Residual gas absorption effect on the electronic structure of Cr-doped Bi2Se3

Abstract

In this report, we identify the origin of the temperature dependence of the surface energy gap in impurity-doped topological insulators. The gap at the Dirac point and its variation with temperature were studied by using angle-resolved photoemission spectroscopy in Cr-doped Bi2Se3. Our valence band photoemission results revealed that the gap varies with temperature due to residual gas condensation on the sample surface with cooling. Adsorbate on the surface of the sample creates an electron doping effect that modifies the chemical potential of the system resulting in the change of the gap with variable temperature. Such electron doping can weaken the ferromagnetism and lead to a bulk band contribution in the transport measurements. Also, a larger energy gap is required to suppress the thermal excitations for the quantum anomalous Hall effect. Therefore, such effects can hinder the quantum anomalous Hall state at higher temperatures. Resolving this issue can pave the way for enhancing the observation temperature of the quantum anomalous Hall effect. Therefore, our findings can play a significant role in the discovery of the high-temperature quantum anomalous Hall effect in impurity-doped topological insulators.

8 pages, 6 figures

References in corpus (10)

• Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
• Experimental Observation of the Quantum Anomalous Hall Effect in a Magnetic Topological Insulator
• Phase transition between the quantum spin Hall and insulator phases in 3D: emergence of a topological gapless phase
• High-precision realization of robust quantum anomalous Hall state in a hard ferromagnetic topological insulator
• Rapid Surface Oxidation as a Source of Surface Degradation Factor for Bi2Se3
• Emergent quantum confinement at topological insulator surfaces
• Unexpected mass acquisition of Dirac fermions at the quantum phase transition of a topological insulator
• Tailoring Magnetic Doping in the Topological Insulator Bi2Se3
• Nonmagnetic band gap at the Dirac point of the magnetic topological insulator (Bi${}_{1-x}$Mn${}_x{)}_2$Se${}_3$
• Chemical potential dependent gap-opening at the Dirac surface states of Bi2Se3 induced by aggregated substitutional Cr atoms