In solids, the kinetic energy of an
electron generally increases as the square of its momentum. By contrast, in a
Topological Insulator such as Bi2Te2Se, electrons on the surface are
predicted to be Dirac Fermions for which the energy increases linearly with
momentum. In a magnetic field B, the
allowed states of an electron are quantized into Landau Levels (LLs). The
sequential emptying of occupied LLs in an increasing field leads to quantum
oscillations in the conductance Gxx (Fig. 1A).