Proposed detection of time-reversal symmetry in topological surface states

By employing the T-matrix approach, we investigate a nonmagnetic impurity located on the surface of three-dimensional topological insulators, where the time-reversal symmetry is preserved. It is shown that the images of the local density of states (LDOS) around the single impurity have dip-hump structures with six-fold symmetry at different bias voltages. The peaks are produced by quasiparticle interference, while the local minima at the backscattering wave vectors are due to the absence of backscatterings. With increasing the bias voltage, the peaks and dips move forward to the location of the impurity. These dips at the backscattering wave vectors in the LDOS spectra can be regarded as a signature of the time-reversal symmetry in the topological surface states, which can be observed by scanning tunneling microscopy.