Research teams from University of Central Florida, Princeton Univeristy and Los Alamos National Laboratory explain the significance and science behind their work into new topological semi-metals.

Dirac materials are of high research interest because they provide possible ground for exploring free relativistic fermions and exhibit exotic properties like extreme magnetoresistance. The property of a material, which causes the change in electrical resistance when a magnetic field is applied to it, is called magnetoresistance. Recently, the family of rare earth monopnictides (MX, where M = Lanthanides, Yt and Sc, and X = N, P, As, Bi, Sb) with a NaCl-like simple crystal structure are predicted to possess topological Dirac semi-metallic phase with extreme magnetoresistance (XMR). Furthermore, the presence of a f -electron in this system makes them potential candidates for exhibiting a strongly correlated electronic state. However, a detailed experimental electronic structure of this system has not yet been reported.

Experimental observation of Dirac-like fermions in NdSb. © 2016 IOP Publishing Ltd.

For the first time, using a angle-resolved photoemission spectroscopy technique, Professor Madhab Neupane’s group at the University of Central Florida together in collaboration with Princeton University and Los Alamos National Laboratory (LANL) reported a systematic electronic structure study of NdSb (a member of this family). The experimental data, published in JPCM, reveal the existence of multiple Fermi pockets (two hole pockets at the zone center Γ point and two electron like pockets at the corner (X) point of the Brillouin zone). Importantly, a linearly dispersive Dirac-like band at around the X point of the Brillouin zone is observed, where the Dirac point is located at 370 meV below the Fermi level.

Rare earth monopnictides with XMR have great potential for applications in spintronics, switches, magnetic sensors, memory devices etc. This work will open up a new platform to study the Dirac semi-metallic state in other members of this monopnictide family. Apart from this, Professor Neupane’s research focuses mainly on the electronic and spin properties of new quantum materials, such as correlated topological insulators, Dirac, Weyl and nodal semimetals, topological Kondo insulators, topological crystalline insulators, and two-dimensional materials investigated using angle-, spin- and time-resolved photoemission techniques.

This work is licensed under a Creative Commons Attribution 3.0 Unported License. Image taken from Madhab Neupane et al 2016 J. Phys.: Condens. Matter 28 23LT02 © 2016 IOP Publishing Ltd.

Categories: Journal of Physics: Condensed Matter

Tags: Condensed matter physics, Dirac, Guest blog, Magnetoresistance, Rare-earth materials, Semi-metals