High-pressure insulator-to-metal transition in Sr${}_3$Ir${}_2$O${}_7$ studied by x-ray absorption spectroscopy

Abstract

High-pressure x-ray absorption spectroscopy was performed at the Ir $L_3$ and $L_2$ absorption edges of Sr${}_3$Ir${}_2$O${}_7$. The branching ratio of white line intensities continuously decreases with pressure, reflecting a reduction in the angular part of the expectation value of the spin-orbit coupling operator, $⟨\mathbf{L}\cdot \mathbf{S}⟩$. Up to the high-pressure structural transition at 53 GPa, this behavior can be explained within a single-ion model, where pressure increases the strength of the cubic crystal field, which suppresses the spin-orbit induced hybridization of $J_{\text{eff}}=3/2$ and $e_g$ levels. We observe a further reduction of the branching ratio above the structural transition, which cannot be explained within a single-ion model of spin-orbit coupling and cubic crystal fields. This change in $⟨\mathbf{L}\cdot \mathbf{S}⟩$ in the high-pressure, metallic phase of Sr${}_3$Ir${}_2$O${}_7$ could arise from non-cubic crystal fields or a bandwidth-driven hybridization of $J_{\text{eff}}=1/2,3/2$ states, and suggests that the electronic ground state significantly deviates from the $J_{\text{eff}}=1/2$ limit.

8 pages, 5 figures

References in corpus (8)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
• Bandwidth-Controlled Insulator-Metal Transition and Correlated Metallic State in 5$d$ Transition Metal Oxides Sr${}_{n+1}$Ir${}_n$O${}_{3n+1}$ ($n$=1, 2, and $\infty$)
• Twisted Hubbard Model for Sr2IrO4: Magnetism and Possible High Temperature Superconductivity
• Crystal field splitting and correlation effect on the electronic structure of A2IrO3
• Testing the validity of the strong spin-orbit-coupling limit for octahedrally coordinated iridates in a model system Sr${}_3$CuIrO${}_6$
• The J_{eff}=1/2 insulator Sr3Ir2O7 studied by means of angle-resolved photoemission spectroscopy
• Crystal field splitting in Sr${}_{n+1}$Ir${}_n$O${}_{3n+1}$ ($n$ = 1, 2) iridates probed by x-ray Raman spectroscopy

Cited by in corpus (1)

• Revisiting the Kitaev material candidacy of Ir4+ double perovskite iridates