First Experimental Detection of Dirac Exceptional Points

Exceptional points (EPs) represent distinctive kinds of energy-level degeneracies that arise in non-Hermitian systems. Although they were initially suggested over a hundred years ago, scientists could only detect two forms of these exceptional points until recently. These observations revealed unusual states of matter within different substances such as Dirac and Weyl semimetals.

Expanding upon recent theoretical research, scientists from the University of Science and Technology of China aimed to empirically identify a novel category of exceptional points called Dirac exceptional points. Their study is outlined in this document. published in Physical Review Letters This could unlock new thrilling opportunities for exploring non-Hermitian dynamics and for devising methods to effectively manage quantum systems with precision.

"Our motivation came from a prior theoretical study Xing Rong, who co-authored the study, explained to The News Pulse about introducing a new kind of exceptional point called Dirac EPs. He noted that this particular form of exceptional point differs significantly from every single one documented through experiments in the last fifty years. Their objective was to turn their theoretical concept into an observable scientific phenomenon.

Dirac EPs represent theoretical intersections where Dirac points from Hermitian systems merge with exceptional points (EPs) found in non-Hermitian systems. In their latest research, Rong and his team aimed to create and detect these energy-level degeneracies using nitrogen-vacancy centers in diamond—a type of atomic-scale quantum system embedded in a solid-state structure.

We designed a non-Hermitian Hamiltonian featuring Dirac exceptional points by incorporating a spin-squared operator term. _z ² ) into a three-tiered non-Hermitian system," clarified Rong. "Utilizing our earlier devised dilation technique, we realized this Hamiltonian experimentally through nitrogen-vacancy centers within diamond. The presence of Dirac exceptional points was verified by detecting real eigenvalues close to the Dirac EP and state degeneracy precisely at the EP.

The team’s successful detection of Dirac exceptional points, facilitated by a Hermitian-like symmetry within non-Hermitian systems, might quickly spur fresh experimentation in this area. Such endeavors could enhance our comprehension of these novel instances of energy-level degeneracy, possibly guiding the creation of improved and dependable methods for managing quantum states.

Rong stated, "The Dirac EP displays a distinctive real-valued eigenvalue spectrum around it, which challenges the common belief that standard EPs usually come with complex eigenvalues. This feature allows for adiabatic evolution within non-Hermitian systems and helps mitigate dissipative impacts. Consequently, this holds substantial potential for use in topological physics associated with EPs as well as in quantum control procedures."

Rong and his team members anticipate that their research might ignite additional advancements within the realm of non-Hermitian and quantum physics. Going forward, their experimental detection of Dirac exceptional points may offer quantum researchers and developers a valuable pathway toward enhancing command over numerous leading-edge quantum innovations such as quantum sensors and computing systems.

By utilizing Dirac exceptional points (EPs), we can circumvent non-adiabatic transitions typically linked with these points, enabling the potential for experimental exploration into intricate geometric phases," noted Rong. "Consequently, the achievement of observing a Dirac EP in our research opens up avenues for experimenting with geometric phases within non-Hermitian systems.

More information: Yang Wu and colleagues observed Dirac exceptional points through experimental analysis. Physical Review Letters (2025). DOI: 10.1103/PhysRevLett.134.153601 . On arXiv : DOI: 10.48550/arxiv.2503.08436

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