Knight shift anisotropy as a function of charge doping in a Mott insulator with strong spin-orbit coupling*

We present a detailed analysis of NMR powder spectral patterns of the double perovskite Ba2Na1-xCaxOsO6 (0 < x < 1), a charge doped Mott insulator with strong spin-orbit coupling (SOC). The analysis of the spectra in the low temperature exotic quantum phases across the entire doping range reveals anisotropy in the local susceptibility. The physics implication on the nature of these low temperature phases will be discussed.