Investigation Of Anisotropic Pi Plasmon Induced By The Intrinsic Crystallographic Defects In Topological Crystalline Insulator Material-Tin-Substitutional Lead Selenide (Pb1-Xsnxse)

The presence of intrinsic defects in topological crystalline insulator materials has been predicted to improve the thermoelectric figure-of-merit values in the literature. Performing atomic-resolved high angle annular dark field imaging, momentum-resolved electron energy loss spectroscopy, and electron spectroscopic diffraction, we observed those intrinsic defects, including interstitial Se atoms and Se vacancies, to cause localized mirror symmetry breaking and further result in the anisotropic pi -plasmon dispersion along theGamma X overbar mml:mover andGamma M mml:mo overbarmml:mover directions in single-crystal Pb1-xSnxSe (x=0 and 0.34). In addition to the anisotropic pi plasmon dispersion, the splitting lines along themml:mover accent="true"Gamma X mml:mo mml:mover direction were revealed with selected pi plasmon energy in the electron spectroscopic diffraction pattern.