Programme

O.3 -- Oral

Date: Friday, 24 November 2017

Time: 14:15 - 14:35

Electronic, thermoelectric and magnetic properties of rare-earth doped bismuth telluride: First-principles density-functional theory calculation

Tran Van Quang

Department of Physics, University of Transport and Communications, No. 3, Lang Thuong, Hanoi, Vietnam

In this talk, we briefly introduce density functional theory (DFT) and its practical application to study the electronic structures and thermoelectric and magnetic properties of rare-earths doped bismuth telluride, Bi2Te3. By employing the precise full-potential linearized augmented plane wave (FLAPW) method, we report the effect of cerium and gadolinium substitutions in Bi2Te3 on the electronic, magnetic, and transport properties. The rare-earth substitutions lead to a new ternary compounds with f-states localized deeply from Fermi energy which purely determine the magnetic property of the formed compound. While CeBiTe3 shows metallic feature in the paramagnetic phase, the density of state at Fermi level reduces substantially leading the compound to be a very narrow energy band gap semiconductor in the spin-polarized phase. In the same fashion, the gadolinium substitution also leads to a similar ternary compound, i.e. GdBiTe3, showing many peculiar properties of which the metal-insulator transition is occurred under a cross-plane strain. The Hubbard parameters, U and J invoked in DFT+U implementation, do not alter the conclusion on the phase transition. To elaborate the transport properties, we performed calculations of thermoelectric transport coefficients by utilizing the semi-classical Boltzmann transport equation in a constant relaxation-time approximation. Results showed a drastic reduction of the Seebeck coefficient thereby the thermopower factor of the new formed compounds.

Presenter: Tran Van Quang