The uniform spin susceptibility, χs, is determined from the Gd3+ high frequency ESR Knight shift in the underdoped high temperature superconductor, Gd:YBa2Cu4O8 \(Tc = 82 K\) between 8 to 260 K. Measurements at two fields (5.4 and 8.1 T) permit high precision at low temperatures. In the range of 0.1Tc to 0.4Tc, a linear temperature dependence of χs is observed with a large slope. The corresponding maximum d-wave superconducting gap is Δ0 = 190 K, 1.1 times the weakly coupled d-wave limit. The results support suggestions that the normal state gap observed below 180 K and the superconducting gap below Tc have nodes with the same symmetry.
ASJC Scopus subject areas
- Physics and Astronomy(all)