Colossal magnetoresistance in topological Kondo insulator

TL;DR

This paper demonstrates that a colossal magnetoresistance effect occurs in a topological Kondo insulator, where magnetic fields induce a metal-insulator transition through spin and fermion gap formation, revealing novel topological phases.

Contribution

It introduces a model of a topological Kondo lattice on a honeycomb lattice showing how hybridization leads to topological insulator states with chiral edge modes and explains the mechanism behind colossal magnetoresistance.

Findings

Magnetic field induces a gap in spin and fermion spectra.

System exhibits topological insulator states with chiral edge modes.

Hybridization between Majorana fermions explains the topological properties.

Abstract

Abnormal electronic properties of complex systems require new ideas concerning explanation of their behavior and possibility of realization. In this acticle we show that a colossal magnetoresistance is realized in the state of the topological Kondo insulator, that is similar to the Kondo insulator state in the Kondo lattice. The mechanism of the phenomenon is the following: in the spin gapless phase an external magnetic field induces the gap in the spectrum of spin excitations, the gap in the spectrum of fermions is opened due to a hybridization between spin and fermion subsystems at half filling, as the result the magnetic field leads to metal-insulator (or bad metal - insulator) phase transition. A model of the topological Kondo lattice defined on a honeycomb lattice is studied for the case when spinless fermion bands are half filled. It is shown that the hybridization between local moments and itinerant fermions should be understood as the hybridization between corresponding Majorana fermions of the spin and charge sectors. The system is a topological insulator, single fermion and spin excitations at low energies are massive. We will show that a spin gap induces a gap in the charge channel, it leads to an appearance of a topological insulator state with chiral gapless edge modes and the Chern number one or two depending on the exchange integrals' values. The relevance of this to the traditional Kondo insulator state is discussed.