Nanoscale physics

Electron interaction-driven peculiarities of strongly correlated system thermopower 
Kramar O., Dovhopyaty Yu., Skorenkyy Yu.
Ternopil Ivan Puluj National Technical University, 56 Ruska St, Ternopil, Ukraine. 
E-mail: skorenkyy.tntu@gmail.com

Peculiar thermoelectric properties of narrow-band materials suggest their use  for energy harvesting and other high-demand technologies. In particular, studies of the layered cobaltites [1] and weakly electron-doped titanates [2] reveal thermopower values much larger than those typical for semiconductors. Interpreting these peculiarities requires a detailed characterization of band structure and electron correlations in these perspective materials. Recently, some progress has been achieved [3] in understanding of the temperature dependence of electron contribution to thermopower in materials with narrow energy bands. In the present work we make use of the theoretical model of electron subsystem for strongly correlated compound with a peculiar density of electronic states (DOS). The energy spectrum has been calculated within the unperturbative approach [4, 5]. The chemical potential and Seebeck coeficient have been calculated numerically for a number of realistic DOS forms for non-integer band fillings. Distinct types of Seebeck coefficient temperature bechavior has been attributed to different electron interaction regimes to be realised in some regions of electron band-filling and strongly influenced by the DOS form.

1.	Terasaki I., Sasago Y., Uchinokura K. Large thermoelectric power in NaCo2O4 single crystals // Phys. Rev. B. - 1997.- 56. - P.R12685-R12687.
2.	Okuda T., Nakanishi K., Miyasaka S., Tokura Y. Large thermoelectric response of metallic perovskites: Sr1-xLaxTiO3 // Phys. Rev. B. - 2001. - 63. - 113104. 
3.	Shastry B.S. Thermopower in Correlated Systems. In: Zlatic V., Hewson A. (eds) New Materials for Thermoelectric Applications: Theory and Experiment.  Physics and Biophysics. Springer, Dordrecht. -2013. - P. 25-29. 
4.	Didukh L., Kramar O., Skorenkyy Yu., Dovhopyaty Yu. Magnetic field dependence of of conductivity and effective mass of carriers in a model of Mott-Hubbard material // Condens. Matter Phys. - 2005. - 8, N 4. - P. 825-834.
5.	Skorenkyy Yu., Kramar O., Dovhopyaty Yu. Electron-hole asymmetry in electron systems with orbital degeneracy and correlated hopping // Condens. Matter Phys. - 2020. - 23, N 4. - 43714.