Probing Charge Order And Hidden Topology At The Atomic Scale By Cryogenic Scanning Transmission Electron Microscopy And Spectroscopy

Charge orders (COs) and entangled topology denote the fundamentals of correlated electron systems at low temperatures, and their profound revelation at atomic scale awaits experimental advances. Here, we report such a spatially resolved investigation using cryogenic atomic-scale electron microscopy and spectroscopy at 100 K, with the CO insulator of HgMn7O12 below 240 K as an exemplification. By the cryogenic technique, we can resolve the charge and lattice characteristics of the insulating CO phase at atomic resolution and identify the order parameters (OPs) at play as charge-density-modulated (similar to 31.4 angstrom, modulation length) and antiphase (similar to 10.5 angstrom) OPs. Both OPs are largely unaddressed forms of COs in correlated oxides and display the emergent topology of intertwining mesoscopic stripes of 10-40 nm in width and >= 500 nm in length, distinctly different from the atomically narrow CO stripes conventional to correlated systems and depicting the unique electronic contour of the phase. This preliminary demonstration of the cryogenic unveiling of the OPs and topological landscape paves the way to disentangling the multifarious COs and hidden topology in condensed matters and, meanwhile, calls for further developments in the atomic-scale cryogenic spectral probing at an enhanced speed.