The best topological conductor yet: Spiraling crystal is the key to exotic discovery

The realization of so-called topological materials—which exhibit exotic, defect-resistant properties and are expected to have applications in electronics, optics, quantum computing, and other fields—has opened up a new realm in materials discovery.

Several of the hotly studied topological materials to date are known as topological insulators. Their surfaces are expected to conduct electricity with very little resistance, somewhat akin to superconductors but without the need for incredibly chilly temperatures, while their interiors—the so-called "bulk" of the material—do not conduct current.

Now, a team of researchers working at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has discovered the strongest topological conductor yet, in the form of thin crystal samples that have a spiral-staircase structure. The team's study of crystals, dubbed topological chiral crystals, is reported in the March 20 edition of the journal Nature.

The DNA-like spiraling structure, or helicoid, in the crystal sample that was the focus of thelateststudy exhibits a chirality or "handedness—as a person can be either left-handed or right-handed, and the left hand is a mirror image of the right hand. Chiral properties in some cases can be flipped, like a left-handed person becoming a right-handed person.

"In this new work we are essentially proving that this is a new state of quantum matter, which is also exhibiting nearly ideal topological surface properties that emerge as a consequence of the chirality of crystal structure," said M. Zahid Hasan, a topological materials pioneer who led the materials theory and experiments as a visiting faculty scientist in the Materials Sciences Division at Berkeley Lab. Hasan is also the Eugene Higgins Professor of Physics at Princeton University.