same way that it does in the normal state as H → Hc2 from above. This shows that the unpaired electrons sense the proximity of the field-tuned quantum critical point of CeCoIn5 at H = Hc2 even from inside the superconducting state. The fact that the quantum critical scattering of the unpaired electrons is much weaker than the average scattering of all electrons in the normal state reveals a k-space correlation between the strength of pairing and the strength of scattering, pointing to a common mechanism, presumably antiferromagnetic fluctuations. PACS numbers:With the discovery of iron-based superconductors [1], the interplay of magnetism and superconductivity has become an increasingly important topic of condensed matter physics. The archetypal evidence of magneticallymediated superconductivity in the heavy-fermion metal CeIn 3 [2] linked unconventional Cooper pairing with magnetic fluctuations emanating from a quantum critical point (QCP), a scenario widely believed to explain the common appearance of superconductivity in the vicinity of antiferromagnetic order in heavy fermion, organic, pnictide and cuprate families of superconductors [3].The heavy-fermion superconductor CeCoIn 5 [8] continues to receive considerable attention [4][5][6][7]. Lowtemperature transport [9,32] and specific heat [10] studies have revealed a magnetic field-tuned QCP, with a critical field H that anomalously coincides with H c2 , the upper critical field for superconductivity. The pinning of H to H c2 was subsequently shown to hold regardless of field orientation [11] or suppression of the superconducting state by impurities [12], suggesting a novel form of quantum criticality closely linked with the superconducting state. Recent work has revealed other examples of systems that appear to have a field-tuned QCP pinned to H c2 , including cuprates [13,14] and iron pnictides [15].Together with large angle scattering evidence [32], the presence of similar critical behavior in the ordered antiferromagnet CeRhIn 5 under pressure [16] strongly suggests that the QCP for H c configuration in CeCoIn 5 is also magnetic in nature, although magnetic order was not observed in muon spin rotation [17] or neutron scattering measurements [18]. However, for H ab neutron scattering [19,20] and nuclear magnetic resonance [21] measurements have found...

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“…The first term, a ≡ κ 0 /T , is the residual linear term, entirely due to electronic excitations. 42 The second term is due to phonons, which at low temperature are scattered by the sample boundaries, with 1 < α < 2.…”

Section: B Thermal Conductivitymentioning

confidence: 99%

Doping evolution of the superconducting gap structure in the underdoped iron arsenideBa1−xKxFe2As2revealed by thermal conducti

et al. 2016

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Heat transport as a probe of superconducting gap structure

Cited by 100 publications

References 34 publications

Robust Nodal Superconductivity Induced by Isovalent Doping inBa(Fe1−xRux)2As2and
Qiu
¹
,
Zhou
²
,
Zhang
³

et al. 2012
Phys. Rev. X
43
1
17
0
View full text Add to dashboard Cite

Robust Nodal Superconductivity Induced by Isovalent Doping inBa(Fe1−xRux)2As2and
Qiu
¹
,
Zhou
²
,
Zhang
³

et al. 2012
Phys. Rev. X
43
1
17
0
View full text Add to dashboard Cite

Quantum Critical Quasiparticle Scattering within the Superconducting State ofCeCoIn5

Doping evolution of the superconducting gap structure in the underdoped iron arsenideBa1−xKxFe2As2revealed by thermal conducti

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Heat transport as a probe of superconducting gap structure

Cited by 100 publications

References 34 publications

Robust Nodal Superconductivity Induced by Isovalent Doping inBa(Fe1−xRux)2As2andQiu1, Zhou2, Zhang3 et al. 2012Phys. Rev. X431170View full textAdd to dashboardCite

Robust Nodal Superconductivity Induced by Isovalent Doping inBa(Fe1−xRux)2As2andQiu1, Zhou2, Zhang3 et al. 2012Phys. Rev. X431170View full textAdd to dashboardCite

Quantum Critical Quasiparticle Scattering within the Superconducting State ofCeCoIn5

Doping evolution of the superconducting gap structure in the underdoped iron arsenideBa1−xKxFe2As2revealed by thermal conducti

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Robust Nodal Superconductivity Induced by Isovalent Doping inBa(Fe1−xRux)2As2and
Qiu
¹
,
Zhou
²
,
Zhang
³

et al. 2012
Phys. Rev. X
43
1
17
0
View full text Add to dashboard Cite

Robust Nodal Superconductivity Induced by Isovalent Doping inBa(Fe1−xRux)2As2and
Qiu
¹
,
Zhou
²
,
Zhang
³

et al. 2012
Phys. Rev. X
43
1
17
0
View full text Add to dashboard Cite