Transport and topological properties of ThOCh(Ch: S, Se and Te) in bulk and monolayer: a first principles study.

The present study unveils the topological insulating nature of Th-based oxy-chalcogenides and their transport properties which are less explored. A systematic analysis of electronic, topological, mechanical, dynamical and thermoelectric properties of ThOCh (Ch: S, Se and Te) in bulk and monolayer is presented. The effect of spin-orbit coupling is found to be appreciable in ThOTe compared to ThOS and ThOSe, causing a strong topological nature in bulk ThOTe.

Quantum fluctuation in thermopower at the topological phase transition in CaSrX (X: Si, Ge, Sn, Pb) studied from first principles theory.

The present density functional calculations propose the compounds CaSrX (X: Si, Ge, Sn, Pb) as strong topological insulators, with appreciable thermoelectric properties. Emergence of Dirac semi-metallic states has been observed in CaSrX (X: Si, Ge, Sn, Pb), which is induced by uni-axial strain along 'b' axis. CaSrSi and CaSrGe evolved as normal semiconductors with uni-axial strain.

Giant thermopower in 'p' type OsX (X: S, Se, Te) for a wide temperature range: a first principles study.

We report the electronic structure and thermoelectric (TE) properties of OsX (X: S, Se, Te), and find a giant value of thermopower of magnitude 600 μV K-800 μV K for a wide temperature range of 100 K-500 K for hole doping (at 10 cm), which is higher than the value found for well established TE materials. The optimized structural parameters are in good agreement with available experimental reports. The mechanical stability of all the compounds are confirmed from the computed elastic constants.

ZnGeSb: a promising thermoelectric material with tunable ultra-high conductivity.

First principles calculations predict the promising thermoelectric material ZnGeSb with a huge power factor (Sσ/τ) on the order of 3 × 10 W m K s, due to the ultra-high electrical conductivity scaled by a relaxation time of around 8.5 × 10 Ω m s, observed in its massive Dirac state. The observed electrical conductivity is higher than the well-established Dirac materials, and is almost carrier concentration independent with similar behaviour of both n and p type carriers, which may certainly attract device applications.