Low-energy quasiparticles in high- T c cuprates

Hussey, N. E.

doi:10.1080/00018730210164638

Cited by 151 publications

(160 citation statements)

References 212 publications

(357 reference statements)

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“…It can be seen clearly that γ(H) increases almost linearly with the magnetic field in the temperature region up to 11 K. A linear fit with the slope of about 0.633 mJ/molK 2 T to the zero temperature data is revealed by the blue solid line in this figure. This linear behavior is actually anticipated by the theoretical prediction for superconductors with a full gap [29], in which γ(H) is mainly contributed by the localized quasiparticle DOS within vortex cores. This is in sharp contrast with the results in cuprates [30,31] and the LaFeAsO 0.9 F 0.1−δ system [4] where a γ(H) ∝ √ H relation was observed and attributed to the Doppler shift of the nodal quasiparticle spectrum.…”

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confidence: 48%

Low temperature specific heat of the hole-dopedBa0.6K0.4Fe2As2
Mu
¹
,
Luo
²
,
Wang
³

et al. 2009
Phys. Rev. B
180
31
179
3
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We report the specific heat (SH) measurements on single crystals of hole doped FeAs-based superconductor Ba 0.6 K 0.4 Fe 2 As 2 . It is found that the electronic SH coefficient γ e (T ) is not temperature dependent and increases almost linearly with the magnetic field in low temperature region. These point to a fully gapped superconducting state. Surprisingly the sharp SH anomaly ∆C/T | Tc reaches a value of 98 mJ/molK 2 suggesting a very high normal state quasiparticle density of states (γ n ≈ 63mJ/molK 2 ). A detailed analysis reveals that the γ e (T ) cannot be fitted with a single gap of s-wave symmetry due to the presence of a hump in the middle temperature region. However, our data indicate that the dominant part of the superconducting condensate is induced by an s-wave gap with the magnitude of about 6 meV. PACS numbers: 74.20.Rp, 74.25.Bt, 65.40.Ba, 74.70.Dd The discovery of high temperature superconductivity in the FeAs-based system has stimulated enormous interests in the field of condensed matter physics and material sciences [1]. The superconductivity has not only been discovered in the electron doped samples, but also in the hole-doped ones [2,3]. The central issues concerning the superconductivity mechanism are about the symmetry and the magnitude of the superconducting gap. The experimental results obtained so far are, however, highly controversial. The low temperature specific heat (SH) measurements in the F-doped LaFeAsO samples revealed a nonlinear magnetic field dependence of the SH coefficient γ e , which was attributed to the presence of a nodal gap [4]. This was later supported by many other measurements based on µSR [5,6,7], NMR[8, 9, 10], magnetic penetration [11] and point contact Andreev spectrum (PCAS) [12]. On the other hand, the PCAS on the Fdoped SmFeAsO indicated a feature of s-wave gap [13], some measurements [14,15,16,17] also gave support to this conclusion. It is important to note that most of the conclusions drawn for a nodal gap were obtained on the electron doped LnFeAsO samples (abbreviated as FeAs-1111, Ln stands for the rare earth elements) which are characterized by a low charge carrier density and thus low superfluid density [18]. For the FeAs-1111 phase, it is very difficult to grow crystals with large sizes, therefore most of the measurements on the pairing symmetry so far were made on polycrystalline samples. This is much improved in the (Ba, S r) 1−x K x Fe 2 As 2 (denoted as FeAs-122) system since sizable crystals can be achieved [19,20]. Preliminary data by angle resolved photoemission spectroscopy (ARPES) on these crystals show two groups of superconducting gaps (∆ 1 ≈ 12 meV, ∆ 2 ≈ 6 meV) all with s-wave symmetry [21,22,23]. It is known that the surface of this type of single crystals decay or reconstruct very quickly, this may give obstacles to get repeatable data when using the surface sensitive tools. Thus solid conclusions about the gap symmetry and magnitude from bulk measurements are highly desired.Specific heat (SH) is one of the powerful tools to meas...

