Anomalies of the electronic heat capacity of thulium cuprates in the pseudogap phase region

Abstract

Precise calorimetric measurements have been carried out in the 7 -300 K temperature range on two ceramic samples of thulium 123 cuprates TmBa 2 Cu 3 O 6.92 and TmBa 2 Cu 3 O 6.70 . The temperature dependence of the heat capacity was analyzed in the region where the pseudogap state (PGS) takes place. The lattice contribution was subtracted from the experimental data. The PGS component has been obtained by comparing electronic heat capacities of two investigated samples because the PGS contribution for the 6.92 sample is negligible. The anomalous behavior of the electronic heat capacity near the temperature boundary of PGS was found. It is supposed that this anomaly is due to peculiarities in N(E) function where N is the density of electronic states and E is the energy of carriers of charge.

Pseudogap effects in strongly correlated electron systems

“…As to the question of the order of the transition on crossing the phase boundaries, one can disagree with the reasoning of the authors. First, the very existence of a phase transition in connection with the appearance of a pseudogap state is confirmed in a single paper, 14 which reported measurements of the heat capacity of underdoped cuprates. If a phase transition occurs, then the presence of an observed separation region attesting to the coexistence of the CDW and UCDW phases compels the assumption that here we are dealing with a first-order transition.…”