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Title: Impact of disorder on dynamics and ordering in the honeycomb-lattice iridate Na 2 IrO 3

Journal Article · · Physical Review B
ORCiD logo [1];  [2];  [3];  [3]; ORCiD logo [1];  [3];  [4]; ORCiD logo [2]
  1. Technical Univ. of Dresden, Dresden (Germany). Inst. of Solid State and Materials Physics
  2. Univ. of California, Davis, CA (United States). Dept. of Physics
  3. Univ. of California, Berkeley, CA (United States). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Univ. of Colorado, Boulder, CO (United States); National Inst. of Standards and Technology (NIST), Boulder, CO (United States). JILA

Kitaev's honeycomb spin-liquid model and its proposed realization in materials such as α-RuCl3, Li 2IrO3, and Na2IrO3 continue to present open questions about how the dynamics of a spin liquid are modified in the presence of non-Kitaev interactions as well as the presence of inhomogeneities. Here we use 23Na nuclear magnetic resonance to probe both static and dynamical magnetic properties in single-crystal Na2IrO3 . We find that the NMR shift follows the bulk susceptibility above 30 K but deviates from it below; moreover below TN the spectra show a broad distribution of internal magnetic fields. Both of these results provide evidence for inequivalent magnetic sites at low temperature, suggesting inhomogeneities are important for the magnetism. The spin-lattice relaxation rate is isotropic and diverges at TN, suggesting that the Kitaev cubic axes may control the critical quantum spin fluctuations. Finally, in the ordered state, we observe gapless excitations, which may arise from site substitution, emergent defects from milder disorder, or possibly be associated with nearby quantum paramagnetic states distinct from the Kitaev spin liquid.

Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); German Research Foundation (DFG); National Science Foundation (NSF)
Grant/Contract Number:
AC02-05CH11231; DMR-1506961; DMR-1807889
OSTI ID:
1616111
Journal Information:
Physical Review B, Vol. 101, Issue 8; ISSN 2469-9950
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 4 works
Citation information provided by
Web of Science

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