Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators

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.

Tuning of a Kagome Magnet: Insulating Ground State in Ga‐Substituted Cu4(OH)6Cl2

“…Since the c‐axis is influenced most, it is plausible to assume that the Ga ion mainly goes into the Cu‐position between the kagome planes. Furthermore, also theoretical calculations suggest no Ga on the intraplane Cu‐positions . A real refinement of the data with the Ga occupation on Cu sites as a free parameter cannot be performed, due to the similar scattering cross‐section of these two atoms, a similar problem to that which occurred for Zn and Cu in herbertsmithite.…”

“…Furthermore, also theoretical calculations suggest no Ga on the intraplane Cu-positions. [11] A real refinement of the data with Table 1. Average substitution factor x from EDX measurements on the Ga x Cu 4-x (OD) 6 Cl 2 powder series for the different batches as explained in section 3.1.…”

“…[6,9] Recently, a high potential is seen in chemical doping a kagome system since Mazin et al [10] have proposed that a correlated Dirac metal can be found in electron-doped herbertsmithite which might be realized by replacing Zn by a trivalent ion. [10,11] There, GaCu 3 (OH) 6 Cl 2 was suggested as the ideal candidate for an electron doped kagome system, since even when including correlation effects to the calculation, the proposed bandstructure shows the exotic phenomena of a Dirac metal. Experimentally, it turned out to be challenging to synthesize samples of doped herbertsmithite.…”

Local study of the insulating quantum kagome antiferromagnets YCu3(OH)6OxCl3−xBarthélemy1, Puphal2, Zoch3 et al. 2019Phys. Rev. Materials348574View full textAdd to dashboardCite

“…The QSL ground states that originate in both cases from the low dimensionality and the set of frustrated interactions appears as a good playground for doping in order to reach superconductivity. Besides, adding carriers in a kagome Mott insulator is interesting in itself, considering the inherent hexagonal symmetry: for a n = 4/3 filling, the band structure is predicted to feature Dirac cones at the Fermi level [12,13].…”

Nature of optical excitations in the frustrated kagome compound herbertsmithite

“…They are key ingredients of high-T c cuprates and have been widely investigated in the last decades. A recent revival of interest in Cu-based materials was triggered by the discovery of geometrically frustrated cuprates that seem to exhibit spin-liquid properties [7][8][9][10][11][12][13][14][15][16] and may even harbor unconventional superconductivity with higher angular momenta than existing superconductors [17] or further topological phases [18] although synthesis seems to be difficult [19].In this work we investigate the origin of the optical excitations in the spin-liquid candidate Herbertsmithite and concentrate on the following conceptual issue: which measurable properties in correlated systems are strongly affected by correlation effects and which are not? We will show, experimentally and theoretically, that in a single experimental probe, namely optical conductivity, one can simultaneously observe properties dramatically influenced by Coulomb (Mott-Hubbard) correlation effects, and those that are hardly affected at all.…”