"Magnetic monopole" condensation of the pyrochlore ice U(1) quantum spin liquid: Application to Pr2Ir2 O7 and Yb2Ti2 O7

Abstract

©2016 American Physical Society. Pyrochlore iridates and pyrochlore ices are two families of materials where novel quantum phenomena are intertwined with strong spin-orbit coupling, substantial electron correlation, and geometrical frustration. Motivated by the puzzling experiments on two pyrochlore systems Pr2Ir2O7 and Yb2Ti2O7, we study the proximate Ising orders and the quantum phase transition out of quantum spin ice U(1) quantum spin liquid (QSL). We apply the electromagnetic duality of the compact quantum electrodynamics to analyze the condensation of the "magnetic monopoles" in the U(1) QSL. The monopole condensation naturally and necessarily leads to the Ising orders that generically break the lattice translation symmetry. We demonstrate that the antiferromagnetic Ising order with the ordering wave vector Q=2π(001) is proximate to the U(1) QSL while the ferromagnetic Ising state with Q=(000) is not proximate to the U(1) QSL. This implies that if there exists a direct transition from the U(1) QSL to the ferromagnetic Ising order, the transition must be strongly first order. We apply the monopole condensation to explain the magnetic orders and the transitions in Pr2Ir2O7 and Yb2Ti2O7.