Two energy scales and close relationship between the pseudogap and superconductivity in underdoped cuprate superconductors

Abstract

By measuring the low temperature specific heat, the low energy quasi-particle excitation has been derived and analyzed in systematically doped La${}_{2-x}$Sr${}_x$CuO${}_4$ single crystals. The Volovik's relation predicted for a d-wave superconductor has been well demonstrated in wide doping regime, showing a robust evidence for the d-wave pairing symmetry. Furthermore the nodal gap slope $v_{\Delta }$ of the superconducting gap is derived and is found to follow the same doping dependence of the pseudogap obtained from ARPES and tunnelling measurement. This strongly suggests a close relationship between the pseudogap and superconductivity. Taking the entropy conservation into account, we argue that the ground state of the pseudogap phase should have Fermi arcs with finite density of states at zero K, and the transport data show that it behaves like an insulator due to probably weak localization. A nodal metal picture for the pseudogap phase cannot interpret the data. Based on the Fermi arc picture for the pseudogap phase it is found that the superconducting energy scale or $T_c$ in underdoped regime is governed by both the maximum gap and the spectral weight from the Fermi arcs. This suggests that there are two energy scales: superconducting energy scale and the pseudogap. The superconductivity may be formed by the condensation of Fermi arc quasiparticles through pairing by exchanging virtue bosons.

4 pages, 5 figures

References in corpus (8)

• The pseudogap in high-temperature superconductors: an experimental survey
• Nodal metallic behavior of lightly-doped La${}_{2-x}$Sr${}_x$CuO${}_4$
• Fermionic entropy of the vortex state in d-wave superconductors
• Delocalized fermions in underdoped cuprates
• Electronic Specific Heat of La_{2-x}Sr_{x}CuO_{4}: Pseudogap Formation and Reduction of the Superconducting Condensation Energy
• Electronic specific heat and low energy quasiparticle excitations in superconducting state of $L{a}_{2-x}S{r}_{x}Cu{O}_4$ single crystals
• Magnetic-Field-Induced Localization of Quasiparticles in Underdoped La${}_{2-x}$Sr${}_x$CuO${}_4$ Single Crystals
• Pseudogap, Superconducting Energy Scale, and Fermi Arcs in Underdoped Cuprate Superconductors

Cited by in corpus (6)

• Specific-Heat Measurement of Residual Superconductivity in the Normal State of Underdoped Cuprate Superconductors
• A competing order scenario of two-gap behavior in hole doped cuprates
• Doping dependence of the upper critical field in La_{2-x}Sr_xCuO_4 from specific heat
• The pseudogap ground state in high temperature superconductors
• Large isotope effect on $T_c$ in cuprates despite of a small electron-phonon coupling
• Self-energy renormalization around the flux phase in the $t-J$ model: Possible implications in underdoped cuprates