The Hall–Lorenz number in the La1.855Sr0.145CuO4 single crystal

The temperature dependence of the Hall–Lorenz number ( L xy ) for the optimally doped La1.855Sr0.145CuO4 (LSCO) has been obtained from the experimentally determined transverse and longitudinal transport coefficients. A comparison between L x y ( T ) dependence found for LSCO and L x y ( T ) reported previously for copper indicates that the Hall–Lorenz number in LSCO follows standard metallic behavior from room temperature down to T ∼ 150 K . Below this temperature the L x y coefficient deviates from regular metallic dependence in a way characteristic of an electronic system with lowered density of electronic states at the Fermi level. We present results of calculations provided in terms of the Boltzmann equation for a two-dimensional model of the electronic structure with a d-symmetrical pseudogap. A temperature T max , where a maximum in the L x y ( T ) dependence appears, turns out to be dependent on the width of the supposed pseudogap ( E g max ) . The best agreement between the model and the experimental data was obtained for E g max ∼ 25 meV , which corresponds well with values reported previously by other groups.