Physicists from the Universities of Jyväskylä and Aalto in Finland have created a two-dimensional topological crystalline insulator — a material that scientists have dreamed of for more than ten years. They grew an atomically thin film of two layers of tin telluride (SnTe) on a substrate of niobium diselenide (NbSe₂). This is the first experimental realization of the predicted structure, and it opens the way to quantum devices that operate at room temperature.
The key to success is the strain that arises from the film being compressed by the substrate. It is this strain that stabilizes the topological state. Pairs of conducting edge states, protected by the symmetry of the crystal lattice, appear in the material. Electrons move along the edges without loss, while a large band gap wider than 0,2 electron-volts remains inside.
The researchers used molecular beam epitaxy and low-temperature scanning tunneling microscopy to see these states with atomic precision. Quantum-mechanical calculations confirmed their topological origin. Moreover, the edge states can be tuned by changing the deformation — this provides a practical way to control electronic properties.
The large width of the band gap gives hope that the topological properties will persist even at room temperature. The material could become a platform for spintronics and the nanodevices of the future, where quantum effects work without cryogenic cooling.
Neighboring edge states interact through electrostatic forces and quantum tunneling, which the researchers also managed to study. The team, led by Associate Professor Kezilbejek Shavulienu in collaboration with Professors Peter Liljeroth and Jose Lado, published the results in Nature Communications.
Now physicists have a real sample that can be deformed and tuned — a step toward quantum electronics that will one day find its way into our gadgets.
