Pressure-induced hole delocalization in the strongly correlated quasicubic charge-transfer perovskite $LaB{a}_{2}F{e}_3{O}_{8+\delta }$d

Abstract

Analysis of the thermal and baric evolution of resistance in $LaB{a}_{2}F{e}_3{O}_{8+\delta }$ enabled the construction of its pressure-temperature (P-T) phase diagram, which prominently displays a critical boundary, $P_c^{MIT}(T)$, marking the transition from localized to hole-type extended states. The relatively low critical pressures [$P_c^{MIT}(T)\approx 3$-8 GPa] suggest that, as $P\to P_c$ in this narrow-gap, strongly correlated charge-transfer system, both the hybridization strength and the charge-transfer character are progressively enhanced - ultimately leading to the emergence of metallicity. Emphasizing the electronic nature of this transition, pressure-dependent structural analyses at room temperature reveal no associated structural phase transition at $P_c^{MIT}(T)$; the system retains a (weakly tetragonally distorted) quasicubic perovskite structure with Murnaghan-type compressibility up to 30\,GPa. The emergence of hole delocalization and metallic conduction, coupled with suppressed antiferromagnetism, suggests proximity to quantum criticality.

9 pages, 5 figures