Modulation of Dirac electrons in epitaxial Bi2Se3 ultrathin films on van der Waals ferromagnet Cr2Si2Te

Abstract

We investigated the Dirac-cone state and its modulation when an ultrathin film of topological insulator Bi 2 Se 3 was epitaxially grown on a van der Waals ferromagnet Cr 2 Si 2 Te 6 (CST) by angle-resolved photoemission spectroscopy. We observed a gapless Dirac-cone surface state in six quintuple-layer (6QL) Bi 2 Se 3 on CST, whereas the Dirac cone exhibits a gap of 0.37 eV in its 2QL counterpart. Intriguingly, this gap is much larger than those for Bi 2 Se 3 films on Si(111). We also revealed no discernible change in the gap magnitude across the ferromagnetic transition of CST, suggesting the very small characteristic length and energy scale of the magnetic proximity effect. The present results suggest a crucial role of interfacial coupling for modulating Dirac electrons in topological-insulator hybrids.

Orbital contributions in the element-resolved valence electronic structure of Bi2Se3

“…Nonetheless, Bianchi et al tuned the k z of Bi 2 Se 3 by varying the incidence photon energies and successfully differentiated the bulk and surface electronic states near the Fermi level [12]. Some ARPES experiments were carried out by using a laser source of 6 ∼ 7 eV [13,14] or Xe lamp of 8.4 eV [15][16][17][18], which can enhance depth sensitivity, but the purpose was to improve the intensity and k resolution for studying the physics of Dirac cone, which is beyond the scope of our work. Hard x-ray photoemission spectroscopy (HAXPES) extends the probing depth and is more sensitive to the bulk electronic structure.…”