Quantum phase transition in La_1−xBa_xTiO_3+δ∕2: Evidence from resistivity measurements

Abstract

The temperature and doping dependence of resistivity ( ρ ) and thermopower ( S ) of La_1−xBa_xTiO_3+δ∕2 have been studied systematically. We observe a quantum phase transition at around x_c = 0.25 . Below this critical value of doping, ρ shows T²dependence due to the electron-electron correlation which is a characteristic feature of Fermi liquid. However, above x_c , ρ exhibits T^{3 ∕ 2} behavior. This unusual T^{3 ∕ 2} dependence of ρ may be understood on the basis of scattering of the conduction electrons by locally cooperative bond-length fluctuations as observed in other strongly correlated systems. The thermopower is negative and shows almost linear temperature dependence for x < 0.70 .