Tuning the metal-insulator transition in d1 and d2 perovskites by epitaxial strain: A first-principles-based study

Abstract

We investigate the effect of epitaxial strain on the Mott metal-insulator transition (MIT) in perovskite systems with d 1 and d 2 electron configuration of the transition metal (TM) cation. We first discuss the general trends expected from the changes in the crystal-field splitting and in the hopping parameters that are induced by epitaxial strain. We argue that the strain-induced crystalfield splitting generally favors the Mott-insulating state, whereas the strain-induced changes in the hopping parameters favor the metallic state under compressive strain and the insulating state under tensile strain. Thus, the two effects can effectively cancel each other under compressive strain, while they usually cooperate under tensile strain, in this case favoring the insulating state. We then validate these general considerations by performing electronic structure calculations for several d 1 and d 2 perovskites, using a combination of density functional theory (DFT) and dynamical mean-field theory (DMFT). We isolate the individual effects of strain-induced changes in either hopping or crystal-field by performing DMFT calculations where we fix one type of parameter to the corresponding unstrained DFT values. These calculations confirm our general considerations for SrVO3 (d 1 ) and LaVO3 (d 2 ), whereas the case of LaTiO3 (d 1 ) is distinctly different, due to the strong effect of the octahedral tilt distortion in the underlying perovskite crystal structure. Our results demonstrate the possibility to tune the electronic properties of correlated TM oxides by using epitaxial strain, which allows to control the strength of electronic correlations and the vicinity to the Mott MIT. arXiv:1608.03523v1 [cond-mat.str-el]

Metal-insulator transition in CaVO3 thin films: Interplay between epitaxial strain, dimensional confinement, and surface effects

“…2d. They exhibit the same trends that have already been observed in similar systems [20]. The epitaxial stain induces a tetragonal-like splitting between the three t 2g -MLWFs that depends approximately linear on the strain, with one orbital at higher and two orbitals at lower energies under strong compressive strain, and vice versa under strong tensile strain.…”

“…Under compressive strain, this additonal splitting is small and vanishes completely below −4 % strain, due to the suppression of the out-of-plane tilts which raises the symmetry of the system to tetragonal. Further, we note that the nearest neighbor hopping amplitudes exhibit a similar strain dependence to what has been reported previously for related systems [20]. Next, we investigate whether epitaxial strain facilitates the formation of a Mott-insulating state in CaVO 3 , by performing DMFT calculations within the correlated subspace defined in the MLWF basis, as described in Sec.…”

Tuning of the Optical Properties of the Transparent Conducting Oxide SrVO3 by Electronic Correlations

“…Such interplay between the electronic and optical properties via the electronic correlations may also open a new way for the optimization of the functional properties of SVO. In strongly correlated metals, it is known that strain may influence the correlation characteristics via the related crystal distortions, which were also predicted theoretically for SVO . In a strongly correlated TCO as SVO, it may therefore be possible to not only influence the electrical transport by strain, but also the optical properties.…”

Correlated Lattice Instability and Emergent Charged Domain Walls at Oxide Heterointerfaces

“…It is known that the conduction band of STO is formed by Ti 3 d t 2g orbitals . The hopping amplitude of t 2g electrons, or the conduction band width w , is determined by the overlap integral between Ti 3d t 2g and O 2p orbitals in TiO 6 octahedra . A semiempirical relationship has been built to estimate w in 3d perovskite ABO 3 oxide with w ≈ cos[(π−θ)/2]/ d 3.5 , where θ is the B–O–B bond angle and d is the B–O bond length .…”