Co-existence of Topological Non-trivial and Spin Gapless Semiconducting Behavior in MnPO$_4$: A Composite Quantum Compound

TL;DR

This paper predicts a novel quantum compound, MnPO$_4$, exhibiting both topologically non-trivial Weyl semimetal and spin gapless semiconducting behaviors, combining distinct quantum phenomena in a single material using ab-initio calculations.

Contribution

It introduces the first prediction of a single crystalline system displaying co-existing Weyl semimetal and spin gapless semiconductor properties.

Findings

Weyl nodes are close to the Fermi level with minimal trivial band density.

A drumhead surface state from a nodal loop is observed.

High anomalous Hall conductivity indicates topological behavior.

Abstract

Composite quantum compounds (CQC) are classic example of quantum materials which host more than one apparently distinct quantum phenomenon in physics. Magnetism, topological superconductivity, Rashba physics etc. are few such quantum phenomenon which are ubiquitously observed in several functional materials and can co-exist in CQCs. In this letter, we use {\it ab-initio} calculations to predict the co-existence of two incompatible phenomena, namely topologically non-trivial Weyl semimetal and spin gapless semiconducting (SGS) behavior, in a single crystalline system. SGS belong to a special class of spintronics material which exhibit a unique band structure involving a semiconducting state for one spin channel and a gapless state for the other. We report such a SGS behavior in conjunction with the topologically non-trivial multi-Weyl Fermions in MnPO$_4$. Interestingly, these Weyl nodes are located very close to the Fermi level with the minimal trivial band density. A drumhead like surface state originating from a nodal loop around Y-point in the Brillouin zone is observed. A large value of the simulated anomalous Hall conductivity (1265 $\Omega^{-1} cm^{-1}$) indirectly reflects the topological non-trivial behavior of this compound. Such co-existent quantum phenomena are not common in condensed matter systems and hence it opens up a fertile ground to explore and achieve newer functional materials.