Angle resolved photoemission spectroscopy study on electronic band structure of topological insulator Bi_2Se_3 in the presence of magnetic impurities

摘要

As magnetic ordering in topological insulators (Tis) can break the time reversal symmetry (TRS), the Tis are predicted to openup a band gap at the Dirac point in presence of magnetic impurities. To experimentally observe the effect of magnetic impurities on the electronic structure, we have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) experiments on 3D Ti Bi_2Se_3 along with various magnetically doped compounds such as Co_(0.1)Bi_2Se_3, Mn_(0.1)Bi_2Se_3 and Eu_(0.1)Bi_(1.9)Se_3. Though no band gap opening at the Dirac point was observed due to very small amount of doping, a clear shift of Dirac point to higher binding energy was observed. Our measurements show the presence of conducting surface and insulatingbulk states for all the compounds and also indicate that all the magnetic elements we doped in Bi_2Se_3 provide additional electrons to the compound which eventually causes shift of the Dirac point.