Turning a Nickelate Fermi Surface into a Cupratelike One through Heterostructuring

Abstract

Using the local density approximation and its combination with dynamical mean-field theory, we show that electronic correlations induce a single-sheet, cuprate-like Fermi surface for hole-doped 1/1 LaNiO3/LaAlO3 heterostructures, even though both eg orbitals contribute to it. The Ni 3d 3z 2 −1 orbital plays the role of the axial Cu 4s-like orbital in the cuprates. These two results indicate that "orbital engineering" by means of heterostructuring should be possible. As we also find strong antiferromagnetic correlations, the low-energy electronic and spin excitations in nickelate heterostructures resemble those of high-temperature cuprate superconductors. PACS numbers: 71.27.+a, 71.10.Fd, 74.78.Fk The discovery of high-temperature superconductivity (HTSC) in hole-doped cuprates [1] initiated the quest for finding related transition-metal oxides with comparable or even higher transition temperatures. In some systems such as ruthenates [2] and cobaltates [3] superconductivity has been found. However, in these t 2g systems superconductivity is very different from that in cuprates and transition temperatures (T c 's) are considerably lower.As it became possible to grow transition-metal oxides in heterostructures, this quest got a new direction: Novel effectively two-dimensional (2D) systems could be engineered. But which oxides, besides cuprates, are most promising for getting high T c 's?The basic band structure of the hole-doped cuprates is that of a single 2D Cu 3d x 2 −y 2 -like band which is less than half-filled (configuration d 9−h ). In this situation, antiferromagnetic fluctuations prevail and are often believed to mediate the superconductivity. The Fermi surface (FS) from this x 2 − y 2 band has been observed in many overdoped cuprates and found to agree with the predictions of density-functional (LDA) band theory.Recently the following idea for arriving at a cupratelike situation in nickelates was presented [4]: Bulk LaNiO 3 d 7 has one electron in two degenerate e g bands, but sandwiching a LaNiO 3 layer between layers of an insulating oxide such as LaAlO 3 will confine the 3z 2 − 1 orbital in the z-direction and may remove this band from the Fermi level, thus leaving the electron in the x 2 − y 2 band. The possibility of finding bulk nickelates with an electronic structure analogous to that of cuprates was discarded a while ago [5], but heterostructures offer new perspectives.Indeed, a major reconstruction of orbital states at oxide interfaces may recently have been observed [6], and this kind of phenomenon could lead to novel phases not present in the bulk. Extensive theoretical studies of mechanisms for orbital selection in correlated systems [7] have revealed the complexity of this problem, where details of the electronic structure and lattice distortions play decisive roles. It is therefore crucial to examine nickelate heterostructures by means of state-of-the-art theoretical methods and find the optimal conditions for x 2 − y 2 orbital selection.In this Letter we present results of electronic-str...

Spin-moment formation and reduced orbital polarization in LaNiO3/LaAlO3superlattice:LDA+UHan1, Veenendaal2 2012Phys. Rev. B224182View full textAdd to dashboardCite

“…From the single-site DMFT calculations with a double-counting energy as another tuning parameter, Wang et al 21 showed that there is a well defined N c , that is, the critical value of d-valency of transition metal; the system is metallic if Relative orbital occupation in the two e g orbitals is a central quantity in understanding LNO/LAO systems 9,12,14,15 . The orbital polarization can be nonzero due to the translation symmetry breaking induced by heterostructuring while the bulk polarization is 0.…”

“…Since previous calculations were performed at the LDA 14 or DMFT level 12,15 and assumed the bulk-like PM phase, LDA+U calculation can provide meaningful information especially regarding the magnetism in this system. Our total energy calculations showed that the Ni spins order ferromagnetically within the LNO layer, and the inter-layer couplings are also ferromagnetic (FM).…”

“…A series of recent theoretical studies have created considerable interest, suggesting the heterostructuring-induced orbital polarization and the possible high-T c superconductivity in LaNiO 3 (LAO)/LaAlO 3 (LAO) superlattice 12,17 . In this picture, the two degenerate Ni e g orbital states are split by a combination of translational symmetry breaking and on-site Coulomb interaction, leading to a cuprate-like band structure.…”

“…One of the most intriguing classes of materials may be the nickelate superlattices [9][10][11][12][13][14][15][16] . A series of recent theoretical studies have created considerable interest, suggesting the heterostructuring-induced orbital polarization and the possible high-T c superconductivity in LaNiO 3 (LAO)/LaAlO 3 (LAO) superlattice 12,17 .…”

Towards ab initio Calculations with the Dynamical Vertex Approximation

“…Already the first DFT+DMFT calculations allowed for a better understanding of the Mott-Hubbard transition in V 2 O 3 , 22) of δ-Pu, 23) the Ce volume collapse, 22) and magnetism in Fe and Ni. 24) More recently, among others, iron pnictides and their fluctuating magnetic moment, [25][26][27] complex oxide heterostructures, [28][29][30][31][32] nanoscopic structures, 33,34) thermoelectricity, [35][36][37] spin-orbit interactions, 38,39) and electronic entanglement 40) have been addressed.…”