P8 Spin liquids and Mott insulators with strong spin-orbit coupling

The goal of the project is to explore models for Mott insulators with strong spin-orbit coupling, to search for novel states of matter realized in these systems, and to investigate their physical properties. First, we will investigate versions of the so-called Heisenberg-Kitaev model proposed for A2IrO3. This displays a quantum phase transition between a spin-liquid and a striped antiferromagnetic phase and possibly a multicritical point in an applied field, and we intend to derive a field theory describing this physics. Second, we will re-visit the problem of magnetic impurities in the Kitaev spin liquid and discuss its relation to other impurity problems in gapless spin hosts. Third, we want to employ low-energy field theory combined with a quantum Boltzmann equation to study thermal transport in Heisenberg-Kitaev models. This requires an understanding of the scattering off both impurities and thermal excitations. Fourth, we want to extend our focus to the carrier-doped situation away from half-filling. Starting from the case of small doping, both in the spin-liquid and the magnetically ordered phases, we hope to be able to make controlled statements regarding the influence of carriers on the undoped Mott-insulating state. Finally, investigations of impurity effects and thermal transport will be performed for other spin-liquid phases as well, where, among other things, the dynamics of gauge fields becomes important.

Ph.D. students in charge: Fabian Zschocke, Darshan Joshi

additional support: Eric Andrade, Dr. Stephan Rachel

Publications

2016:

L. Janssen, E. C. Andrade, M. Vojta, Honeycomb-lattice Heisenberg-Kitaev model in a magnetic field: Spin canting, metamagnetism, and vortex crystals, Phys. Rev. Lett. 117, 277202 (2016), open access version: arXiv:1607.04640 

K. Coester, D.G. Joshi, M. Vojta, K.P. Schmidt Linked-cluster expansions for quantum magnets on the hypercubic lattice, Phys. Rev. B 94, 125109 (2016), open access version: arXiv:1605.05848

M. Laubach, D. G. Joshi, J. Reuther, R. Thomale, M. Vojta, S. Rachel, Quantum disordered insulating phase in the frustrated cubic-lattice Hubbard model, Phys. Rev. B 93, 041106(R) (2016), open access version: arXiv:1506.07894

M. Vojta, A. K. Mitchell, F. Zschocke, Kondo impurities in the Kitaev spin liquid: Numerical renormalization group solution and gauge-flux-driven screening, Phys. Rev. Lett. 117, 037202 (2016), open access version: arXiv:1604.03557

S. Rachel, L. Fritz, M. Vojta, Landau levels of Majorana fermions in a spin liquid, Phys. Rev. Lett. 116, 167201 (2016), open access version: arXiv:1509.01246

2015:

P. Baruselli, M. Vojta, Distinct topological crystalline phases in models for the strongly correlated topological insulator SmB6, Phys. Rev. Lett. 115, 156404 (2015) (arXiv:1505.03507)

I. Rousochatzakis, J. Reuther, R. Thomale, S. Rachel, N. B. Perkins, Phase Diagram and Quantum Order by Disorder in the Kitaev K1-K2 Honeycomb Magnet, Phys. Rev. X 5, 041035 (2015) (open access)

F. Zschocke and M. Vojta, Physical states and finite-size effects in Kitaev's honeycomb model: Bond disorder, spin excitations, and NMR lineshape, Phys. Rev. B 92, 014403 (2015), open access version: arXiv:1502.03063

D. G. Joshi, K. Coester, K. P. Schmidt, and M. Vojta, Non-linear bond-operator theory and 1/d expansion for coupled-dimer magnets, I. Paramagnetic phase, Physical Review B 91, 094404 (2015), open access version: arXiv:1407.7870

D. G. Joshi and M. Vojta, Non-linear bond-operator theory and 1/d expansion for coupled-dimer magnets II: Antiferromagnetic phase and quantum phase transition, Phys. Rev. B 91, 094405 (2015), open access version: arXiv:1411.7033

2014:

E. C. Andrade, M. Vojta, Magnetism in spin models for depleted honeycomb-lattice iridates: Spin-glass order towards percolation, Phys. Rev. B 90, 205112 (2014), open access version: arxiv.:1309.2951

P. P. Baruselli, M. Vojta, Scanning tunneling spectroscopy and surface quasiparticle interference in models for the strongly correlated topological insulators SmB6 and PuB6, Phys. Rev. B 90, 201106(R) (2014), open access version: arxiv:1409.6722

M. Laubach, J. Reuther, R. Thomale, S. Rachel,  Rashba spin orbit coupling in the Kane-Mele-Hubbard model, Phys. Rev. B 90, 165136 (2014), open access version: arxiv:1312.2934

J. Reuther, R. Thomale, S. Rachel, Spiral order in the honeycomb iridate Li2IrO3, Phys. Rev. B 90, 100405(R) (2014), open access version: arXiv:1404.5818

P. P. Baruselli, M. Vojta, Kondo holes in topological Kondo insulators: Spectral properties and surface quasiparticle interference, Phys Rev B 89, 205105 (2014), open access version: arXiv:1403.3566

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