Pressure tuning of structure, magnetic frustration, and carrier conduction in the Kitaev spin liquid candidate Cu2IrO3

Abstract

The layered honeycomb lattice iridate Cu 2 IrO 3 is the closest realization of the Kitaev quantum spin liquid, primarily due to the enhanced interlayer separation and nearly ideal honeycomb lattice. We report pressureinduced structural evolution of Cu 2 IrO 3 by powder x-ray diffraction (PXRD) up to ∼17 GPa and Raman scattering measurements up to ∼25 GPa. A structural phase transition (monoclinic C2/c → triclinic P 1) is observed with a broad mixed phase pressure range (∼4 to 15 GPa). The triclinic phase consists of heavily distorted honeycomb lattice with Ir-Ir dimer formation and a collapsed interlayer separation. In the stability range of the low-pressure monoclinic phase, structural evolution maintains the Kitaev configuration up to 4 GPa. This is supported by the observed enhanced magnetic frustration in dc susceptibility without emergence of any magnetic ordering and an enhanced dynamic Raman susceptibility. High-pressure resistance measurements up to 25 GPa in the temperature range 1.4-300 K show resilient nonmetallic R(T ) behavior with significantly reduced resistivity in the high-pressure phase. The Mott 3D variable-range-hopping conduction with much reduced characteristic energy scale T 0 suggests that the high-pressure phase is at the boundary of localized-itinerant crossover. First-principles density functional theoretical (DFT) analysis shows that monoclinic P2 1 /c phase of Cu 2 IrO 3 is energetically lower than its C2/c phase at ambient pressure and both the structures are consistent with experimental XRD pattern. Our analysis reveals structural transition from P2 1 /c to P 1 structure at 7 GPa in agreement with experiment and uncovers the interplay between oxidation states, spin, Ir bond dimerization and their relevance to electronic band gap.

Role of V–V dimerization on electronic and magnetic properties of ilmenite-type CoVO3

“…Herein, we have came up with judgment that the introduction of other magnetic ions in ilmenite-type cobaltates may bring in unexpected and complex structural variation and/or magnetic interactions, blurring the delicate balance to accomplish the sought after quantum spin liquid. In this regard, the effort to approach to the ideal Kitaev model by reducing structural distortion through application of pressure [23]in ilmenite-type compounds or exploring other systems not containing second magnetic ions [3,4], may represent an exciting future research direction, by which can afford a deeper understanding.…”

Structural phase transformation of quantum spin liquid herbertsmithite via pressure induced enhancement of the cooperative Jahn–Teller effect and antisite disorder

“…Hence the QSL materials have captured increasing attention in the field of high pressure research. [23][24][25] Among them herbertsmithite can be an ideal model system for the high pressure studies of kagome QSL materials on account of the structure-property correlation under compression. It has been observed that herbertsmithite undergoes a transition from the quantum-disordered spin liquid phase to the longrange ordered antiferromagnetic phase at 2.5 GPa and the R% 3m symmetry is preserved up to at least 5 GPa.…”