Abstract
Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions.
Highlights
The kagome lattice structure, which consists of corner-sharing triangles, is notorious for supporting exotic states of matter
The spin-orbit coupling opens a gap at the position of the Dirac point and the non-trivial topology of electrons on the kagome lattice leads to surface states of both spin species that traverse the bulk band gap opened by relativistic effects and, the quantum spin Hall effect (QSHE) is realized
Evaluating density functional theory (DFT) total energies, we show that single crystals of materials obtained by following various doping choices in herbertsmithite can in principle be synthesized
Summary
The kagome lattice structure, which consists of corner-sharing triangles, is notorious for supporting exotic states of matter. The spin-orbit coupling opens a gap at the position of the Dirac point and the non-trivial topology of electrons on the kagome lattice leads to surface states of both spin species that traverse the bulk band gap opened by relativistic effects and, the QSHE is realized. It was recently suggested[36] that if a nearly flat band is partially filled, a proper combination of spin-orbit coupling, ferromagnetism and geometric frustration will give rise to the fractional quantum Hall effect at high temperatures Along these lines, we exploit here as a key ingredient for topological non-trivial states, the tendency towards ferromagnetism[37] of a filled flat band in hole-doped transition-metal-based kagome lattices. To demonstrate this new strategy of finding QSHE and QAHE materials by doping Mott insulators, we investigate which possible modifications of the natural mineral herbertsmithite -a Mott insulator with spin-liquid behavior- leave the perfect kagome motif undistorted and realize different electronic fillings
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