Coexistence of topological nontrivial and spin-gapless semiconducting behavior in MnPO4: A composite quantum compound

Composite quantum compounds (CQC) are classic example of quantum materials\nwhich host more than one apparently distinct quantum phenomenon in physics.\nMagnetism, topological superconductivity, Rashba physics etc. are few such\nquantum phenomenon which are ubiquitously observed in several functional\nmaterials and can co-exist in CQCs. In this letter, we use {\\it ab-initio}\ncalculations to predict the co-existence of two incompatible phenomena, namely\ntopologically non-trivial Weyl semimetal and spin gapless semiconducting (SGS)\nbehavior, in a single crystalline system. SGS belong to a special class of\nspintronics material which exhibit a unique band structure involving a\nsemiconducting state for one spin channel and a gapless state for the other. We\nreport such a SGS behavior in conjunction with the topologically non-trivial\nmulti-Weyl Fermions in MnPO$_4$. Interestingly, these Weyl nodes are located\nvery close to the Fermi level with the minimal trivial band density. A drumhead\nlike surface state originating from a nodal loop around Y-point in the\nBrillouin zone is observed. A large value of the simulated anomalous Hall\nconductivity (1265 $\\Omega^{-1} cm^{-1}$) indirectly reflects the topological\nnon-trivial behavior of this compound. Such co-existent quantum phenomena are\nnot common in condensed matter systems and hence it opens up a fertile ground\nto explore and achieve newer functional materials.\n