Quantum Oscillations in a Topological Insulator Bi$_2$Te$_2$Se with Large Bulk Resistivity (6 $\Omega$cm)

Understand

We report the observation of prominent Shubnikov-de Haas oscillations in a Topological Insulator, Bi$_2$Te$_2$Se, with large bulk resistivity (6 $\Omega$cm at 4 K).

• By fitting the SdH oscillations, we infer a large metallicity parameter $k_F\ell$ = 41, with a surface mobility ($\mu_s\sim$ 2,800 cm$^2$/Vs) much larger than the bulk mobility ($\mu_b\sim$ 50 cm$^2$/Vs).
• The plot of the index fields $B_{\nu}$ vs.
• filling factor $\nu$ shows a $\frac12$-shift, consistent with massless, Dirac states.