Effect of symmetry breaking on altermagnetism in CrSb and Formation of fragmented nodal curves

TL;DR

This study investigates how symmetry breaking in CrSb and related structures influences altermagnetism, leading to the formation of fragmented nodal curves and potential for anomalous Hall effects, with implications for quantum device applications.

Contribution

It reveals the formation of fragmented nodal curves due to reduced symmetry in altermagnetic CrSb, validated by DFT and strain analysis, expanding understanding of symmetry effects on altermagnetism.

Findings

Symmetry reduction from six-fold to two-fold induces FNCs.

FNCs are band-specific and can manifest AHC.

Strain and doping influence FNC formation and properties.

Abstract

Phenomena concerning altermagnets have opened up a window for unconventional analysis of the momentum space spin polarization (MSSP) of antiferromagnetic materials. Taking the example of one of the widely investigated altermagnets, CrSb, we explore the underlying mechanisms leading to the formation or breaking of altermagnetism. With the aid of DFT calculation and symmetry analysis, we study the behavior of MSSP in the altermagnetic bands of pristine CrSb, along with a few model structures designed from the pristine one by hypothetical vacancy engineering and interstitial doping. We show that the six-fold rotational symmetry of the pristine CrSb can be reduced to a two-fold rotational symmetry via vacancy and doping engineering. We discover the formation of fragmented nodal curves (FNCs) across the Brillouin zone when in an altermagnetic material when the symmetry is restricted to two-fold rotation. Unlike the typical nodal planes and axes, the location of the FNCs in the momentum space is found to be band-specific. The formation of FNCs is further validated by introducing uniaxial strain to CrSb and by examining the band structure of RbMnPO$_4$, as they both exhibit a two-fold rotational symmetry responsible for altermagnetism. We observe that, unlike the pristine case, these FNCs have the potential to manifest anomalous Hall conductivities (AHC), while the N\'eel vector orients along both in-plane and out-of-plane directions. This flexibility of the AHC will pave the way for the application of altermagnets in the futuristic quantum devices.