Transport in Magnetically Doped One-Dimensional Wires: Can the Helical Protection Emerge without the Global Helicity?

Abstract

We study the phase diagram and transport properties of arbitrarily doped quantum wires functionalized by magnetic adatoms. The appropriate theoretical model for these systems is a dense one-dimensional Kondo Lattice (KL) which consists of itinerant electrons interacting with localized quantum magnetic moments. We discover the novel phase of the locally helical metal where transport is protected from a destructive influence of material imperfections. Paradoxically, such a protection emerges without a need of the global helicity, which is inherent in all previously studied helical systems and requires breaking the spin-rotation symmetry. We explain the physics of this protection of the new type, find conditions, under which it emerges, and discuss possible experimental tests. Our results pave the way to the straightforward realization of the protected ballistic transport in quantum wires made of various materials.

Protected helical transport in magnetically doped quantum wires: Beyond the one-dimensional paradigm

“…In the opposite case T K < E RKKY , the RKKY interaction dominates and governs inter-impurity correlations. One can translate the above inequality to distances and show that RKKY overwhelms the Kondo effect in dense KCs, where the (mean) inter-impurity distance ξ s is smaller than a crossover scale ξ c : ξ s ≤ ξ c ∝ ξ 0 ρ 0 J 2 /T K 1/2 [30][31][32][33]. Here J, ρ 0 , and ξ 0 are the Kondo coupling, the density of states, and the lattice spacing, respectively.…”

“…Another promising platform for protected helical transport is provided by magnetically doped 1D quantum wires [30][31][32][33]. It is somewhat similar to the successful realization of topological superconductivity [34][35][36].…”

“…The RKKY dominated regime is typical in 1D systems [32,52]. Two of us have recently shown that the (partially) protected transport can exist in the dense and incommensurate KC with a small Kondo coupling, which can be anisotropic (easyplane anisotropy) [30,31] or isotropic [32,33]. In both cases, protection of transport results from the (global or local) helicity of localized spins.…”

“…The physics of the dense KCs is governed by backscattering of the fermions [30][31][32][33] described by…”

“…k νν F = kF for the interband backscattering, ν = −ν , and k νν F = kF + νδk F /2 for the intraband one, ν = ν . Backscattering opens a gap in the spectrum of fermions and, thus, reduces the ground state energy of the entire system [30][31][32][33].…”