Inducing n - and p -Type Thermoelectricity in Oxide Superlattices by Strain Tuning of Orbital-Selective Transport Resonances

Abstract

By combining first-principles simulations including an on-site Coulomb repulsion term and Boltzmann theory, we demonstrate how the interplay of quantum confinement and epitaxial strain allows to selectively design nand p-type thermoelectric response in (LaNiO3)3/(LaAlO3)1(001) superlattices. In particular, varying strain from −4.9 to +2.9 % tunes the Ni orbital polarization at the interfaces from −6 to +3 %. This is caused by an electron redistribution among Ni 3d x 2 −y 2 -and 3d z 2 -derived quantum well states which respond differently to strain. Owing to this charge transfer, the position of emerging cross-plane transport resonances can be tuned relative to the Fermi energy. Already for moderate values of 1.5 and 2.8 % compressive strain, the cross-plane Seebeck coefficient reaches ∼ −60 and +100 µV/K around room temperature, respectively. This provides a novel mechanism to tailor thermoelectric materials. Finally, we explore the robustness of the proposed concept with respect to oxygen vacancy formation. arXiv:1812.00503v2 [cond-mat.mtrl-sci]

Correlated interface electron gas in infinite-layer nickelate versus cuprate films on SrTiO$_3$(001)

“…Higher-level methods are beyond the scope of the present work due to the large system sizes [30,31]. Static correlation effects were considered within the DFT+U formalism [32,33] employing U = 4 eV on Ni, Cu, and Ti sites, in line with previous work [9,[34][35][36][37][38]. We confirmed that a higher value of U Cu = 6.5 eV [39] leads to largely identical results.…”

Adsorption and dissociation of iron phthalocyanine on H/Si(111): Impact of van der Waals interactions and perspectives for subsurface doping

“…We also explored the more recent many-body dispersion (MBD) technique [32], in which the atomic response functions are represented by quantum harmonic oscillators and the screened long-range many-body vdW energy is computed from the adiabatic connection fluctuation dissipation theorem within the dipole approximation. Constant-current STM images at a bias voltage V were simulated subsequently in the spirit of Tersoff and Hamann [47] as 0 -isosurfaces of the integrated local density of states (ILDOS) [12,[48][49][50][51]…”

Coupling of electronic and structural degrees of freedom in vanadate superlattices

“…For comparison, typical energy differences for quenching or altering the a − a − c + octahedral rotation pattern in YVO bulk are of the order of several hundreds of meV per Vion. Moreover, canceling the octahedral rotations in the less tilted LaNiO 3 /LAO(001) SLs requires 250-300 meV per transition metal ion [20,68]. Fig.…”

“…In this context, simulations in the framework of density functional theory including a Hubbard-U term (DFT+U ), provide valuable insights. In particular, these calculations have successfully explained the orbital polarization profiles of charge-transfer systems such as heterostructures of nickelates [16][17][18][19][20][21][22] and cuprates [18,23]. * E.Benckiser@fkf.mpg.…”