Dimensionality-controlled Mott transition and correlation effects in single-layer and bilayer perovskite iridates

Abstract

11We studied Sr 2 IrO 4 and Sr 3 Ir 2 O 7 using angle-resolved photoemission spectroscopy (ARPES), making direct 12 experimental determinations of intra-and inter-cell coupling parameters as well as Mott correlations and gap sizes.

Excitonic quasiparticles in a spin–orbit Mott insulator

“…While such a sharp peak is not uncommon in RIXS spectra of iridates 29 , it is certainly much narrower than that of the sharpest peak (B200 meV) in the hole spectral function measured by ARPES for the same material 13,30 . The peak width is also much smaller than its total bandwidth (E112 meV), which establishes the exciton as a propagating mode in a solid, or a QP.…”

Carrier localization and electronic phase separation in a doped spin-orbit-driven Mott phase in Sr3(Ir1–xRux)2O7

“…Furthermore, in concentrations doped close to the MIT, the recovery of the ordered AF moment to values nearly equalling that of the undoped parent Sr 3 Ir 2 O 7 rules out any trivial superposition of chemically distinct phases. A magnetically ordered, metallic state beyond the MIT is reminiscent of the phase diagrams of (Ca 1 À x Sr x ) 3 25,26 . The global picture our data provide shows that the physics here is more complex than that of a trivially diluted AF system with 3 Ir 2 O 7 in regions with enhanced LDOS due to oxygen defects (yellow curves) and spectra collected away from defects showing the full charge gap (red curves).…”

“…A magnetically ordered, metallic state beyond the MIT is reminiscent of the phase diagrams of (Ca 1 À x Sr x ) 3 25,26 . The global picture our data provide shows that the physics here is more complex than that of a trivially diluted AF system with 3 Ir 2 O 7 in regions with enhanced LDOS due to oxygen defects (yellow curves) and spectra collected away from defects showing the full charge gap (red curves). We note here that the inhomogeneity observed within the parent insulating system stems from relatively rare regions of oxygen defects and that the majority of the surface showed fully gapped behaviour (red curves), whereas for the x ¼ 0.35 and x ¼ 0.5 systems the entirety of the samples showed strong electronic inhomogeneity across nanometre-length scales.…”

“…Collimations of 30 0 -60 0 -33 0 -144 0 were used before the monochromator, sample, analyser and detector, respectively. The polarized neutron experiment was carried out on the BT7 triple-axis spectrometer at the NIST Center for Neutron Research using PG(002) monochromator, 3 He polarizers, PG filters before and after the sample, radial collimation and a position-sensitive detector on the scattered side. A guide field allowed the magnetic field to be tuned along the scattering vector (horizontal field) and perpendicular to the scattering plane (vertical field) configuration.…”

“…The resulting bandwidth-narrowed J eff ¼ 1/2 states allow the relatively modest U(B1.5-2 eV) inherent to these 5d-transition metal elements 3 to split the band and generate a charge gap. A SOC-assisted Mott phase results, allowing an unexpected manifestation of correlationdriven physics in materials with extended 5d-electron wave functions.…”