Photo credit: phys.org

Breakthrough Discovery of Superradiant Phase Transition at Rice University

A research team at Rice University has made an unprecedented discovery by observing a quantum phenomenon that was predicted over 50 years ago, potentially transforming fields such as quantum computing, communication, and sensing.

This phenomenon, termed a superradiant phase transition (SRPT), occurs when two groups of quantum particles begin to fluctuate in a coordinated manner without external influence, resulting in a new form of matter.

The researchers conducted their experiment on a crystal made up of erbium, iron, and oxygen, which was cooled to an astonishing minus 457 degrees Fahrenheit and subjected to a powerful magnetic field exceeding 7 tesla, a force over 100,000 times stronger than the Earth’s magnetic field. This groundbreaking work is detailed in a study recently published in Science Advances.

Dasom Kim, a doctoral student in Rice’s Applied Physics Graduate Program and the lead author of the study, explained that the SRPT was originally theorized to stem from the interactions between quantum vacuum fluctuations and matter fluctuations. “In our study, we observed this transition through the coupling of two distinct magnetic subsystems—the spin fluctuations of iron ions and erbium ions within the crystal,” Kim stated.

In this context, ‘spin’ refers to the magnetic orientation of electrons or particles, visualized as tiny arrows that are constantly rotating and pointing in specific directions. When these spins align, they create magnetic patterns that can ripple through the material, generating what is known as a magnon—a collective excitation across the material.

The prior theoretical debate surrounding the feasibility of observing an SRPT was due to a “no-go theorem” that applies to light-based systems. However, by achieving the transition in a magnetic crystal via the interactions of two spin subsystems, the researchers successfully circumvented this limitation, establishing a magnonic interpretation of the phenomenon.

In their experiments, the magnons produced by the iron ions served a role analogous to vacuum fluctuations, while the spin fluctuations of the erbium ions represented the matter fluctuations. The team employed sophisticated spectroscopic techniques to detect distinct indicators of an SRPT, noticing a disappearance in the energy signal of one spin mode along with a clear shift in another. These spectral signatures aligned perfectly with theoretical predictions for the transition into the superradiant phase, giving the researchers confidence in their findings.

“We have established an ultrastrong coupling between these two spin systems and successfully observed an SRPT, overcoming previously established experimental limitations,” Kim said.

The excitement among researchers stems not only from confirming a long-standing prediction in physics but also from the implications this discovery has for future quantum technologies. The collective quantum states formed during the SRPT exhibit properties that could significantly enhance the performance of quantum-based technologies.

“Near the quantum critical point of this transition, the system naturally stabilizes quantum-squeezed states, which drastically reduce quantum noise and enhance measurement precision,” Kim explained. “This could lead to revolutionary advances in quantum sensors and computing technologies, significantly improving their fidelity and sensitivity.”

Sohail Dasgupta, a fellow graduate student at Rice who modeled the theoretical aspects of the SRPT alongside Kaden Hazzard, an associate professor of physics and astronomy, noted the importance of incorporating the specific magnetic properties of the crystal into their models for accurate results. “When theoretical predictions match experimental data—a rare occurrence in scientific research—it is extremely gratifying,” Dasgupta remarked.

Hazzard further emphasized that this achievement illustrates how concepts from quantum optics can be applied within solid materials. “This discovery opens a fresh avenue for creating and controlling phases of matter by applying principles from cavity quantum electrodynamics,” he stated.

The crystal utilized in this study is a representative example of a broader category of materials, indicating that this research lays the groundwork for investigating quantum phenomena in other materials with similarly interacting magnetic features.

Junichiro Kono, a leading figure in the study and the Karl F. Hasselmann Professor of Engineering, remarked on the significance of demonstrating a form of SRPT driven solely by the coupling of two internal matter fluctuations. “This represents a notable breakthrough in quantum physics, establishing a newfound framework for comprehending and exploiting intrinsic quantum interactions within various materials,” Kono stated.

More information:

Dasom Kim et al, Observation of the magnonic Dicke superradiant phase transition, Science Advances (2025). DOI: 10.1126/sciadv.adt1691

Source
phys.org