A new spin on doped Mott insulators
Prof. Ilija Zeljkovic
Department of Physics, Boston College
A Mott insulator, a material characterized by the localization of electrons due to strong electron-electron interactions, is typically accompanied by magnetic ordering. Charge carrier doping can gradually suppress this insulating state, but despite decades of research, it is still unclear how the co-existent magnetic order melts with doping at the nanoscale. We use spin-polarized scanning tunneling microscopy (SP-STM) to visualize the antiferromagnetic order in doped Mott insulators Sr2IrO4 and Sr3Ir2O7. We find that near insulator-to-metal transition, the long-range antiferromagnetic order melts into a fragmented state with short-range correlations. Moreover, the static short-range antiferromagnetic order is locally uncorrelated with the spectral gap magnitude, reigniting the discussion of origin of electronic inhomogeneity in doped iridates. Interestingly, we find that thermal cycling leads to a spatial reorganization of some magnetic domains, indicating possible multiple stable configurations as the material undergoes the magnetic transition.
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