Chemical Gating of a Weak Topological Insulator: Bi14Rh3I9

TL;DR

This study investigates chemical gating of Bi14Rh3I9, a weak topological insulator, using density functional calculations to address surface polarity issues that hinder experimental confirmation and potential device applications.

Contribution

The paper introduces chemical gating and counter-doping strategies via density functional calculations to neutralize surface polarity in Bi14Rh3I9, preserving its topological gap.

Findings

Surface polarity can be compensated without closing the electronic gap.

Chemical gating effectively shifts the Fermi level to confirm topological properties.

Density functional calculations support experimental topological character of Bi14Rh3I9.

Abstract

The compound Bi14Rh3I9 has recently been suggested as a weak three-dimensional topological insulator on the basis of angle-resolved photoemission and scanning-tunneling experiments in combination with density functional (DF) electronic structure calculations. These methods unanimously support the topological character of the headline compound, but a compelling confirmation could only be obtained by dedicated transport experiments. The latter, however, are biased by an intrinsic n-doping of the materials surface due to its polarity. Electronic reconstruction of the polar surface shifts the topological gap below the Fermi energy, which would also prevent any future device application. Here, we report the results of DF slab calculations for chemically gated and counter-doped surfaces of Bi14Rh3I9. We demonstrate that both methods can be used to compensate the surface polarity without closing the electronic gap.