Scientists at Ames Laboratory applied a terahertz electric field to drive periodic lattice oscillations in a model topological insulator. These additional fluctuations actually enhanced protected topological states. Image: US Department of Energy, Ames Laboratory.
Scientists at Ames Laboratory applied a terahertz electric field to drive periodic lattice oscillations in a model topological insulator. These additional fluctuations actually enhanced protected topological states. Image: US Department of Energy, Ames Laboratory.

Scientists at the US Department of Energy's Ames Laboratory have discovered that applying vibrational motion in a periodic manner to topological materials may be key to preventing dissipations of the desired electron states that would make advanced quantum computing and spintronics possible. They report their findings in a paper in npj Quantum Materials.

Some topological materials are insulators in their bulk form, but possess electron-conducting behavior on their surfaces. While the differences in the behavior of these surface electrons is what makes topological materials so promising for technological applications, it also presents a challenge. This is because uncontrolled interactions between surface electrons and the bulk material states can cause electrons to scatter out of order, leading to so-called ‘topological breakdown’. They are not protected by any ‘spontaneous symmetry’.

"Topological insulators that can sustain a persistent spin-locked current on their surfaces which does not decay are termed ‘symmetry protected’, and that state is compelling for multiple revolutionary device concepts in quantum computing and spintronics," explained Jigang Wang, a physicist at Ames Laboratory and Iowa State University. "But the topological breakdown due to surface-bulk coupling is a long-standing scientific and engineering problem."

To overcome this problem, Wang and his fellow researchers took a paradoxical approach called dynamic stabilization. This involved applying a terahertz electric field to drive periodic atomic vibrations, i.e. vibrational coherence, in the model topological insulator bismuth selenium (Bi2Se3). These extra ‘fluctuations’ actually enhanced the protected topological states, making the electronic excitations longer lived.

An analogy of such dynamic stabilization is the periodically driven Kapitza pendulum, named after Nobel Laureate Peter Kapitza, where an inverted, yet stable orientation is achieved by imposing a sufficiently high-frequency vibration of the pivot point. In a similar manner, additional dynamic stabilization can be achieved by driving quantum periodic motions of the lattice.

"We demonstrate the dynamic stabilization in topological matter as a new universal tuning knob, that can be used to reinforce protected quantum transport," said Wang. He believes this discovery has far-reaching consequences for the use of topological materials in many scientific and technological disciplines, such as disorder-tolerant quantum information and communications applications and spin-based, lightwave quantum electronics.

This story is adapted from material from Ames Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.