Physicists from Finland’s Jyväskylä University and Aalto University have successfully created a two-dimensional topological crystalline insulator, marking the first experimental realization of a quantum material that scientists have predicted for more than a decade. Until now, attempts to manufacture them have been hampered by difficulties in developing suitable materials.
This breakthrough was led by Associate Professor Kezilbiek Shawulienu in collaboration with Aalto University researchers including Professor Peter Liljeroth and Professor Jose Lado. The researchers created the material by growing atomically thin films of just two layers of tin telluride (SnTe) on a niobium diselenide (NbSe2) substrate.
Atomicly thin crystal reveals unique quantum state
To characterize the material, the researchers used a combination of molecular beam epitaxy and cryogenic scanning tunneling microscopy, allowing them to study its electronic behavior with atomic-level precision.
Their measurements revealed pairs of conducting edge states that are characteristic of topological crystalline insulators. These special paths allow electrons to move along the edges of the material, protected by the symmetry of the crystal lattice.
Strain controls quantum properties of materials
Conducting edge states appear within large electronic bandgaps greater than 0.2 electron volts (eV). The researchers found that the tin telluride film was compressed by the underlying substrate, creating the strain necessary to stabilize the material’s topological state.
More importantly, the researchers demonstrated that these edge states can be tuned by varying the strain, providing a practical way to tune the electronic behavior of materials for future technologies.
Possibilities of future quantum electronics
First-principles quantum mechanical calculations confirmed that the observed edge states have a topological origin. The researchers also investigated how adjacent edge states interact and found that a combination of electrostatic interactions and quantum tunneling lead to changes in energy levels.
Because this material has a relatively large bandgap, its topological properties are expected to remain stable even at room temperature. Therefore, it represents a promising platform for exploring strain-tunable two-dimensional topological states, which could support future advances in spin-based electronics and nanoscale devices.
The research results were published in a magazine nature communications.
