Dirac fermion transport coupled with magnetic order in a layered antiferromagnet EuMnBi2

Datum

25.07.2017

Zeit

14:00 - 15:00

Sprecher

Prof. Hideaki Sakai

Zugehörigkeit

Osaka University, Japan

Sprache

en

Hauptthema

Physik

Andere Themen

Physik

Host

Prof. Dr. A. Mackenzie, Dr. C. Hicks

Beschreibung

Dirac fermions in solids have been of current interest for spintronic applications as well as basic science, because a variety of quantum transport phenomena manifest themselves in an external magnetic field. In addition to the half-integer quantum Hall effect (QHE) in graphene, more recently, the quantum anomalous Hall effect was observed for the surface Dirac state in magnetic topological insulator thin films [1]. To further unveil such a distinct quantum transport enriched by magnetic order, it is desirable to explore bulk systems that host various magnetism and dimensionality. In this work, as an ideal arena for magnetically-controllable Dirac fermions, we have focused on a layered bulk antiferromagnet EuMnBi2 [2,3], where the Bi1- layer hosting quasi 2D Dirac fermions and the magnetic blocking layer (Eu2+ and Mn2+-Bi3- layers) stack alternatively (inset to Fig. 1). From detailed transport measurements at high magnetic fields, we found that the antiferromagnetic order of the Eu sublattice has a marked impact on the transport properties. As shown in Fig. 1(a), the orientation of the ordered Eu moments can be controlled by applying magnetic fields along the c axis, which strongly modifies the interlayer coupling between the conducting Bi layers. When the Eu moments flop in the ab plane (H>Hf), zz increases by about one order of magnitude, followed by giant SdH oscillations [Fig. 1(b)]. This indicates that the 2D confinement of Dirac fermions is largely enhanced by flopping the Eu moments. In this high-zz state, interestingly, we observed plateau-like structures in the Hall resistivity concomitantly with deep minima in the in-plane resistivity, which signifies the half-integer QHE even in a bulk magnet [3]. I am also talking about some recent progresses on this material. [1] C-Z, Chang et al., Science 340, 167 (2013). [2] A. F. May et. al., Phys. Rev. B 90, 075109 (2014). [3] H. Masuda et al., Sci. Adv. 2, e1501117 (2016).

Links

• MPI CPfS

Letztmalig verändert: 25.07.2017, 09:45:49