Thermal conductivity across the phase diagram of cuprates: Low-energy quasiparticles and doping dependence of the superconducting gap

Sutherland, M.; Hawthorn, D. G.; Hill, R. W.; Ronning, F.; Wakimoto, Shuichi; Zhang, H.; Proust, Cyril; Boaknin, Etienne; Lupien, Christian; Taillefer, Louis; Liang, Ruixing; Bonn, D. A.; Hardy, W. N.; Gagnon, R.; Hussey, N. E.; Kimura, Takashi; Nohara, M.; Takagi, H.

doi:10.1103/physrevb.67.174520

Cited by 237 publications

(260 citation statements)

References 49 publications

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“…Specifically, both the EDC leading edge method and the symmetrized EDC methods have a short 'arc' near the node, in which the extracted gap value is either zero or negative (which is often artificially set to zero). Directly observing the sharp cusp of the d-wave gap so near the node confirms the findings of other probes such as thermal conductivity 27 . By comparing Fig.…”

supporting

confidence: 71%

The origin and non-quasiparticle nature of Fermi arcs in Bi2Sr2CaCu2O8+δ

et al. 2012

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A Fermi arc 1,2 is a disconnected segment of a Fermi surface observed in the pseudogap phase 3,4 of cuprate superconductors. This simple description belies the fundamental inconsistency in the physics of Fermi arcs, specifically that such segments violate the topological integrity of the band 5 . Efforts to resolve this contradiction of experiment and theory have focused on connecting the ends of the Fermi arc back on itself to form a pocket, with limited and controversial success 6-9 . Here we show the Fermi arc, although composed of real spectral weight, lacks the quasiparticles to be a true Fermi surface 5 . To reach this conclusion we developed a new photoemission-based technique that directly probes the interplay of pair-forming and pair-breaking processes with unprecedented precision. We find the spectral weight composing the Fermi arc is shifted from the gap edge to the Fermi energy by pair-breaking processes 10 . Although real, this weight does not form a true Fermi surface, because the quasiparticles, although significantly broadened, remain at the gap edge. This non-quasiparticle weight may account for much of the unexplained behaviour of the pseudogap phase of the cuprates.

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confidence: 71%

The origin and non-quasiparticle nature of Fermi arcs in Bi2Sr2CaCu2O8+δ

et al. 2012

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“…The data below 0.35 K are fitted to κ/T = a + bT α−1 , in which the two terms aT and bT α represent contributions from fermionic zero-energy excitations and phonons, respectively [37,38]. Because of the specular reflections of phonons at the sample surfaces, the power α in the second term is typically between 2 and 3 [37,38]. The fitting gives κ 0 /T = -0.003 ± 0.004 mW K −2 cm −1 and α = 2.94.…”

mentioning

confidence: 99%

Bulk Fermi Surface of Charge-Neutral Excitations inSmB6or Not: A Heat-Transport Study

Cui

Dong

et al. 2016

Phys. Rev. Lett.

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Recently there have been increasingly hot debates on whether a bulk Fermi surface of chargeneutral excitations exists in the topological Kondo insulator SmB6. To unambiguously resolve this issue, we performed the low-temperature thermal conductivity measurements of a high-quality SmB6 single crystal down to 0.1 K and up to 14.5 T. Our experiments show that the residual linear term of thermal conductivity at zero field is zero, within the experimental accuracy. Furthermore, the thermal conductivity is insensitive to magnetic field up to 14.5 T. These results exclude the existence of fermionic charge-neutral excitations in bulk SmB6, such as scalar Majorana fermions or spinons, thus put a strong constraint on the explanation of the quantum oscillations observed in SmB6.Topological insulator is a novel quantum state of matter, and has been suggested theoretically and observed experimentally [1][2][3][4][5]. Like the edge channel found in the quantum Hall system, the strong spin-orbit coupling in a three dimensional topological insulator leads to a nontrivial and robust conducting surface state. This metallic state is protected by the time-reversal symmetry. Studies on topological insulators have later stimulated the search for many other topological materials, such as topological crystalline insulators, Weyl and Dirac semimetals, and topological Kondo insulator [6][7][8][9]. Especially, interaction effect could play an important role in topological Kondo insulators and render exotic physics in them.As one of the most historical heavy-fermion (HF) materials, SmB 6 has been studied for more than 50 years [10,11] and was recently shown to be a topological Kondo insulator [12]. For decades, the low-temperature conductivity in SmB 6 remains puzzling: its resistivity shows insulating behavior down to a few Kelvins but saturates down to the lowest temperature upon further reducing the temperature. This puzzle was successfully resolved by recent transport experiments, which show that the material is a bulk insulator but with a metallic surface [13,14], consistent with the theoretical prediction that SmB 6 is a topological Kondo insulator [9,[15][16][17]. At high temperatures, transport properties are dominated by thermal excitations in the insulating bulk, and thus insulating behaviors are observed. At low temperatures, however, bulk excitations vanishes because of the energy gap, and surface signals become dominant. The existence of the metallic surface states is now well established and observed in a number of experiments [18][19][20][21][22][23][24][25][26][27][28][29][30][31].Although electric transport measurements so far show that the bulk of SmB 6 has no gapless charge carriers (namely a finite charge-gap), there exist other experiments suggesting possible gapless excitations in the bulk. Especially, the recent quantum oscillation measurement claims multiple Fermi seas in the bulk of an insulating SmB 6 sample [20], in direct contradiction with transport measurements. As the electrical transport only measures the ch...

