Electronic structure of the honeycomb iridate Cu2⁢IrO3 at high pressure

Fabbris, G.; Poldi, E. T.; Sinha, S.; Lim, J.; Elmslie, T.; Kim, J. H.; Said, A.; Upton, M.; Abramchuk, M.; Bahrami, F.; Kenney-Benson, C.; Park, C.; Shen, G.; Vohra, Y. K.; Hemley, R. J.; Hamlin, J. J.; Tafti, F.; Haskel, D.

doi:10.1103/physrevb.111.075153

Electronic structure of the honeycomb iridate Cu₂⁢IrO₃ at high pressure

Journal Article · Thu Feb 20 00:00:00 EST 2025 · Physical Review. B

DOI:https://doi.org/10.1103/physrevb.111.075153· OSTI ID:2551888

^[1]; ^[2]; ^[3]; ^[4]; ^[3]; ^[1]; Said, A. ^[1]; Upton, M. ^[1]; Abramchuk, M. ^[5]; Bahrami, F. ^[5]; ^[1]; ^[1]; ^[1]; ^[6]; ^[7]; Hamlin, J. J. ^[3]; ^[5]; ^[1]

Argonne National Laboratory (ANL), Argonne, IL (United States)
Argonne National Laboratory (ANL), Argonne, IL (United States); University of Illinois at Chicago, IL (United States)
University of Florida, Gainesville, FL (United States)
University of Florida, Gainesville, FL (United States); Eastern Illinois University, Charleston, IL (United States)
Boston College, Chestnut Hill, MA (United States)
University of Alabama at Birmingham, AL (United States)
University of Illinois at Chicago, IL (United States)

Cu₂IrO₃ has attracted recent interest due to its proximity to the Kitaev quantum spin liquid state and the complex structural response observed at high pressures. We use x-ray spectroscopy and scattering as well as electrical transport techniques to unveil the electronic structure of Cu₂IrO₃ at ambient and high pressures. Despite featuring a Ir⁴⁺ J_eff = 1/2 state at ambient pressure, Ir L₃-edge resonant inelastic x-ray scattering reveals broadened electronic excitations that point to the importance of Ir 5d-Cu 3d interaction. High pressure first drives an Ir-Ir dimer state with collapsed < L · S > and < L_z >/< S_z >, signaling the formation of 5d molecular orbitals. A novel Cu → Ir charge transfer is observed above 30 GPa at low temperatures, leading to an approximate Ir³⁺ and Cu^1.5+ valence, with persistent insulating electrical transport seemingly driven by charge segregation of Cu¹⁺/Cu²⁺ ions into distinct sites. Concomitant x-ray spectroscopy and diffraction measurements through different thermodynamic paths demonstrate a strong electron-lattice coupling, with J_eff = 1/2 and Ir³⁺/Cu^1.5+ electronic states occurring only in phases 1 and 5, respectively. Remarkably, the charge-transfer state can only be reached if Cu₂IrO₃ is pressurized at low temperature, suggesting that phonons play an important role in the inhibiting this phase. Furthermore, these results point to the choice of thermodynamic path across interplanar collapse transition as a key parameter to access novel states in intercalated iridates.

View Accepted Manuscript (DOE)

Research Organization:: University of Illinois, Chicago, IL (United States)

Sponsoring Organization:: National Science Foundation (NSF); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)

Grant/Contract Number:: AC02-06CH11357; NA0003975; NA0004153; SC0023124

OSTI ID:: 2551888

Journal Information:: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 7 Vol. 111; ISSN 2469-9950

Publisher:: American Physical Society (APS)Copyright Statement

Country of Publication:: United States

Language:: English

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