Electron fractionalization in two-dimensional graphenelike structures

TL;DR

This paper demonstrates the existence of fractionally charged topological excitations in two-dimensional graphenelike structures that preserve time-reversal symmetry, expanding the understanding of fractionalization beyond quantum Hall systems.

Contribution

It introduces a new class of fractionalized excitations in graphenelike materials with time-reversal symmetry, linking topological zero-modes to Dirac fermion mass twists.

Findings

Fractionally charged topological excitations exist in graphenelike structures.

Zero-modes are analogous to fractional vortices in p-wave superconductors.

Topological excitations relate to phase twists in Dirac fermion masses.

Abstract

Electron fractionalization is intimately related to topology. In one-dimensional systems, fractionally charged states exist at domain walls between degenerate vacua. In two-dimensional systems, fractionalization exists in quantum Hall fluids, where time-reversal symmetry is broken by a large external magnetic field. Recently, there has been a tremendous effort in the search for examples of fractionalization in two-dimensional systems with time-reversal symmetry. In this letter, we show that fractionally charged topological excitations exist on graphenelike structures, where quasiparticles are described by two flavors of Dirac fermions and time-reversal symmetry is respected. The topological zero-modes are mathematically similar to fractional vortices in p-wave superconductors. They correspond to a twist in the phase in the mass of the Dirac fermions, akin to cosmic strings in particle physics.