Title:	Ab initio calculations of magnetism and transport in Ce heavy-fermion compounds
DNr:	SNIC 2014/1-327
Project Type:	SNIC Medium Compute
Principal Investigator:	Leonid Poyurovskiy <leonid@cpht.polytechnique.fr>
Affiliation:	Linköpings universitet
Duration:	2014-10-31 – 2015-11-01
Classification:	10304
Keywords:

Abstract

This project will be continuation of the work started under snic001-11-125, snic001-12-160, SNIC 001/12-195 and snic-2013/1-226 in investigating properties of correlated transition-metal and rare-earth-based compounds with an advanced first-principles theoretical method based on the dynamical mean-field theory (DMFT). In the framework of those previous projects we have calculated the properties of different phases of iron as well as Ce-based heavy fermion materials. The work on transition metals resulted in several publications clarifying the role of electronic correlations in the physics of Fe and its alloys at extreme conditions: Pourovskii ... Ekholm et al. Phys. Rev. Lett. 110, 117206 (2013), Pourovskii et al. Phys. Rev. B 87, 115130 (2013), Pourovskii et al. arXiv:1312.3654 (accepted to Phys. Rev. B), Vekilova, Pourovskii et al. arXiv:1410.0596 (2014). The project on Ce-based heavy-fermion has also resulted in several publications, concerning, in particular, theoretical prediction of an orbital transition in the CeM2X2 heavy-fermion superconductors (Pourovskii et al. Phys. Rev. Lett. 112, 106407 (2014), Zen, Pourovskii et al. Phys. Rev. X 4, 031055 (2014) ), and the of Kondo scale in CeNiAsO under pressure ( Luo, Pourovskii et al., Nature Materials 13, 777 (2014)). In the framework of the present project we plan to continue the work on the CeM2X2 family of heavy-fermion compounds, in particular, to study their transport and magnetic properties and to explore the impact of the previously predicted orbital transition on those properties. The temperature dependence of resistivity in several CeM2X2 (CeCu2Si2, CeCu2Ge2, CeAu2Si2) features two characteristic peaks, with the low-temperature one shifting to higher temperatures under applied pressure to finally merge with the high-temperature one at the pressure corresponding to the maximum of the superconducting region on the phase diagram. The nature of this peculiarities in the resistivity and their apparent connection to the non-conventional superconductivity observed in CeM2X2 has not been elucidated to date. The measured magnetic susceptibility in those compounds cannot been explained on the basis of a standard simple picture of quasi-atomic Ce 4f levels split by a crystal field. Ab initio study of those properties will be essential to unrevealing the complex physics of CeM2X2. Hence, we plan to employ the first-principles DMFT approach to compute the electron-electron-scattering contribution to resistivity as well as the uniform magnetic susceptibility of several CeM2X2 compounds on a pressure-temperature grid and elucidate their dependence on the orbital occupancies.