Noncontact Mutual-Inductance-Based Measurement of an Inhomogeneous Topological Insulating State in Bi2Se3 Single Crystals with Defects

Abstract

Pure Topological Insulating materials preserve a unique electronic state comprising of * Email: satyajit@iitk.ac.in. ARPES data reproduced from Fig. 1 of M. Bianchi et al., Nature Comm. 1, 128 (2010) Dirac point K (Å -1 ) k F (~0.04 Å -1 )

Imaging current distribution in a topological insulator Bi2Se3 in the presence of competing surface and bulk contributions to conductivity

“…1 a shows a metallic behaviour of bulk resistivity ( ρ ) of the film measured as a function of increasing temperature ( T ). The unavoidable presence of intrinsic defects, like Se vacancies which electron dope the Bi 2 Se 3 film 23 , 27 lead to metallic conductivity in Bi 2 Se 3 . Inset of Fig.…”

“…The disorder induced bulk conduction in TI bulk (which is insulating in an ideal TI) opens up an additional conduction channel which is in parallel to the topological high conduction edge or surface state channel already present in TI’s. Recent bulk mutual inductance measurements in Bi 2 Se 3 27 , 28 shows a predominance of topological surface state conductivity at low T , however beyond 70 K the bulk contribution grows and competes with surface conductivity. The studies show that above 70 K the bulk conductivity is of a thermally activated nature 27 , 28 .…”

“…Recent bulk mutual inductance measurements in Bi 2 Se 3 27 , 28 shows a predominance of topological surface state conductivity at low T , however beyond 70 K the bulk contribution grows and competes with surface conductivity. The studies show that above 70 K the bulk conductivity is of a thermally activated nature 27 , 28 . In view of the above issues in TI related to transformation between surface and bulk contribution to conductivity, there have been few systematic imaging studies of current flow in 3D-TI over a wide temperature range.…”

Imaging current distribution in a topological insulator Bi2Se3 in the presence of competing surface and bulk contributions to conductivity

“…The crystal has dimensions of 1.9 mm × 0.9 mm × 0.02 mm. We have already investigated crystals from the same batch earlier using electrical transport [24] and two-coil mutual inductance techniques [27,28]. Mechanical exfoliation gave freshly cleaved flat surface of the Bi2Se3 crystal.…”

“…1a shows a metallic behaviour of bulk resistivity (ρ) of the film measured as a function of increasing temperature (T). The unavoidable presence of intrinsic defects, like Se vacancies which electron dope the Bi2Se3 film [23,27] lead to metallic conductivity in Bi2Se3. Inset of Fig.…”