Robustness of Rashba and Dirac Fermions against Strong Disorder

Abstract

By addressing the interplay between substitutional disorder and spin-orbit-coupling in chalcogenide alloys, we predict a strong robustness of spectral features at the Fermi energy. Indeed, supplementing our state of the art first-principles calculations with modeling analysis, we show that the disorder self-energy is vanishingly small close to the band gap, thus i) allowing for bulk Rashba-like spin splitting to be observed in ferroelectric alloys by means of Angle Resolved PhotoEmission Spectroscopy, and ii) protecting the band-character inversion related to the topological transition in recently discovered Topological Crystalline Insulators. Such a protection against strong disorder, which we demonstrate to be general for three dimensional Dirac systems, has potential and valuable implications for novel technologies, as spintronics and/or spinorbitronics.

Topological Tuning in Three-Dimensional Dirac Semimetals

“…As shown in Ref. [19], this is a consequence of a vanishing disorder self-energy around the crossing point. We also propose that a similar phase transition, and a similar robustness against disorder, would occur in the Cd 3 ðAs 1−x P x Þ 2 alloy, since the parent compounds Cd 3 As 2 and Cd 3 P 2 are Dirac semimetal and conventional insulator, respectively, with the former having an inverted band order and the latter having a normal band sequence (see Supplemental Material [30]).…”

“…We note, in fact, the absence of broadening of spectral features around the cone, as compared to other energies. Such a robustness, similar to what happens for topological crystalline insulators and Weyl fermion systems, arises from the three-dimensional nature of the Dirac cone [19], and in turn leads to the concrete possibility of experimental verifications by means of spectroscopic techniques. As shown in Ref.…”

“…By combining this scheme with a coherent potential approximation (CPA) including self-energy corrections for disorder, we have investigated the Na 3 Bi 1−x Sb x alloy [18]. We note that this methodology has been recently used to predict the robustness of Dirac fermions in topological crystalline insulator (TCI) alloys, as well as in ferroelectric Rashba semiconductor (FERSC) alloys [19].…”

Intertwined Rashba, Dirac, and Weyl Fermions in Hexagonal Hyperferroelectrics

“…[10] It is worth noting that such a phase is protected against the broadening effects of disorder, as a natural consequence of the three dimensional nature of its electronic structure. [26] Furthermore, the distinct power law of the density of states within the Weyl phase (i.e., D(ω) ∝ ω 2 ) leads to a change of exponents in the temperature dependence of thermodynamic quantities such as the specific heat (C V ∼ T 3 ) and compressibility (κ ∼ T 2 ) [29], making this phase easily discernable by means of thermodynamics measurements. Moreover, we argue that the chirality of any Weyl fermion is electrically switchable by reversing the ferroelectric polarization.…”

“…In this energy region, the three dimensional nature of the Weyl fermions' dispersion ensures protection against the renormalisation effects of disorder. [26] The finite bandwidth is only due to a finite δ = 10 meV in the Green's function calculation. [25] ing from the unique interplay with ferroelectricity.…”