A New Quantum State of Matter Unearthed

Research on topological states to advance quantum computing — a method that harnesses the power of atoms and molecules for computational tasks — has revealed a surprising new topological semi-metal that could change the face of technology.

W. Vincent Liu, associate professor of physics in the University of Pittsburgh’s Department of Physics and Astronomy, in collaboration with researchers at the University of Maryland and the University of Hamburg in Germany, are studying orbital degrees of freedom and nano-Kelvin cold atoms in optical lattices to better understand new quantum states of matter.

“We were surprised to find that such a simple system could reveal itself as a new type of topological state — an insulator that shares the same properties as a quantum Hall state in solid materials,” Liu said.

The quantum Hall effect, discovered in 1985, proved that when a magnetic field is applied perpendicular to the direction in which a current is flowing through a metal, a voltage is developed in the third perpendicular direction. Liu's work has yielded similar yet remarkably different results.

“This new quantum state is very reminiscent of quantum Hall edge states,” Liu said. “It shares the same surface appearance, but the mechanism is entirely different: This Hall-like state is driven by interaction, not by an applied magnetic field.”

The researchers developed an experimental design of optical lattices and tested the topological semi-metal state by loading very cold atoms onto the lattice, which formed global rotations, breaking time-reversal symmetry.

“By studying these orbital degrees of freedom, we were able to discover liquid matter that had no origins within solid-state electronic materials,” Liu said, adding that this liquid matter could lead to topological quantum computers and new quantum devices for topological quantum telecommunications.

The research is published in Nature Physics.

For more information, visit: www.pitt.edu