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TT: Fachverband Tiefe Temperaturen

TT 71: Correlated Electrons: Poster Session

TT 71.26: Poster

Mittwoch, 18. März 2015, 15:00–18:00, Poster B

Magnetic field and impurity studies in Kitaev and Kitaev Heisenberg models — •Sitikantha Das¹, Zhu Zengwei², Ross McDonald², Suchitra Sebastian¹, and Vikram Tripathi³ — ¹Cavendish Labs, Cambridge — ²National High Magnetic Field Laboratory, Los Alamos — ³Tata Institute of Fundamental Research, Mumbai

In an effort to find an experimental realisation of Kitaev physics in solid state systems, the layered alkali iridates A₂IrO₃ (A = Li, Na), seem to be promising material candidates. Although the spin-1/2 Kitaev model has a quantum spin-liquid ground state with short ranged spin correlations and low-energy emergent excitations that are dispersing Majorana fermions, it has now been established that Na₂IrO₃ orders into a zig-zag state below 15 K. We have performed pulsed magnetic field torque experiments on Na₂IrO₃ at various field orientations and we observe strong angular dependence. Using negative Kitaev-Heisenberg as a model, we attempt to study the magnetisation and torque using exact diagonalization with a view to understand the experimental data.

We also study the effect of coupling an external magnetic impurity to a Kitaev model numerically. Antiferromagnetic coupling of the impurity spin results in the creation of finite flux excitations, which is now known from analytical calculations. This is verified numerically and we also study the effect of tuning the coupling strength from antiferromagnetic to ferromagnetic interaction.