Physicists discover ring of exotic ‘exceptional points’

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)

Physicists have long known about the existence of unique points where two physical states coalesce into one. They call them “exceptional points.”

These 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.”

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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,” says co-lead author Chia Wei Hsu, a Yale University 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.”

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

Source: Yale University