Stability of the antiferromagnetic state in the electron doped iridates

Abstract

Iridates such as SrIrO are of considerable interest owing to the formation of the Mott insulating state driven by a large spin-orbit coupling. However, in contrast to the expectation from the Nagaoka theorem that a single doped hole or electron destroys the anti-ferromagnetic (AFM) state of the half-filled Hubbard model in the large U limit, the anti-ferromagnetism persists in the doped Iridates for a large dopant concentration beyond half-filling. With a tight-binding description of the relevant [Formula: see text] states by the third-neighbor (t , t, t , U) Hubbard model on the square lattice, we examine the stability of the AFM state to the formation of a spin spiral state in the strong coupling limit. The third-neighbor interaction t is important for the description of the Fermi surface of the electron doped system. A phase diagram in the parameter space is obtained for the regions of stability of the AFM state. Our results qualitatively explain the robustness of the AFM state in the electron doped iridate (such as Sr La IrO), observed in many experiments, where the AFM state continues to be stable until a critical dopant concentration.

Electronic structure and optical properties of Sr2IrO4 under epitaxial strain

“…An important feature of the band structure is the occurrence of the conduction minimum at the M point of the Brillouin zone, which the electrons would occupy in the electron doped system. It can be easily shown that for this to happen, the TB parameters must satisfy the condition [7] t t t U 2 , A . 1 0…”

“…It has been suggested that the spin-orbital entanglement induced by the strong SOC in these structures could make these materials hosts for several unconventional features such as the Kitaev model [2,3], quantum spin Hall effect at room temperature [4], or unconventional superconductivity [5,6]. In addition, doped carriers in the spin-orbital entangled Mott insulating state in the iridates are expected to show many novel features and are also the subject of several recent studies [7][8][9][10].…”

Implications of electron and hole doping on the magnetic properties of spin–orbit entangled Ca4IrO6 from DFT calculations

“…However, according to the Nagaoka theorem, a minimal amount of carrier doping can destroy the antiferromagnetic state within a nearest neighbor model [9]. However, an analysis of the stability of the antiferromagnetic state for electron-doped * Electronic address: NGanguli@iiserb.ac.in iridates within Hartree-Fock approximation and secondorder perturbation theory reveals the persistence of antiferromagnetic states for small doping concentration [10]. With 1% doping of carriers, Sr 2 IrO 4 is found to exhibit a metallic state, suggesting a decrease in energy gap with increasing carrier concentration [11].…”

Intra- and inter-orbital correlated electron spin dynamics in $\rm Sr_2 Ir O_4$: spin-wave gap and spin-orbit exciton

“…The effectively single (pseudo) orbital (J=1/2) nature of this Mott insulator has motivated intensive finite doping studies aimed at inducing the superconducting state as in the cuprates. [4][5][6][7][8][9][10] Recent technological advancements in resonant inelastic X-ray scattering (RIXS) have been instrumental in the elucidation of the pseudospin dynamics in Sr 2 IrO 4 . In the first published data, 11 spectra along high-symmetry directions in the Brillouin zone reveal a single gapless spin-wave mode with a dispersion of ∼200 meV, indicating isotropic nature of pseudo-spin interactions.…”