paper

A Gapless MoS $_{2}$ Allotrope Possessing Both Massless Dirac and Heavy Fermions

arXiv:1401.7721 · doi:10.1103/PhysRevB.89.205402

Abstract

MoS $_{2}$ , a member of transition metal dichalcogenides (TMDs), recently emerged as one of the fastest growing two-dimensional materials due to its fascinating mechanical, thermal, electronic and optical properties. Unlike graphene which possesses massless Dirac fermions with ultra-high electron mobility, monolayer MoS $_{2}$ is a direct band gap semiconductor. An interesting question arises: Can monolayer MoS $_{2}$ also possess massless Dirac fermions with ultra-high electron mobility? Here, using first-principles calculations, we show that a monolayer MoS $_{2}$ allotrope, which consists of repeated square-octagon rings (abbreviated as so-MoS $_{2}$ to distinguish from the normal hexagonal lattice, h-MoS $_{2}$ ) possesses both massless Dirac fermions and heavy fermions. Distinct from the $p$ -orbital Dirac fermions of graphene, the Dirac fermions of so-MoS $_{2}$ are $d$ -electrons and possess Fermi velocity comparable to that of graphene. The Dirac cone structure in so-MoS $_{2}$ demonstrated here greatly enriches our understanding on the physical properties of TMDs and opens up new possibilities for developing novel electronic/spintronic devices.

9 pages, 4 figures

A Gapless MoS2​ Allotrope Possessing Both Massless Dirac and Heavy Fermions

Abstract

A Gapless MoS $_{2}$ Allotrope Possessing Both Massless Dirac and Heavy Fermions