High-Temperature Quantum Anomalous Hall Effect inn−pCodoped Topological Insulators

Abstract

The quantum anomalous Hall effect (QAHE) is a fundamental quantum transport phenomenon that manifests as a quantized transverse conductance in response to a longitudinally applied electric field in the absence of an external magnetic field, and promises to have immense application potentials in future dissipation-less quantum electronics. Here we present a novel kinetic pathway to realize the QAHE at high temperatures by n-p codoping of three-dimensional topological insulators. We provide proof-of-principle numerical demonstration of this approach using vanadium-iodine (V-I) codoped Sb2Te3 and demonstrate that, strikingly, even at low concentrations of ∼2% V and ∼1% I, the system exhibits a quantized Hall conductance, the tell-tale hallmark of QAHE, at temperatures of at least ∼ 50 Kelvin, which is three orders of magnitude higher than the typical temperatures at which it has been realized so far. The proposed approach is conceptually general and may shed new light in experimental realization of high-temperature QAHE. Two-dimensional electron systems (2DESs) are versatile playgrounds for complex quantum transport phenomena that are of interest both from fundamental and application points of view. One prominent example is the quantum Hall effect (QHE) [1, 2], a quantum analogue of the classical Hall effect, whereby the application of a magnetic field to a 2DES results in the quantization of the transverse conductance and a vanishing longitudinal conductance. Crucially, the mechanisms underlying this phenomenon are the formation of an insulating bulk and remarkable chiral conducting edge states (Fig. 1a). This striking unidirectionality makes backscattering impossible, and renders transport along these edge states remarkably robust against any impurities [3,4]. This robustness essentially renders the edges of 2DESs manifesting the QHE as perfectly conducting one-dimensional (1D) wires, which would be of great interest as potential building blocks, such as interconnects between chips, in dissipation-less electronics. However, a major constraint for practical use of this fundamental quantum transport phenomenon is the requirement of very strong magnetic fields, which is impractical for realistic applications.Realizing the quantum anomalous Hall effect (QAHE) would circumvent this problem because it manifests the same hallmark features as the QHE, but does not require the application of an external magnetic field [5]. The reason why the QAHE does not require the application of an external field is because the latter's role is played by an intricate cooperation between the intrinsic magnetism that breaks the time-reversal symmetry and spin-orbit coupling in the 2D (quasi-2D) insulating host material. Initial proposals for realizing the QAHE were based on honeycomb lattice models [5]. Since then, especially after the experimental discoveries of graphene (with an inherent honeycomb lattice structure) [6] and topological insulators (TIs) [7,8], much effort has been made to exploring new platforms for realizing QAHE in th...

Topological Insulator Film Growth by Molecular Beam Epitaxy: A Review

“…MBE-grown films have a number of advantages over exfoliated films, including large area growth and the ability to controllably dope the materials, resulting in recent observations of the quantum anomalous Hall effect [22][23][24][25][26][27]. Unfortunately, both bulk crystals and thin films tend to exhibit significant conductivity from non-topological electrons, either from bulk states and/or from surface accumulation layers [28,29].…”

Magnetic proximity coupling to Cr-doped Sb2Te3 thin films

“…Most notably the quantum anomalous Hall effect (QAHE), a fundamental quantum transport phenomenon, has been observed [6]. It is thought that this effect will be the key to unlocking major advancements in dissipationless quantum electronics [7]. The breaking of TRS can be achieved through two different methods, which result in the application of a magnetic field: via proximity to a ferromagnetic layer, or by achieving magnetic long-range order in the TI by doping (e.g., with Fe [8], Mn [9], or Cr [10]).…”

Quantum anomalous Hall effect in ferromagnetic transition metal halides

“…This was first predicted by Haldane [8]. Subsequently, some 2D materials, such as transition metal (TM) doped TIs [9][10][11], TM decorated graphene [12,13], Rashba spin-orbit coupling and exchange field induced silicene [14,15], TM based organometallic frameworks [16,17], heavy element layers [18], p-band optical systems [19], noncollinear antiferromagnetic K 0.5 RhO 2 layer [20], and semi-functionalized stanene or germanene [21], are theoretically predicted to possess QAH effect. In these materials, the spin-orbit coupling (SOC) opens a global band gap at the Fermi level, resulting in topologically nontrivial insulating property.…”