Majorana modes in a topological insulator/s-wave superconductor heterostructure

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Topological Matter

Background:

• Experimental signatures of Majorana fermions (MFs) have been observed.
• These signatures were found in heterostructures of topological insulators (TI) on s-wave superconductors.
• The precise nature and stability of these MFs require further theoretical investigation.

Purpose of the Study:

• To provide strong theoretical support for recent experimental findings of MFs.
• To investigate the behavior and stability of MFs in TI-superconductor heterostructures.
• To elucidate the role of impurities on MF properties.

Main Methods:

• Analytical calculations to demonstrate MF mode emergence.
• Numerical simulations to analyze the local density of states (LDOS).
• Theoretical modeling of impurity effects on MF stability.

Main Results:

• MF modes are predicted on both top and bottom TI layers, well-separated for n ~ 6.
• The top MF mode extends with increasing layer number (n), aligning with experimental data.
• A low-energy bound state accompanies the MF at the vortex core, creating distinct peaks in LDOS.
• Local impurities can remove the side peak, leading to a symmetric LDOS and preserving the zero-energy MF.
• MF stability is compromised by moderate concentrations of impurities.

Conclusions:

• The theoretical framework strongly supports the experimental observation of MFs.
• MFs exhibit unique properties at the vortex core, including an accompanying bound state.
• While robust against single impurities, MFs show reduced stability with increased impurity concentration.