Electrical, Thermal and Spectroscopic Characterization of Bulk Bi2Se3 Topological Insulator

We report the electrical (angular magnetoresistance and Hall), thermal (heat capacity) and spectroscopic (Raman, X-ray photoelectron, angle-resolved photoelectron) characterization of a bulk Bi2Se3 topological insulator, which was grown by self-flux method through solid-state reaction from high-temperature (950. degrees C) melt and slow cooling (2. degrees C/h) of constituent elements. Bi2Se3 exhibited metallic behaviour down to 5 K. Magnetotransport measurements revealed linear up to 400 and 30% magneto-resistance (MR) at 5 K under a 14-T field in perpendicular and parallel field directions, respectively. We noticed that the MR of Bi2Se3 is very sensitive to the angle of the applied field. The MR is maximum when the field is normal to the sample surface, while it is minimum when the field is parallel. The Hall coefficient (RH) is seen nearly invariant with a negative carrier sign down to 5 K albeit having near-periodic oscillations above 100 K. The heat capacity (C-p) versus temperature plot is seen without any phase transitions down to 5 K and is well fitted (Cp =gamma T + beta T-3) at low temperature with a calculated Debye temperature (theta(D)) value of 105.5 K. Clear Raman peaks are seen at 72, 131 and 177 cm(-1) corresponding to A(1g)(1), E-g(2) and A(1g)(2), respectively. Though two distinct asymmetric characteristic peak shapes are seen for Bi 4f(7/2) and Bi 4f(5/2), the Se 3d region is found to be broad, displaying the overlapping of spin-orbit components of the same. Angle-resolved photoemission spectroscopy (ARPES) data of Bi2Se3 revealed distinctly the bulk conduction bands (BCB), surface state (SS), Dirac point (DP) and bulk valence bands (BVB), and 3D bulk conduction signatures are clearly seen. Summarily, a host of physical properties for the as-grown Bi2Se3 crystal are reported here.