Impact of disorder on dynamics and ordering in the honeycomb lattice iridate Na$_2$IrO$_3$
Autor: | Alejandro Ruiz, James Analytis, Hans-Henning Klauss, Ziwen Mei, Gilbert Lopez, Itamar Kimchi, N. J. Curro, Rajib Sarkar |
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Rok vydání: | 2019 |
Předmět: |
Physics
Condensed matter physics Strongly Correlated Electrons (cond-mat.str-el) Magnetism FOS: Physical sciences 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Spectral line Magnetic field Paramagnetism Condensed Matter - Strongly Correlated Electrons Relaxation rate Lattice (order) 0103 physical sciences Condensed Matter::Strongly Correlated Electrons Quantum spin liquid 010306 general physics 0210 nano-technology Quantum |
DOI: | 10.48550/arxiv.1909.09356 |
Popis: | Kitaev's honeycomb spin-liquid model and its proposed realization in materials such as $\alpha$-RuCl$_3$, Li$_2$IrO$_3$ and Na$_2$IrO$_3$ 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 $^{23}$Na nuclear magnetic resonance to probe both static and dynamical magnetic properties in single crystal Na$_2$IrO$_3$. We find that the NMR shift follows the bulk susceptibility above 30 K but deviates from it below; moreover below $T_N$ 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 $T_N$, suggesting that the Kitaev cubic axes may control the critical quantum spin fluctuations. 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. Comment: To appear in PRB as Rapid Communication |
Databáze: | OpenAIRE |
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