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Thickness dependence of electron-electron interactions in topological p−n junctions

Dirk Backes, Danhong Huang, Rhodri Mansell, Martin Lanius, Jörn Kampmeier, David Ritchie, Gregor Mussler, Godfrey Gumbs, Detlev Grützmacher, and Vijay Narayan
Phys. Rev. B 99, 125139 – Published 25 March 2019
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  • INTRODUCTION
  • EXPERIMENT
  • RESULTS
  • DISCUSSION
  • ACKNOWLEDGMENTS
    • Supplemental Material
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    Abstract

    Electron-electron interactions in topological p−n junctions consisting of vertically stacked topological insulators are investigated. n-type Bi2Te3 and p-type Sb2Te3 of varying relative thicknesses are deposited using molecular beam epitaxy and their electronic properties measured using low-temperature transport. The screening factor is observed to decrease with increasing sample thickness, a finding which is corroborated by semiclassical Boltzmann theory. The number of two-dimensional states determined from electron-electron interactions is larger compared to the number obtained from weak antilocalization, in line with earlier experiments using single layers.

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    • Received 1 December 2018

    DOI:https://doi.org/10.1103/PhysRevB.99.125139

    ©2019 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Topological insulators
    1. Physical Systems
    Narrow band gap systems
    1. Techniques
    Boltzmann theoryResistivity measurements
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    Dirk Backes1,2,*, Danhong Huang3, Rhodri Mansell1, Martin Lanius4, Jörn Kampmeier4, David Ritchie1, Gregor Mussler4, Godfrey Gumbs5, Detlev Grützmacher4, and Vijay Narayan1,†

    • 1Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
    • 2Department of Physics, Loughborough University, Epinal Way, Loughborough LE11 3TU, United Kingdom
    • 3Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117, USA
    • 4Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
    • 5Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065, USA

    • *db639@cam.ac.uk
    • †vn237@cam.ac.uk

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    Issue

    Vol. 99, Iss. 12 — 15 March 2019

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    Images

    • Figure 1
      Figure 1

      Comparison of the number of 2D channels from WAL (nWAL) and EEI (nEEI) as a function of the layer thickness. The values are taken from literature, with the references given in brackets. The bars indicate the spread between nEEI (top) and nWAL (bottom). Squares indicate experiments where nEEI=nWAL. The widths of the bars are proportional to the screening factor F (see scale bar at the bottom right).

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    • Figure 2
      Figure 2

      (a)–(d) Sheet resistance Rs dependance on temperature for four different samples. The arrows indicate the transition temperature T*. Inset in (a): Transition temperature T* dependence on thickness of the Sb2Te3 layer.

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    • Figure 3
      Figure 3

      (a)–(d) Longitudinal conductivity σxx of four different samples at low temperature for three different perpendicular magnetic fields. Using a logarithmic scale for the temperature, the linear regions are fitted using Eq. (1) (straight lines). The magnetic field leads to a change of slope, from which the screening and number of 2D channels can be derived.

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    • Figure 4
      Figure 4

      (a) Difference of conductivity correction δσ between 5 K and base temperature as a function of the Sb2Te3 thickness. (b) Change of the slope f with an external, perpendicular magnetic field, as shown in Fig. 3. (c) The screening factor F calculated from f=n(1−3/4*F), assuming the number of 2D states n is 1 (black squares) or 2 (red circles). The screening is negative for n=1 and between 0 and 1 for n=2, supporting the presence of more than one 2D channel. (d) Number of 2D channels α from WAL, obtained as described in the text. A value of 0.5 corresponds to one 2D channel.

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