Tunneling into the Mott insulatorSr2IrO4

Abstract

The single-layer Mott insulator Sr2IrO4 was studied using a scanning tunneling microscope. This measurement technique is unique due to the transport properties of this Mott insulator allowing tunneling measurements to be performed, even at cryogenic temperatures. We obtained high-resolution images of the sample surface and the differential tunneling conductance at different cryogenic temperatures. The differential conductance is a direct measurement of the local electronic density of states which provided an insulating gap consistent with optical conductivity, angle resolved photoemission spectroscopy and resonant inelastic x-ray scattering (RIXS) experiments. The observed widths of these features is broader than predicted by the Slater approximation and narrower than predicted by dynamical mean field theory. Additionally, the observed density of states due to magnetic fluctuations is found in the derivative of the differential conductance and is consistent with results from Raman scattering and RIXS. At low temperatures, additional low-energy features were observed, suggesting a change in the dispersion of the collective magnetic excitations, which is consistent with the magnetic susceptibility.

Theoretical study of insulating mechanism in multiorbital Hubbard models with a large spin-orbit coupling: Slater versus Mott scenario inSr2IrO4

“…The insulating gap of ∼ 0.62 eV estimated from the scanning tunneling microscopy/spectroscopy (STM/STS) is unusually large for a Slater-type insulator and claimed to be a Mott gap. 77,78 On the other hand, the temperature dependence of the gap below T N seems to be consistent with the Slater-type behavior, [49][50][51][52] although the pseudogaplike behavior above T N should be discussed in more detail. Moreover, the time-resolved photocarrier dynamics experiment suggests that Slater and Mott characteristics coexist in Sr 2 IrO 4 .…”

Evidence of quantum dimer excitations inSr3Ir2O7

“…This can be illustrated by considering the end members of this series. Single-layer Sr 2 IrO 4 (n = 1) is an insulator ( E ≈ 615 meV [4]) with a canted, basalplane antiferromagnetic (AF) ground state [5,6], displaying a magnon dispersion [7] consistent with an effective Hamiltonian dominated by Heisenberg interactions, in agreement with theory [8]. SrIrO 3 (n = ∞) is a strongly correlated metal with ferromagnetic correlations [9].…”

Influence of electron doping on the ground state of(Sr1−xLax)2IrO4

“…Undoped, the SOM parent state of Sr 2 IrO 4 manifests a robust charge gap of E G ≈ 600 meV 7,8 and an antiferromagnetically ordered ground state 9 . Charge transport data within this state shows a localized, tunneling form of conduction, which correlates to three-dimensional variable range hopping (VRH) at low temperatures 10,11 .…”