The Zintl phase compounds AEIn₂As₂ (AE = Ca, Sr, Ba): topological phase transition under pressure

Abstract

AEIn2As2 (AE=Ca, Sr, Ba), as a new crucial nonmagnetic thermoelectric candidate, is desired to be understood in terms of its potential physical properties and controversial structural phases in both experimental...

Exploiting the fraternal twin nature of thermoelectrics and topological insulators in Zintl phases as a tool for engineering new efficient thermoelectric generators

“…87 Similarly, the CaIn 2 As 2 and SrIn 2 As 2 phases have been reported as TIs. 46,197 Although the experimental transport properties are yet to be reported, results from electronic structure calculation show that this phase holds some promise with enhanced TE properties. A key drawback here, however, would be the presence of As element in the phase which could pose serious health challenges.…”

“…The BaIn 2 As 2 phase has the monoclinic EuGa 2 P 2 structure type, 195 while the AEIn 2 As 2 (AE = Ca, Sr, Eu) phases have a layered centrosymmetric hexagonal structure (space group P6 3 /mmc); the latter belongs to a class of materials that have recently been studied for their topological properties. 46,196,197 The hexagonal EuIn 2 As 2 196 phase undergoes an A-type antiferromagnetic (AFM) ordering at T N = 17 K, and shows a colossal magnetoresistance (CMR) of magnitude À143% at 17.5 K and in an applied field of 5 T. Similar observations are reported in EuIn 2 P 2 198 with T N = 24 K and CMR of À298% at 24 K and in an applied field of 5 T. The EuIn 2 As 2 phase is a magnetic topological insulator with an estimated band gap, E g = 0.1 eV along the G-M direction, and where the Eu 2+ electronic state of 4f 7 is localized. Depending on the orientation of the magnetic moments, the A-type AFM order in EuIn 2 As 2 can lead to either an axion insulator (magnetic TI in which the nontrivial Z 2 index is protected by inversion symmetry instead of time-reversal symmetry) 199 or a higher-order topological insulator with chiral states existing on the hinges between the gapped surfaces.…”