Ground state in proximity to a possible Kitaev spin liquid: The undistorted honeycomb iridate NaxIrO3 (0.60 ≤ x ≤ 0.80)

Zhao, Hengdi; Hu, Bing; Ye, Feng; Lee, Minhyea; Schlottmann, Pedro; Cao, Gang

doi:10.1103/physrevb.104.l041108

Ground state in proximity to a possible Kitaev spin liquid: The undistorted honeycomb iridate Na_xIrO₃ (0.60 ≤ x ≤ 0.80)

Journal Article · Tue Jul 20 00:00:00 EDT 2021 · Physical Review B

DOI:https://doi.org/10.1103/physrevb.104.l041108· OSTI ID:1817382

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Univ. of Colorado, Boulder, CO (United States)
Univ. of Colorado, Boulder, CO (United States); North China Electric Power Univ., Beijing (China)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Florida State Univ., Tallahassee, FL (United States)

Here, we report the results of our study of a recently synthesized honeycomb iridate Na_xIrO₃ (0.60 ≤ x ≤ 0.80). Single-crystal Na_xIrO₃ adopts a honeycomb lattice noticeably without distortions and stacking disorder inherently existent in its sister compound Na₂IrO₃. The oxidation state of the Ir ion is a mixed valence state resulting from a majority Ir⁵⁺(5d⁴) ion and a minority Ir⁶⁺(5d³) ion. Na_xIrO₃ is a Mott insulator likely with a predominant pseudospin =1 state. It exhibits an effective moment of 1.1 μB/Ir and a Curie-Weiss temperature of –19 K but with no discernible long-range order above 1 K. The physical behavior below 1 K features two prominent anomalies at T_h = 0.9 K and T_l = 0.12 K in both the heat capacity and AC magnetic susceptibility. Intermediate between T_h and T_l lies a pronounced temperature linearity of the heat capacity with a large slope of 77 mJ /mole K², a feature expected for highly correlated metals but not at all for insulators. These results along with a comparison drawn with the honeycomb lattices Na₂IrO₃ and (Na_0.2Li_0.8)₂IrO₃ point to an exotic ground state in proximity to a possible Kitaev spin liquid.

View Accepted Manuscript (DOE)

Research Organization:: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC05-00OR22725

OSTI ID:: 1817382

Journal Information:: Physical Review B, Journal Name: Physical Review B Journal Issue: 4 Vol. 104; ISSN 2469-9950

Publisher:: American Physical Society (APS)Copyright Statement

Country of Publication:: United States

Language:: English

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Ground state in proximity to a possible Kitaev spin liquid: The undistorted honeycomb iridate Na_xIrO₃ (0.60 ≤ x ≤ 0.80)