Electronic structure of YTiO3 and the charge transport through small polaron hopping

Iflah Laraib (U Delaware)

Dec 09. 2019, 16:10 — 16:30

Abstract: Rare-earth titanate YTiO3 is a prototype Mott insulator, with potential application in complex-oxide heterostructures. The description of its electronic structure has been quite challenging to density functional theory (DFT) calculations within standard (semi)local approximations to the exchange-correlation term. Recent calculations based on DFT+U and hybrid functionals have indicated that the band gap is significantly larger than previously reported values. The onset of optical excitations in YTiO3 is reported to be at about 0.6 eV [1] and the theoretical Mott-Hubbard gap using first principles calculations with hybrid functionals is reported to be around 2.07 eV [2]. Here we test the performance of the meta-GGA SCAN functional in the description of the electronic structure of YTiO3, comparing the results of hybrid functional and photoemission measurements. We carry out a detailed analysis of the effects of the TiO6 octahedral tilt and rotations, and lattice distortions on the Mott-Hubbard gap. We also study the formation of small hole polaron, its stability and migration, and compare them with measurements of resistivity as a function of temperature and Seebeck coefficient. References: [1] Kovaleva, N. N., Boris, A. V., Yordanov, P., Maljuk, A., BrĂ¼cher, E., Strempfer, J., Konuma, M., Zegkinoglou, I., Bernhard, C., Stoneham, A. M., Keimer, B., Optical response of ferromagnetic YTiO3 studied by spectral ellipsometry, Phys. Rev. B, 76 (2007), 155125. [2] Himmetoglu, B., Janotti, A.,Bjaalie, L., Van de Walle, C. G., Interband and polaronic excitations in YTiO3 from first principles, Phys. Rev. B, 90 (2014), 161102.

Further Information
ESI Boltzmann Lecture Hall
Associated Event:
Polarons in the 21st Century (Workshop)
Jozef Devreese (U Antwerpen)
Cesare Franchini (U of Vienna)
Georg Kresse (U of Vienna)
Jacques Tempere (U Antwerpen)