Scientists observe exotic superradiant quantum phase once thought impossible

Amazing stuff!

"A team ... researchers reported the first direct observation of a surprising quantum phenomenon predicted over half a century ago, opening pathways for revolutionary applications in quantum computing, communication, and sensing.

Known as a superradiant phase transition (SRPT), the phenomenon occurs when two groups of quantum particles begin to fluctuate in a coordinated, collective way without any external trigger, forming a new state of matter.

The discovery was made in a crystal composed of erbium, iron, and oxygen that was cooled to minus 457 Fahrenheit and exposed to a powerful magnetic field of up to 7 tesla (over 100,000 times stronger than Earth's magnetic field) ..."

From the abstract:

"Two-level atoms ultrastrongly coupled with single-mode cavity photons are predicted to exhibit a quantum phase transition, entering a phase in which both the atomic polarization and the photonic field are finite even without external driving.

However, this phenomenon, the superradiant phase transition (SRPT), is forbidden by a no-go theorem due to the existence of the diamagnetic term.

Here, we present spectroscopic evidence for a magnonic SRPT in ErFeO3, where the role of the photonic mode (two-level atoms) in the photonic SRPT is played by an Fe3+ magnon mode (Er3+ spins). 

The absence of the diamagnetic term in the Fe3+-Er3+ exchange coupling ensures that the no-go theorem does not apply.

Ultrabroadband terahertz and gigahertz magnetospectroscopy experiments revealed the signatures of the SRPT in thermal equilibrium, a kink and a softening, respectively, of two spin-magnon hybridized modes at the critical point.

Systems near this phase are expected to harbor large-scale squeezing, which will potentially provide a route to next-generation quantum technologies."

Scientists observe exotic quantum phase once thought impossible

Scientists observe exotic quantum phase once thought impossible (original news release) "Discovery in a magnetic crystal could enable breakthroughs in quantum tech"

Observation of the magnonic Dicke superradiant phase transition (open access)

Fig. 1. Comparison between a light-matter system and a magnon-spin system for the Dicke SRPT.

Fig. 2. Spectroscopic evidence for the magnonic SRPT in ErFeO3.