First-principles calculation of spin and orbital contributions to magnetically ordered moments in Sr2IrO4

Abstract

We show how an accurate first-principles treatment of the canted-antiferromagnetic ground state of Sr2IrO4, a prototypical 5d correlated spin-orbit coupled material, can be obtained without invoking any free parameters such as the Hubbard U or tuning the spin-orbit coupling strength. Our theoretically predicted iridium magnetic moment of 0.250 µB, canted by 12.6 • off the a-axis, is in accord with experimental results. By resolving the magnetic moments into their spin and orbital components, we show that our theoretically obtained variation of the magnetic scattering amplitude Mm as a function of the polarization angle is consistent with recent non-resonant magnetic x-ray scattering measurements. The computed value of the band gap (55 meV) is also in line with the corresponding experimental values. A comparison of the band structure to that of the cuprates suggests the presence of incommensurate charge-density wave phases in Sr2IrO4.

Interpretations of ground-state symmetry breaking and strong correlation in wavefunction and density functional theories

“…"Strong correlation" is sometimes used to mean "everything that DFT gets wrong." Yet, hybrid functionals (including part of the Hartree-Fock exchange) like HSE06 (8-10) (for nonmetallic states) and meta-generalized gradient approximations (meta-GGAs) like the strongly constrained and appropriately normed (SCAN) functional (4,(11)(12)(13)(14)(15)(16)(17)(18) are yielding quantitatively correct ground-state (and we emphasize "ground-state") results by symmetry breaking for some systems that have long been regarded as strongly correlated. In the cuprate high-temperature superconducting materials, for example, the SCAN meta-GGA (4) is able to do what simpler density functionals (local spin density approximation [LSDA] and generalized gradient approximation [GGA]) cannot (13), by creating the correct spin moments on the copper atoms, their antiferromagnetic order, and a correctly nonzero band gap in the undoped material that correctly disappears under the doping that also leads to superconductivity (12)(13)(14).…”

Subtle metastability of the layered magnetic topological insulator MnBi2Te4 from weak interactions

“…Since 11 meV/atom is comparable to the finite temperature contributions to the reaction free energy from the electronic, magnetic, and vibrational degrees of freedom, PBE will falsely predict that MnBi 2 Te 4 cannot be synthesized below its melting temperature, even in a metastable phase. In addition to the vdW interaction, it is likely that SCAN + rVV10 more accurately describes the d electrons of Mn (and hence the magnetic properties of MnTe and MnBi 2 Te 4 ) when compared to PBE, due to the reduced self-interaction errors, a result demonstrated by previous studies on many other transition metal compounds 25,26,[29][30][31][32][33][34][35][36][37][38] .…”

f-Electron and Magnetic Ordering Effects in Nickelates LaNiO2 and NdNiO2: Remarkable Role of The Cuprate-Like 3dx2-y2 Band

“…hole Fermi surface appears surrounding Γ near the k z = 0 plane, along with the formation of electron pockets near M . We further note that the narrow neck of the goblet Fermi surface at Γ suggests that the system is close to a Fermi surface topological transition where the goblet splits into Fermi pockets centered on the Z point [ Fig Electronic structure of G-AFM Phase: While the C-AFM phase is found to be the ground state, it is important to study other low-lying phases in correlated quantum materials that could contribute to various intertwined orders [36,37,[41][42][43]. between Ni 3d z 2 and Nd 4f orbitals at Γ point (blue) [ Fig.…”

“…In this article, we present a systematic study of the electronic and magnetic structures of both LaNiO 2 and NdNiO 2 using the strongly-constrained-appropriatelynormed (SCAN) density functional [35] with spin-orbit coupling to examine effects of the f -electron physics. The SCAN functional has a proven track record of accurately modeling many correlated materials families including the cuprates [36][37][38][39][40], iridates [41], and ABO 3 materials [42]. In particular, SCAN accurately predicts the f -band splitting in SmB 6 in good accord with experimental values [43].…”