Robust Hot Electron and Multiple Topological Insulator States in PtBi₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Topological insulators possess unique boundary states protected by non-trivial bulk topology.
• Existing topological insulators typically have a single bulk gap protecting boundary states.

Purpose of the Study:

• To identify and characterize a novel quantum phase of matter beyond conventional topological insulators.
• To demonstrate the existence of multiple topological insulators and their unique properties.
• To explore the potential applications of these novel materials.

Main Methods:

• Theoretical prediction and characterization of multiple topological insulators.
• Experimental synthesis of a van der Waals material, PtBi2.
• Scanning tunneling spectroscopy (STS) to visualize boundary states.
• Testing the robustness of boundary states against environmental and geometric variations.

Main Results:

• Identification of a new quantum phase: multiple topological insulators with a ladder of topological gaps.
• Experimental verification of monolayer PtBi2 as a two-dimensional multiple topological insulator.
• Direct visualization of one-dimensional "hot electron" channels with nanometer-scale confinement.
• Demonstration of the topological protection and robustness of these channels.

Conclusions:

• Multiple topological insulators represent a new class of quantum matter with unique topological properties.
• PtBi2 is a promising material for realizing 2D multiple topological insulator states.
• The discovered topological hot electron channels offer potential for future applications, such as in photocatalysis.