Physicists from the University of Jyväskylä and Aalto University in Finland have successfully created a two dimensional topological crystalline insulator, marking the first experimental realization of a quantum material that scientists had predicted for more than a decade. Until now, attempts to produce it had been held back by difficulties in developing the right materials.
The breakthrough was led by Associate Professor Kezilbeiek Shawulienu in collaboration with Aalto University researchers, including Professor Peter Liljeroth and Professor Jose Lado. The team fabricated the material by growing an atomically thin film consisting of just two layers of tin telluride (SnTe) on top of a niobium diselenide (NbSe2) substrate.
Atomically Thin Crystal Reveals Unique Quantum States
To examine the material’s properties, the researchers used molecular beam epitaxy together with low temperature scanning tunneling microscopy, allowing them to probe its electronic behavior with atomic level precision.
Their measurements revealed pairs of conducting edge states, a defining feature of topological crystalline insulators. These special pathways allow electrons to travel along the edges of the material and are protected by the symmetry of the crystal lattice.
Strain Controls the Material’s Quantum Properties
The conducting edge states appear within a large electronic band gap of more than 0.2 electron volts (eV). The team found that the tin telluride film is compressed by the underlying substrate, creating strain that is essential for stabilizing the material’s topological state.
Even more importantly, the researchers demonstrated that these edge states can be adjusted by changing the strain, offering a practical way to tune the material’s electronic behavior for future technologies.
Potential for Future Quantum Electronics
First principles quantum mechanical calculations confirmed that the observed edge states have a topological origin. The team also examined how neighboring edge states interact, finding that their energy levels shift because of a combination of electrostatic interactions and quantum tunneling.
Because the material has a relatively large band gap, its topological properties are expected to remain stable even at room temperature. That makes it a promising platform for exploring strain tunable two dimensional topological states and could support future advances in spin based electronics and nanoscale devices.
The findings were published in the journal Nature Communications.