Hallmarks of the Mott-metal crossover in the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4

Abstract

The physics of doped Mott insulators remains controversial after decades of active research, hindered by the interplay among competing orders and fluctuations. It is thus highly desired to distinguish the intrinsic characters of the Mott-metal crossover from those of other origins. Here we investigate the evolution of electronic structure and dynamics of the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4. The effective hole doping is achieved by replacing Ir with Rh atoms, with the chemical potential immediately jumping to or near the top of the lower Hubbard band. The doped iridates exhibit multiple iconic low-energy features previously observed in doped cuprates—pseudogaps, Fermi arcs and marginal-Fermi-liquid-like electronic scattering rates. We suggest these signatures are most likely an integral part of the material's proximity to the Mott state, rather than from many of the most claimed mechanisms, including preformed electron pairing, quantum criticality or density-wave formation.

Electron and hole doping in the relativistic Mott insulator Sr2IrO4 : A first-principles study using band unfolding technique

“…It was proposed that Ir→Rh chemical substitution leads to hole-transfer from Rh to Ir ideally leading to the formation of Ir 5+ and Rh 3+ ions [17,21,22]. While formally correct, this picture is rather simplified as it does not consider possible changes in the Ir-d/O-p hybridization and does not account for the presence of the two inequivalent Ir I and Ir II sites in the compound (see Fig.…”

“…Among the different forms of electron and hole doping tested in this system, the most studied ones are the substitution of Sr 2+ with La 3+ (electron doping) and the homovalent heterosubstitution of 5d 5 Ir 4+ with 4d 5 Rh 4+ (effective hole doping) [15,[17][18][19][20][21][22][23][24][25][26]. In one of the first studies, Lee and coworkers conducted a systematic investigation of La, Rh, and Ru doping in Sr 2 IrO 4 by means of optical spectroscopy and found that the J eff = 1/2 state remains spectroscopically robust upon doping and that in all cases doping induces an insulator-to-metal transition (IMT) for moderately low dopant concentrations (≈ 5%) [19].…”

Anisotropic softening of magnetic excitations in lightly electron-dopedSr2IrO4

“…The 5d oxide Sr 2 IrO 4 is an excellent candidate for such study. This so called spin-orbit-coupling driven Mott insulator [3] is in close proximity to the single layered cuprate La 2 CuO 4 , both structure-wise [4] and electronically [5][6][7][8]. Sr 2 IrO 4 hosts a single hole in the t 2g manifold where a Mott gap is opened, assisted by strong spin-orbit coupling [3,9,10], and its magnetic excitation spectrum can be well described using a Heisenberg model of effective spin-1 2 moments on a square lattice [11,12].…”

Low-energy model and electron-hole doping asymmetry of single-layer Ruddlesden-Popper iridates

“…Second, investigating the low-energy k-space differentiation also exposes a doping asymmetry, taking place at weaker as well as at stronger coupling and has partly already been confirmed by recent experiments. 16,17 Fermi-surface pockets that occur for weaker electron-electron interaction are more likely for hole doping, whereas Fermi arcs may set in for stronger interaction with higher tendency again on the electron-doped side. Therefore electrondoped iridates are candidates for a possible analogue to hole-doped cuprates.…”

“…[16][17][18][19][20][21] By surface electron doping of Sr 2 IrO 4 , 16 the quasiparticle (QP) strength seems to vary along the Fermi surface, somehow reminiscent of the famous Fermi arcs known from holedoped cuprates. Though effective hole-doping of Sr 2 IrO 4 also shows k-selective features, 17 but the fermiology appears much more incoherent.…”