Quantum anomalous Hall (QAH) phase is a two-dimensional bulk ferromagnetic insulator with a nonzero Chern number in presence of spin-orbit coupling (SOC) but in the absence of applied magnetic fields. Associated metallic chiral edge states host dissipationless current transport in electronic devices. This intriguing QAH phase has recently been observed in magnetic impurity-doped topological insulators, albeit, at extremely low temperatures. Based on first-principles density functional calculations, here we predict that layered rhodium oxide K0.5RhO2 in noncoplanar chiral antiferromagnetic state is an unconventional three-dimensional QAH insulator with a large band gap and a Neel temperature of a few tens Kelvins. Furthermore, this unconventional QAH phase is revealed to be the exotic quantum topological Hall effect caused by nonzero scalar spin chirality due to the topological spin structure in the system and without the need of net magnetization and SOC.

 

fig2

 

This paper is published on Physical Review Letters 116, 256601 (2016).

Link to the full text: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.256601

June 24, 2016

We report an atomic-scale characterization of ZrTe5 by using scanning tunneling microscopy. We observe a bulk band gap of ∼80 meV with topological edge states at the step edge and, thus, demonstrate that ZrTe5 is a two-dimensional topological insulator. We also find that an applied magnetic field induces an energetic splitting of the topological edge states, which can be attributed to a strong link between the topological edge states and bulk topology. The relatively large band gap makes ZrTe5 a potential candidate for future fundamental studies and device applications.

 

ZrTe5 paper

 

This paper is published on Physical Review Letters 116, 176803 (2016).

Link to the full text: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.176803

May 21, 2016