Strain Engineering of Intrinsic Anomalous Hall and Nernst Effects in Altermagnetic MnTe at Realistic Doping Levels

TL;DR

This paper demonstrates that applying biaxial strain to MnTe can significantly enhance its intrinsic anomalous Hall and Nernst effects at realistic doping levels, without inducing net magnetization, by lifting symmetry-enforced Berry curvature cancellations.

Contribution

It introduces a strain engineering strategy to amplify anomalous transport effects in altermagnetic MnTe, addressing the suppression caused by symmetry in the undistorted material.

Findings

Strain lifts Berry curvature cancellation, boosting Hall conductivity.

Enhanced Nernst effect observed under strain.

Anomalous effects occur without net magnetization preservation.

Abstract

Hexagonal MnTe has emerged as a prototypical g-wave altermagnet, hosting time-reversal symmetry breaking in momentum space despite a vanishing net magnetization. While this symmetry breaking theoretically allows for an intrinsic anomalous Hall effect, experimentally observed signals have remained weak. In this work, we investigate the origin of this suppression and demonstrate a strategy to amplify anomalous transport responses within the experimentally accessible doping regime. Using a $\bm{k}\cdot\bm{p}$ effective model, we reveal that near the valence band maximum, which corresponds to the energy window relevant for typical hole doping ($\sim10^{19}cm^{-3}$), the intrinsic Hall effect is suppressed due to a symmetry-enforced cancellation of opposing Berry curvature contributions. We propose that breaking the crystalline symmetry via volume-conserving biaxial strain lifts this cancellation, resulting in a significant enhancement of the anomalous Hall conductivity by orders of magnitude. This strain-induced Fermi surface distortion also amplifies the anomalous Nernst effect. Furthermore, the analysis of the spin texture confirms that these strain-enabled anomalous transport signatures emerge while preserving the zero net magnetization.