Granular topological insulators

Abstract

Granular conductors form an artificially engineered class of solid state materials wherein the microstructure can be tuned to mimic a wide range of otherwise inaccessible physical systems. At the same time, topological insulators (TIs) have become a cornerstone of modern condensed matter physics as materials hosting metallic states on the surface and insulating in the bulk. However it remains to be understood how granularity affects this new and exotic phase of matter. We perform electrical transport experiments on highly granular topological insulator thin films of Bi${}_2$Se${}_3$ and reveal remarkable properties. We observe clear signatures of topological surface states despite granularity with distinctly different properties from conventional bulk TI systems including sharp surface state coupling-decoupling transitions, large surface state penetration depths and exotic Berry phase effects. We present a model which explains these results. Our findings illustrate that granularity can be used to engineer designer TIs, at the same time allowing easy access to the Dirac-fermion physics that is inaccessible in single crystal systems.

17 pages, 6 figures

References in corpus (22)

• Topological Insulators
• Topological insulators and superconductors
• Topological Insulators in Three Dimensions
• Topological Insulators with Inversion Symmetry
• Discovery (theoretical prediction and experimental observation) of a large-gap topological-insulator class with spin-polarized single-Dirac-cone on the surface
• Topological Field Theory of Time-Reversal Invariant Insulators
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• First direct observation of Spin-textures in Topological Insulators : Spin-resolved ARPES as a probe of topological quantum spin Hall effect and Berry's phase
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• Three dimensional topological invariants for time reversal invariant Hamiltonians and the three dimensional quantum spin Hall effect
• Model Hamiltonian for Topological Insulators
• Surface States of the Topological Insulator Bi_{1-x}Sb_x
• Experimental demonstration of the topological surface states protected by the time-reversal symmetry
• Granular Electronic Systems
• Competition between weak localization and antilocalization in topological surface states
• Landau quantization and the thickness limit of topological insulator thin films of Sb2Te3
• Weak Localization and Antilocalization in Topological Insulator Thin Films with Coherent Bulk-Surface Coupling
• Weak antilocalization in HgTe quantum wells and topological surface states: Massive versus massless Dirac fermions
• Parallel field magnetoresistance in topological insulator thin films
• Effects of surface-bulk hybridization in 3D topological `metals'
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