Evidence of Electronic Phase Separation in the Strongly Correlated Semiconductor YbB12

Abstract

We investigate high-quality single-domain crystals of YbB12 using the precise x-ray diffraction technique in combination with the low-temperature polarized THz–infrared spectroscopy and accurate magnetotransport measurements. It is shown for the first time that this archetypal strongly correlated system with a metal-insulator transition to a mysterious dielectric ground state with a metal Fermi surface [Science 362, 65 (2018) and ibid 362, 32 (2018)] is actually a heterogeneous compound in the regime of electronic phase separation. Changes in the configuration of the discovered dynamic charge stripes are proposed upon cooling. As a result, a conclusion is drawn in favor of a crossover between different patterns of the filamentary electronic structure penetrating the semiconducting matrix of YbB12. We argue that the discovery of stripes in YbB12 is fundamental, elucidating the nature of exotic dielectric state in Kondo insulators.