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“…Cooper pairs are pre-formed at a particular temperature T * > T c (pseudogap temperature) above the superconducting dome in the underdoped region [9,10] (where T c is smaller than the higher T c possible), and they undergo a Bose-Einstein Condensation (BEC) as temperature is lowered [11,12]. There are many other characteristics, but of special interest to us are some recently reported experimental results: the modification of the size of the lattice with oxygen doping [13]; the notorious increase of the superconducting gap magnitude [14] and the dramatic drop of the Fermi temperature T F when doping is diminished [15]. These features are of crucial importance in our results.…”

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confidence: 99%

“…For f = 1 we recover the case where all pairable fermions participate in the boson gas. Additional experimental parameters of YBa 2 Cu 3 O 6.80 that we use in our calculations are: the critical temperature [13] T cexp = 88 K; the superconducting parameter [14] ∆ 0 = 50 meV; the crystallographic [13] c = 11.71Å, giving a = c/2 = 5.855Å and a/λ 0 = 0.233. Finally, we take the height of the jump ∆C/T c ≃ 20 mJ/mol K 2 from the data published in Ref.…”

Section: Cmentioning

confidence: 99%

Specific heat of underdoped cuprate superconductors from a phenomenological layered Boson–Fermion model

Salas

Fortes

Solís

et al. 2016

Physica C: Superconductivity and its Applications

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We adapt the Boson-Fermion superconductivity model to include layered systems such as underdoped cuprate superconductors. These systems are represented by an infinite layered structure containing a mixture of paired and unpaired fermions. The former, which stand for the superconducting carriers, are considered as noninteracting zero spin composite-bosons with a linear energymomentum dispersion relation in the CuO2 planes where superconduction is predominant, coexisting with the unpaired fermions in a pattern of stacked slabs. The inter-slab, penetrable, infinite planes are generated by a Dirac comb potential, while paired and unpaired electrons (or holes) are free to move parallel to the planes. Composite-bosons condense at a critical temperature at which they exhibit a jump in their specific heat. These two values are assumed to be equal to the superconducting critical temperature Tc and the specific heat jump reported for YBa2Cu3O6.80 to fix our model parameters namely, the plane impenetrability and the fraction of superconducting charge carriers. We then calculate the isochoric and isobaric electronic specific heats for temperatures lower than Tc of both, the composite-bosons and the unpaired fermions, which matches recent experimental curves. From the latter, we extract the linear coefficient (γn) at Tc, as well as the quadratic (αT 2 ) term for low temperatures. We also calculate the lattice specific heat from the ARPES phonon spectrum, and add it to the electronic part, reproducing the experimental total specific heat at and below Tc within a 5% error range, from which the cubic (ßT 3 ) term for low temperatures is obtained. In addition, we show that this model reproduces the cuprates mass anisotropies.

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Thermal conductivity across the phase diagram of cuprates: Low-energy quasiparticles and doping dependence of the superconducting gap

Cited by 237 publications

References 49 publications

The origin and non-quasiparticle nature of Fermi arcs in Bi2Sr2CaCu2O8+δ

The origin and non-quasiparticle nature of Fermi arcs in Bi2Sr2CaCu2O8+δ

Bulk Fermi Surface of Charge-Neutral Excitations inSmB6or Not: A Heat-Transport Study

Specific heat of underdoped cuprate superconductors from a phenomenological layered Boson–Fermion model

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