Fractional charged edge states in ladder topological insulators

Area of Science:

• Condensed Matter Physics
• Topological Materials
• Quantum Mechanics

Background:

• Topological insulators exhibit unique electronic properties protected by symmetries.
• Spin-orbit couplings play a crucial role in realizing topological phases.
• Fractional charges in topological systems are of significant theoretical and experimental interest.

Purpose of the Study:

• To propose and analyze a two-leg ladder topological insulator model.
• To investigate the properties of fractional charged edge states.
• To explore the realization of this model using cold atoms in optical lattices.

Main Methods:

• Theoretical modeling of a two-leg ladder system with intra-chain and inter-chain spin-orbit couplings.
• Symmetry analysis (time-reversal and chiral symmetry) to determine topological class (CII).
• Investigation of edge state properties, including charge distribution and detectability via momentum density.

Main Results:

• The proposed model supports four fractional charged edge states in the chiral symplectic (CII) class.
• Edge states exhibit fourfold degeneracy due to time-reversal and chiral symmetry.
• Each of the two edge states at one end carries a half charge and is distinguishable by momentum density.
• Driving the system to the AIII class via a magnetic field reveals distinct topological phases with degenerate edge states.

Conclusions:

• The model provides a platform for studying fractional charges in topological insulators.
• The unique properties of the edge states offer potential for novel electronic devices.
• Experimental realization with cold atoms in optical lattices is feasible, enabling further investigation.