Metamagnetism, Criticality and Dynamics in the Quantum Spin Ice Pr2Zr2O7

Geometrical frustration may prevent the formation of long-range magnetic order, giving rise to a diverse range of novel ground states. One of such an unusual state is called quantum spin liquid (QSL) possibly realized in quantum spin ice systems. Its excitations behave like charged particles interacting with linearly dispersive “photon”, protected by hidden topological order parameter. Yet, the properties of quantum phase transition between such topological phases remain unknown and are waiting to be established.
Pr-based pyrochlore compounds such as Pr₂Ir₂O₇ and Pr₂Zr₂O₇ are known to be quantum spin ice systems. Pr₂Ir₂O₇ is a fascinating material exhibiting various exotic phenomena such as the spontaneous anomalous Hall effect [1]. In contrast to Pr₂Ir₂O₇, the insulating Pr₂Zr₂O₇ renders a simplified platform to explore the physics of quantum spin ice. K. Kimura et al. [2] reported the absence of “pinch points” in the inelastic neutron scattering spectrum of Pr₂Zr₂O₇, suggesting the breakdown of the ice rule owing to quantum fluctuations — a promising hint of a U(1) QSL state. In a recent study [3], it was found that structural disorder acts as a transverse field on the non-Kramers Pr³⁺ ion in Pr₂Zr₂O₇, stabilizing the QSL state. Under a magnetic field along the [111] axis, classical spin ice materials undergo a 1st-order metamagnetic transition [4]. Although theoretical studies [5] predict the existence of metamagnetic transition in quantum spin ice, a comprehensive investigation is still lacking. Here, we report magnetization, thermal expansion, and magnetostriction measurements on Pr₂Zr₂O₇. These measurements aim to clarify the nature of the metamagnetic transition and to probe possible topological quantum criticality.
Reference
[1] Y. Machida et al., Nature 463, 210 (2010) [2] K. Kimura et al., Nat. Commun. 4, 1934 (2013) [3] J.-J. Wen, PRL 118, 107206 (2017) [4] T.Sakakibara et al., PRL 90, 207205 (2003) [5] T.A. Bojesen, and S.Onoda, PRL 119, 227204 (2017)