Physicists Spawn Rings of Exceptional Points Out of Dirac Cones

A schematic drawing of how a ring of exceptional points (shown in dashes) can be spawned from a Dirac point (a dot), and thus change the dispersion from a conical shape that is widely known into an exotic lantern-like shape. Credit: Yale University

Physicists outline a new concept called the “exceptional ring.”

Optics research just got a bit more exceptional, and the world may benefit.

Physicists have long known about the existence of isolated “exceptional points” — unique points where two physical states coalesce into one. Exceptional points give rise to counterintuitive phenomena; a more opaque material can seem more transparent, and light may be allowed to propagate in one direction but not the other.

Now, in a paper published in the journal Nature, scientists have outlined a new concept called the “exceptional ring.”

An exceptional ring is a continuous ring of exceptional points, and its discovery opens new avenues of research for basic science and technology, note the researchers. In this case, the exceptional rings were found in a slab of nanostructured material called a photonic crystal. The researchers found that exceptional rings arise from Dirac cones, which commonly occur in a 2D material and have been the focus of many important physics discoveries in the past decade.

“This finding may enable a number of exciting applications,” said co-lead author Chia Wei Hsu, a Yale postdoctoral researcher in applied physics. “Examples include more sensitive biological and chemical sensors, lasers with higher output power, and light-emitting devices with directional emission.”

Reference: “Spawning rings of exceptional points out of Dirac cones” by Bo Zhen, Chia Wei Hsu, Yuichi Igarashi, Ling Lu, Ido Kaminer, Adi Pick, Song-Liang Chua, John D. Joannopoulos and Marin Soljačić, 9 September 2015, Nature.
DOI: 10.1038/nature14889

The other co-lead authors of the research are Bo Zhen of MIT and Yuichi Igarashi of Smart Energy Research Laboratories, in Japan.