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confidence: 48%

Low temperature specific heat of the hole-dopedBa0.6K0.4Fe2As2
Mu
¹
,
Luo
²
,
Wang
³

et al. 2009
Phys. Rev. B
180
31
179
3
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“…Inside the vortex cores, the superfluid current is significantly reduced by the magnetic field. The low-energy fermionic excitations in the mixed state are expected to have rather different lowenergy behaviors comparing with those in the uniform zero-field condensate 3 . As revealed by heat transport measurements, the thermal conductivity loses its universality and depends on the impurity scattering rate 3 .…”

Section: Introductionmentioning

confidence: 99%

Paring instability in the mixed state of ad-wave superconductor

2009

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We propose that an excitonic gap can be generated along nodal directions by Coulomb interaction in the mixed state of d-wave cuprate superconductors. In a superconductor, the Coulomb interaction usually can not generate any fermion gap since its strength is weakened by superfluidity. It becomes stronger as superfluid density is suppressed by external magnetic field, and is able to generate a gap for initially gapless nodal quasiparticles beyond some critical field Hc. By solving the gap equation, it is found that the nodal gap increases with growing field H, which leads to a suppression of thermal conductivity at zero temperature. This mechanism naturally produces the field-induced thermal metal-insulator transition observed in transport experiments.

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“…For example, for the s-wave superconductor Nb, a deviation from a linear field fit is clearly seen above a crossover magnetic field H * ∼ 0.25H C2 18 . For p-doped cuprate superconductors, the √ H dependence has been reported for many crystals in support of d-wave pairing symmetry 19,23 . However, there are also a few exceptions that need to be clarified 19 .…”

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confidence: 99%

“…For p-doped cuprate superconductors, the √ H dependence has been reported for many crystals in support of d-wave pairing symmetry 19,23 . However, there are also a few exceptions that need to be clarified 19 .…”

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confidence: 99%

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Magnetic-field dependence of the low-temperature specific heat of the electron-doped superconductorPr1.85Ce0.15CuO4

Liang

Greene

2005

Phys. Rev. B

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Magnetic field dependence of the low-temperature specific heat of the electron-doped superconductor Pr We remeasured the magnetic field dependence of the low-temperature specific heat of the electrondoped superconductor Pr1.85Ce0.15CuO4 (TC = 22 ± 2K) under a different measurement procedure. Under field-cooling, the electronic specific heat follows C el (H, T ) = γ(H)T from 4.5K down to 1.8K. In the field range HC1 < H < 0.5HC2, the Sommerfeld coefficient γ(H) is well fit by a power-law γ(H) ∼ H 1/2 . This result suggests that the pairing symmetry is d-wave-like at all temperatures below 4.5K. Our new measurement shows no evidence for the linear field dependence of γ(H) found previously at T = 2K.

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Low-energy quasiparticles in high- T c cuprates

Cited by 151 publications

References 212 publications

Low temperature specific heat of the hole-dopedBa0.6K0.4Fe2As2
Mu
¹
,
Luo
²
,
Wang
³

et al. 2009
Phys. Rev. B
180
31
179
3
View full text Add to dashboard Cite

Low temperature specific heat of the hole-dopedBa0.6K0.4Fe2As2
Mu
¹
,
Luo
²
,
Wang
³

et al. 2009
Phys. Rev. B
180
31
179
3
View full text Add to dashboard Cite

Paring instability in the mixed state of ad-wave superconductor

Magnetic-field dependence of the low-temperature specific heat of the electron-doped superconductorPr1.85Ce0.15CuO4

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Low-energy quasiparticles in high- T c cuprates

Cited by 151 publications

References 212 publications

Low temperature specific heat of the hole-dopedBa0.6K0.4Fe2As2Mu1, Luo2, Wang3 et al. 2009Phys. Rev. B180311793View full textAdd to dashboardCite

Low temperature specific heat of the hole-dopedBa0.6K0.4Fe2As2Mu1, Luo2, Wang3 et al. 2009Phys. Rev. B180311793View full textAdd to dashboardCite

Paring instability in the mixed state of ad-wave superconductor

Magnetic-field dependence of the low-temperature specific heat of the electron-doped superconductorPr1.85Ce0.15CuO4

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Low temperature specific heat of the hole-dopedBa0.6K0.4Fe2As2
Mu
¹
,
Luo
²
,
Wang
³

et al. 2009
Phys. Rev. B
180
31
179
3
View full text Add to dashboard Cite

Low temperature specific heat of the hole-dopedBa0.6K0.4Fe2As2
Mu
¹
,
Luo
²
,
Wang
³

et al. 2009
Phys. Rev. B
180
31
179
3
View full text Add to dashboard Cite