Bulk metals with helical surface states

Abstract

In the flurry of experiments looking for topological insulator materials, it has been recently discovered that some bulk metals very close to topological insulator electronic states, support the same topological surface states that are the defining characteristic of the topological insulator. First observed in spin-polarized ARPES in Sb (D. Hsieh et al. Science 323, 919 (2009)), the helical surface states in the metallic systems appear to be robust to at least mild disorder. We present here a theoretical investigation of the nature of these "helical metals" - bulk metals with helical surface states. We explore how the surface and bulk states can mix, in both clean and disordered systems. Using the Fano model, we discover that in a clean system, the helical surface states are \emph{not} simply absorbed by hybridization with a non-topological parasitic metallic band. Instead, they are pushed away from overlapping in momentum and energy with the bulk states, leaving behind a finite-lifetime surface resonance in the bulk energy band. Furthermore, the hybridization may lead in some cases to multiplied surface state bands, in all cases retaining the helical characteristic. Weak disorder leads to very similar effects - surface states are pushed away from the energy bandwidth of the bulk, leaving behind a finite-lifetime surface resonance in place of the original surface states.

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• Observation of Topological Superconductivity in a Stoichiometric Transition Metal Dichalcogenide 2M-WS2
• Topologically protected surface states in a centrosymmetric superconductor beta-PdBi2
• Anomalous Hall Effects of Light and Chiral Edge Modes on the Kagome Lattice
• Local invariants identify topology in metals and gapless systems
• Topological protection of bound states against the hybridization
• Fermi-Level Pinning, Charge Transfer, and Relaxation of Spin-Momentum Locking at Metal Contacts to Topological Insulators
• An operator-based approach to topological photonics
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• Hybridization-induced interface states in a topological insulator-magnetic metal heterostructure
• Observation of a bulk 3D Dirac multiplet, Lifshitz transition, and nestled spin states in Na3Bi
• Topological response theory of doped topological insulators
• Topological metal behavior in GeBi2Te4 single crystals
• The Coexistence and Decoupling of Bulk and Edge States in Disordered Two-dimensional Topological Insulators
• Axion response in gapless systems
• Effects of surface-bulk hybridization in 3D topological `metals'
• Topological insulators in random potentials
• Surface-state spin textures in strained bulk HgTe: strain-induced topological phase transitions
• Non-adiabatic bulk-surface oscillations in driven topological insulators
• Disordered topological metals
• Transport through a disordered topological-metal strip
• Absence of helical surface states in bulk semimetals with broken inversion symmetry
• Unconventional topological phase transition from semimetal to insulator in SnBi2Te4: Role of anomalous thermal expansion
• Electron dynamics in topological insulator based semiconductor-metal interfaces (topological p-n interface based on Bi2Se3 class)
• A non-perturbative expression for the transmission through a leaky chiral edge mode
• Topological Surface Superconductivity Induced by Hydrostatic Pressure-Enhanced Antisymmetric Spin-Orbit Coupling in Non-Centrosymmetric Superconductor PbTaSe2
• First Principles Prediction of Topological Phases in Thin Films of Pyrochlore Iridates
• Magnetically induced spin reorientation on the surface of a topological insulator (a surface magnetic topological insulator MBE film)
• Weak ${\mathbb{Z}}_2$ Supertopology