Abstract

Low-dimensional phases possessing protection of transport
from undesirable effects of material imperfections attract
evergrowing attention of physicists. One possibility of
such protection is provided by the so-called helicity of
electrons. Helicity means lock-in relation between the momentum
and the spin of an electron. It can suppress backscattering and,
thus, protects ballistic transport. In this talk, I will
address helical phases in magnetically doped nanowires. The
appropriate theoretical model for these systems is a dense
one-dimensional Kondo lattice (KL). The KL consists of itinerant
electrons interacting with localized quantum magnetic moments.
The main focus will be on the phase diagram of magnetically
isotropic KLs. The spin rotation symmetry prohibits the origin
of the global helicity, which extends over the entire sample
and is inherent in all previously studied helical systems. I
will demonstrate, that even a local helicity suffices for the
protection of transport, find conditions, under which it emerges,
and discuss possible experimental tests.

1. A.M. Tsvelik and O.M. Yevtushenko, “Quantum Phase Transition
and Protected Ideal Transport in a Kondo Chain”, PRL 115,
216402 (2015).

2. A.M. Tsvelik and O.M. Yevtushenko, “Physics of arbitrarily
doped Kondo lattices: From a commensurate insulator to a
heavy Luttinger liquid and a protected helical metal”, PRB 100,
165110 (2019).

3. A.M. Tsvelik and O.M. Yevtushenko, “Transport in magnetically
doped one-dimensional wires: can the helical protection emerge
without the global helicity?”, New J. Phys. 22 053013 (2020).