Observation of small Fermi pockets protected by clean CuO ₂ sheets of a high- T _c superconductor

Abstract

In cuprate superconductors with high critical transition temperature (Tc), light hole-doping to the parent compound, which is an antiferromagnetic Mott insulator, has been predicted to lead to the formation of small Fermi pockets. These pockets, however, have not been observed. Here, we investigate the electronic structure of the five-layered Ba2Ca4Cu5O10(F,O)2, which has inner copper oxide (CuO2) planes with extremely low disorder, and find small Fermi pockets centered at (π/2, π/2) of the Brillouin zone by angle-resolved photoemission spectroscopy and quantum oscillation measurements. The d-wave superconducting gap opens along the pocket, revealing the coexistence between superconductivity and antiferromagnetic ordering in the same CuO2 sheet. These data further indicate that superconductivity can occur without contribution from the antinodal region around (π, 0), which is shared by other competing excitations.

Transport signatures of the pseudogap critical point in the cuprate superconductor Bi2Sr2−xLaxCuO6Lizaire1, Legros2, Gourgout3 et al. 2021Phys. Rev. B233160View full textAdd to dashboardCite

“…1) or in any other cuprate, these experimental signatures nonetheless point to some similarity between the pseudogap phase and the antiferromagnetic phase, perhaps in terms of short-range antiferromagnetic correlations. A recent ADMR study of Nd-LSCO shows that the Fermi surface is transformed upon entering the pseudogap phase [56], in a way that is consistent with small nodal hole pockets akin to those expected theoretically for a Fermi surface reconstruction controlled by the Q = (π, π ) antiferromagnetic wave vector [55,57] and recently detected experimentally (via ARPES and quantum oscillations) in the antiferromagnetic phase of a fivelayer cuprate at low doping [58].…”

Normal state specific heat in the cuprate superconductors La2−xSrxCuO4 and Bi2

“…Finally, it is interesting to compare our data on LSCO at p = 0.04 with recent quantum oscillation measurements in the five-layer cuprate Ba 2 Ca 4 Cu 5 O 10 (F, O) 2 [30]. The frequency of the oscillations coming from the innermost layer (labeled IP0) in which there is long-range antiferromagnetic order is F = 147 T. ARPES measurements show that the Fermi surface in this metal with antiferromagnetic order consists of four small closed hole pockets at nodal locations in the Brillouin zone, centered approximately at (±π/2, ±π/2) [30]. The 2D carrier density n contained by each hole pocket is given by n = F/ 0 , where 0 = h/2e.…”

Anomaly of longitudinal spin susceptibility at superconducting instability inside a magnetic phase

“…Recently direct evidence of the coexistence of superconductivity and magnetism was reported for multilayer cuprates 8,9 . Hence it is interesting to test a jump of the longitudinal spin susceptibility with a wavevector Q = (π, π) by spin-spin relaxation time in NMR or polarized neutron scattering measurements more directly.…”

“…In multilayer cuprate superconductors, early NMR measurements reported a microscopic coexistence of superconductivity and magnetism inside a CuO 2 plane 8 . Very recently angleresolved photoemission spectroscopy (ARPES) reported clear evidence of the microscopic coexistence by observing the superconducting gap along the Fermi-surface pocket reconstructed by antiferromagnetic order 9 .…”