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Did You Know? Department of Physics and Astronomy home to several scientists exploring Nobel Prize-related research

Earlier this week, three researchers from the University of Washington, Princeton University and Brown University were named 2016 Nobel Prize in Physics recipients, for revealing what the organization called “secrets of exotic matter.” The trio of scientists—- David Thouless, F. Duncan M. Haldane and J. Michael Kosterlitz—- have used mathematical methods to study unusual phases, or states, of matter, such as superconductors, superfluids or thin magnetic films. They were recognized for their contributions to topology, a branch of mathematics that describes properties that only change step-wise. The exotic materials the Nobel Laureates examined manifest novel quantum properties that may improve future electronics, superconductors and lead to quantum computers.

But did you know that WVU is home to a number of experts in topology, materials science and condensed matter physics?

• Lian Li, Carroll Chair of Physics, explores the growth and microscopy of the electronic properties of topological matter, including insulators and superconductors. Lian recently joined the WVU from the University of Wisconsin-Milwaukee, bringing unique capabilities with him.

• Tudor Stanescu, associate professor, has spent the last decade modeling the interfaces of topological insulator in proximity to other materials, such as superconductors. He contributes to the global hunt for Majorana Fermions – particles that are their own anti-particle.

• Aldo Romero, associate professor, uses first principles computer simulations to model topological matter and predicting new quantum phases of matter.

• Professors Mikel (Micky) Holcomb (assistant) and Alan Bristow (associate) use optical methods to isolate and control the surfaces. Optical methods may present a way to overcome the challenges in determining the conduction properties.

• Assistant Professor Cheng Cen explores exotic materials that contain very heavy atoms that bind the electrons strongly, confining them and changing the conduction properties. Her work is funded by prestigious early career awards from National Science Foundation and U.S. Department of Energy.

• In direct connection to this year’s Nobel Prize, Professor Leonardo Golubovic was named as fellow of the American Physical Society for his theory relating the Kosterlitz-Thouless transition to interfaces of biological membranes.

• Associate Vice President of Research Sheena Murphy, who also recently joined WVU’s faculty from the University of Oklahoma, has previously worked with both superfluid helium and conducting variants of the phases central to the Nobel prize.

In the early 1970s, two of the Nobel Laureates – Kosterlitz and David Thouless—- overturned the then-theory that superconductivity or superfluidity could not occur in thin layers. They demonstrated that superconductivity could occur at low temperatures and also explained the mechanism, phase transition that makes superconductivity disappear at higher temperatures. This work was the first prediction of exotic matter. 

Exotic matter occurs at low temperatures or in very thin films or wires, when normal materials transition into phases where quantum effects are more evident. Cooling overcomes the random jostling of electrons that reduces electrical conductivity and creates a new phase, namely a superconductor. Conductivity in solids is a result of the motion, or momentum, of electrons inside the host crystal. Most properties of normal conductors arise from the bonding of constituent atoms and their positions in the crystal, which limits the range of momentum for conducting electrons. Conduction properties of exotic matter are defined by the paths electrons take inside the solid.

Thouless found that this is defined by the topological order, which comes from geometry and effectively counts the number of breaks in the electron path through the possible range of momentum. Conceptually, these breaks are often related to holes in donuts and coffee mug handles, as compared to the lack of holes in a bread roll or a wine glass; see Figure 1.

The point being that the surface of a donut and a coffee cup can be morphed from one to another, without changing the number of holes or the topological order. However, a wine glass cannot be morphed into a coffee mug without adding a hole, which changes the topological order and the conduction properties.

The condensed matter physics group out to dinner with President Gee. From left to right Leonardo Golubovic, Wathiq Abdul-Razzaq, Tudor Stanescu, Edward Flagg, Mohindar Seehra, Aldo Romero, Cheng Cen, Gordon Gee, Alan D. Bristow, James P. Lewis and Mikel Holcomb. Missing from the photo are newcomers Matthew Johnson, Lian Li, and Sheena Murphy.

One of the more recent examples of topological material is the so called topological insulator, which is insulating throughout the material but has highly conducting surfaces. The topological order preserves the conductivity regardless of the roughness of the surface, that would normally destroy normal conductors. It is this robust surface conduction that is of value for applications such as quantum computing. Similar arguments can be made for confinement at the quantum scale.

The condensed matter physics group at WVU works to provide a better understanding of materials, their interfaces and interactions, and to lay the foundation for applications based on the discovery of new physics. Their work is supported by federal funding and in part by the WV Higher Education Policy Commission’s Research Challenge Grant Program. The program primarily supports student researcher activity in low-dimensional and interface physics for rational design of future electronic materials.

For more information, visit https://www.nobelprize.org/nobel_prizes/physics/laureates/2016/press.html.

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