In-plane antiferromagnetic moments in axion topological insulator candidate EuIn$_2$As$_2$

Abstract

Topological insulator with antiferromagnetic order can serve as an ideal platform for the realization of axion electrodynamics. In this paper, we report a systematic study of the axion topological insulator candidate EuIn2As2. A linear energy dispersion across the Fermi level confirms the existence of the proposed hole-type Fermi pocket. Spin-flop transitions occur with magnetic fields applied within the ab-plane while are absent for fields parallel to the c-axis. Anisotropic magnetic phase diagrams are observed and the orientation of the ground magnetic moment is found to be within the ab-plane. The magnetoresistivity for EuIn2As2 behaves non-monotonic as a function of field strength. It exhibits angular dependent evolving due to field-driven and temperature-driven magnetic states. These results indicate that the magnetic states of EuIn2As2 strongly affect the transport properties as well as the topological nature.

Signature of band inversion in the antiferromagnetic phase of axion insulator candidate EuIn2As2

“…Amongst various magnetic topological materials, axion insulator is currently attracting a particular attention since it is predicted to host topological magnetoelectric effect associated with a hypothetic quasiparticle called axion. While axion insulator was proposed to be realized in various systems such as heterostruc-tures involving quantum anomalous Hall insulators 11,12 and magnetically doped TIs 8,13 , the experimental investigation of axion insulators with stoichiometric intrinsic magnetic TIs is still limited to a few materials class [14][15][16][17][18][19][20][21][22] . Axion-insulator phase with inherent antiferromagnetic (AFM) order was recently proposed in MnBi 2 Te 4 family 14,[16][17][18][19][20][23][24][25][26] ; however its axioninsulator nature, e.g.…”

“…Moreover, the AFM c state also hosts an axion-insulator phase, but it coexists with higher-order TI state with chiral hinge mode 27 . Despite such intriguing theoretical predictions, the electronic state of EuIn 2 As 2 has been scarcely investigated by experiments 21,22 . It is thus highly desired to clarify the band structure of EuIn 2 As 2 .…”