A quantum material that existed only in theory for more than a decade has now been built in a lab in Finland. Physicists at the University of Jyväskylä and Aalto University grew an atomically thin crystal that conducts electricity only along its edges, a behavior that could eventually work at room temperature.
Two layers of tin telluride on a special base
Associate Professor Kezilbeiek Shawulienu led the team that made the material by stacking just two layers of tin telluride (SnTe) on top of a niobium diselenide (NbSe2) substrate. The researchers used molecular beam epitaxy to grow the film and then probed it with low temperature scanning tunneling microscopy. That let them see the material's electronic structure atom by atom. They found pairs of conducting edge states, the hallmark of a topological crystalline insulator. These states are protected by the symmetry of the crystal lattice, meaning electrons travel along the edges without scattering.
Strain as a control knob
The tin telluride film is compressed by the underlying substrate, creating strain that stabilizes the material's topological state. The team showed that changing the strain adjusts the edge states, giving researchers a practical way to tune the material's electronic behavior. The edge states appear within a large electronic band gap of more than 0.2 electron volts. First principles quantum mechanical calculations confirmed the states have a topological origin. The researchers also observed that neighboring edge states interact, shifting their energy levels through a mix of electrostatic forces and quantum tunneling.
A platform for room temperature quantum electronics
Because the band gap is relatively large, the material's 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. The work could support future advances in spin based electronics and nanoscale devices. The findings were published in the journal Nature Communications.
