Topological end states in two-orbital double-exchange model for colossal magnetoresistive manganites

TL;DR

This paper investigates the topological properties of antiferromagnetic phases in manganites, revealing that E-type phases are weak topological insulators and CE-type phases belong to a new topological class, with implications for colossal magnetoresistance.

Contribution

It introduces a topological classification of zigzag antiferromagnetic phases in manganites, identifying new topological insulator classes and analyzing their edge states.

Findings

E-type phase is a weak topological insulator with $ ext{Z}$ classification.

CE-type phase described by Duffin-Kemmer-Petiau algebra, indicating a new topological class.

Numerical calculations show topological end states consistent with experimental ferromagnetic edge states.

Abstract

Manganites are famous mostly for the colossal magnetoresistive effect, which involves the phase separation between ferromagnetic phase and charge-ordered CE-type antiferromagnetic phases. Furthermore, manganites contain some typical magnetic ferroelectrics, e.g. E-type antiferromagnetic $o$-HoMnO$_3$. Here we re-examined these zigzag-winding antiferromagnetic phases (CE-type and E-type antiferromagnets) from the topological perspective. Our theoretical analysis proved that the E-type phase is a weak topological insulator belonging to the $\mathbb{Z}$ class. In momentum space, we classify the symmetries of this phase, and find the three symmetry operators for the chiral, particle-hole, and time-reversal symmetry. The CE-type phase can be described by the Duffin-Kemmer-Petiau algebra, implying that it is a new class of topological insulator and hence extends the existing classification. The corresponding topological end states are demonstrated via numerical calculations, which may implicate the experimental observed ferromagnetic edge states in manganite strips (Nat. Commun. 6, 6179 (2015)) and may play a crucial role in the colossal magnetoresistive effect.