Pseudogap Behavior in the Electronic Specific Heat of La_2−xSr_xCuO₄

Abstract

In La214, the electronic specific heat coefficient γ (=C _el /T) is gradually suppressed with lowering T below a certain temperature T* (> T _c ), where the in-plane resistivity ρ and magnetic susceptibility χ also tend to be suppressed slightly. Temperature T*, increasing with lowering x, is in qualitative agreement with the mean field T _c (T _co ), estimated from the superconducting gap amplitude 2Δ _o at T ≪ T _c , as the onset temperature T* of a pseudogap in Bi2212. The gradual suppression of γ below ∼ T _co implies that a pseudogap will also open up below ∼ T _co in La214 as in Bi2212. In underdoped samples, whose pseudogap-like behaviors in C _el(T) become marked, the anomaly of C _el around T _c is rather different from the BCS expectation.