Structural-Disorder-Induced Second-Order Topological Insulators in Three Dimensions

Area of Science:

• Condensed Matter Physics
• Materials Science
• Topological Matter

Background:

• Higher-order topological insulators (HOTIs) are typically protected by crystalline symmetries.
• Second-order topological insulators (SOTIs) in 3D exhibit chiral hinge modes.
• The existence of HOTIs in disordered, amorphous systems remains unexplored.

Purpose of the Study:

• To investigate the possibility of SOTIs in amorphous systems without crystalline symmetry.
• To explore the role of structural disorder in inducing topological phases.
• To demonstrate SOTIs in amorphous systems with time-reversal symmetry.

Main Methods:

• Theoretical prediction of topological phases in amorphous solids.
• Analysis of winding numbers related to quadrupole moments.
• Investigation of quantized longitudinal conductance and hinge states.

Main Results:

• Prediction of a novel SOTI phase in amorphous systems lacking crystalline symmetry.
• Observation of topological signatures including winding number, quantized conductance, and hinge states.
• Demonstration that structural disorder can induce SOTIs from trivial phases.

Conclusions:

• SOTIs can exist in amorphous materials without crystalline symmetry.
• Structural disorder can be beneficial, inducing topological phases.
• Amorphous SOTIs are achievable even with time-reversal symmetry.