Observation of Volkov-Pankratov states in topological HgTe heterojunctions using high-frequency compressibility

Abstract

It is well established that topological insulators sustain Dirac fermion surface states as a consequence of band inversion in the bulk. These states have a helical spin polarization and a linear dispersion with large Fermi velocity. In this article we report on a set of experimental observations indicating the existence of massive surface states. These states are confined at the interface and dominate equilibrium and transport properties at high energy and/or high electric field. By monitoring the AC admittance of HgTe topological insulator field-effect capacitors, we access the compressibility and conductivity of surface states in a broad range of energy and electric fields. The Dirac surface states are characterized by a compressibility minimum, a linear energy dependence and a high mobility persisting up to energies much larger than the transport bandgap of the bulk. New features are revealed at high energies with signatures such as conductance peaks, compressibility bumps, a strong charge metastability and a Hall resistance anomaly. These features point to the existence of excited massive surface states, responsible for a strong intersubband scattering with the Dirac states and the nucleation of metastable bulk carriers. The spectrum of excited states agrees with predictions of a phenomenological model of the topological-trivial semiconductor interface. The model accounts for the finite interface depth and the effect of electric fields. The existence of excited topological states is essential for the understanding of topological phases and opens a route for engineering and exploiting topological resources in quantum technology.

arXiv comment29 pages, 8 figures

References in corpus (28)

• Topological insulators and superconductors
• Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
• Quantum Spin Hall Insulator State in HgTe Quantum Wells
• Topological Insulators in Three Dimensions
• A topological Dirac insulator in a quantum spin Hall phase : Experimental observation of first strong topological insulator
• Discovery of a Weyl Fermion Semimetal and Topological Fermi Arcs
• First observation of Spin-Momentum Helical Locking in Bi2Se3 and Bi2Te3, demonstration of Topological-Order at 300K and a realization of topological-transport-regime
• Recent developments in transport phenomena in Weyl semimetals
• Quantum transport of massless Dirac fermions in graphene
• Quantum Hall Effect from the Topological Surface States of Strained Bulk HgTe
• Coexistence of the topological state and a two-dimensional electron gas on the surface of Bi2Se3
• $4\pi$-periodic Josephson supercurrent in HgTe-based topological Josephson junctions
• Quantized Faraday and Kerr rotation and axion electrodynamics of a 3D topological insulator
• Band structure of semimagnetic Hg1-yMnyTe quantum wells
• Novel electric field effects on Landau levels in Graphene
• Gapless Andreev bound states in the quantum spin Hall insulator HgTe
• Emergent quantum confinement at topological insulator surfaces
• Observation of the universal magnetoelectric effect in a 3D topological insulator
• Two-dimensional surface charge transport in topological insulators
• Josephson radiation from gapless Andreev bound states in HgTe-based topological junctions
• Transport properties of a 3D topological insulator based on a strained high mobility HgTe film
• Boosting Majorana zero modes
• Probing quantum capacitance in a 3D topological insulator
• Volkov-Pankratov states in topological heterojunctions
• Magnetic description of the Fermi arc in type-I and type-II Weyl semimetals
• Transport scattering time probed through rf admittance of a graphene capacitor
• Self-consistent $\text{k}\cdot \text{p}$ calculations for gated thin layers of 3D Topological Insulators
• RF-quantum capacitance of the topological insulator Bi2Se3 in the bulk depleted regime for field-effect transistors

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