Evidence of Electronic Phase Separation in the Strongly Correlated Semiconductor YbB_(12)

We investigate high-quality single-domain crystals of YbB_(12)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 YbB_(12).We argue that the discovery of stripes in YbB_(12)is fundamental,elucidating the nature of exotic dielectric state in Kondo insulators.