Observation of the magnonic Dicke superradiant phase transition.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40184449.
- Also identified by DOI 10.1126/sciadv.adt1691 and PMC identifier 13155478.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
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 ErFeO<sub>3</sub>, where the role of the photonic mode (two-level atoms) in the photonic SRPT is played by an Fe<sup>3+</sup> magnon mode (Er<sup>3+</sup> spins). The absence of the diamagnetic term in the Fe<sup>3+</sup>-Er<sup>3+</sup> 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.