Superradiance Impacts Fermionic Pairing & System Behavior

Researchers led by Yilun Xu at Peking University have uncovered a new way to understand how different phase transition influence one another in complex systems. Traditionally, studying the interaction between multiple order parameter has been challenging. However, their work shows that a phase transition in one order parameter can directly affect the strength of another, revealing a universal critical scaling law that quantifies this relationship.

By analysing systems with two interacting order parameters, the team demonstrated that superradiance  can both enhance and suppress fermionic pairing—a key mechanism behind Superconductivity—particularly near the critical temperature T=TcT = T_cT=Tc​. This discovery establishes a fundamental connection between different types of phase transitions, offering new insights into the behaviour of complex quantum systems.

A change in one phase transition can directly alter the behaviour of another, establishing a predictable relationship between them. Specifically, the analysis of systems governed by multiple factors showed how superradiance, a form of enhanced light emission, can both strengthen and weaken fermionic pairing, a process vital to superconductivity. Researchers have demonstrated a direct link between phase transitions in complex systems, revealing how a change in one can influence the strength of another.

These systems, unlike those governed by a single factor, exhibit richer and more intricate behaviour; imagine the order parameters as dials on a complex machine, each controlling a different aspect of its operation. The team focused on systems described by two such parameters, showing how superradiance, a collective glow emitted by a group of atoms, similar to a choir amplifying a single voice, can both enhance and suppress fermionic pairing, a key process in superconductivity. This interplay is governed by principles outlined in Landau’s theory, a set of rules describing how materials change state, like water freezing into ice.

Quantifying Interdependent Phase Transitions Reveals Accelerated Critical Scaling

Systems governed by two order parameters now exhibit critical scaling rates 3.7 times faster than those with a single parameter, unlocking analysis previously limited by the inability to predict interaction between phase transitions. This allows physicists to quantify how a transition in one property directly influences another, a phenomenon that remained largely uncharacterised until now. Dr. Peter Kirwan and Dr. Andrew Daley established a universal critical scaling rate, enabling evaluation of the relationship between order parameters and prediction of physical effect manipulation, verified using the two-mode Rabi and 1D Fermi Dicke models.

Observations in the two-mode Rabi and 1D Fermi Dicke models demonstrate that transitions in one physical property directly impact another. In the Rabi model, the superradiant phase transition, a collective emission of photons, manipulated the strength of two-spin pairing. The 1D Fermi Dicke model showed the same transition suppressing the superconducting band gap, a vital element in materials exhibiting superconductivity. This manipulation offers a potential route to tailoring material properties without discovering entirely new superconducting compounds, although translating these principles into complex, real-world materials remains a strong challenge.

Quantifying Interparameter Relationships via Critical Scaling Rates

Landau’s theory underpinned the technique for dissecting these complex systems, acting as a framework akin to establishing rules for how materials change state, such as water freezing or boiling. The team focused on systems governed by two ‘order parameters’, measurable physical quantities defining a material’s state, including magnetism or conductivity. Researchers developed a method to calculate a ‘critical scaling rate’, quantifying how a shift in one order parameter directly impacted the strength of the other, allowing prediction of the interaction between them.

Quantifying order parameter interplay via critical scaling in simplified systems

Predicting how multiple properties within a material interact is important for designing new technologies, but this relationship has remained a significant hurdle. The team relied on specific, simplified models, the two-mode Rabi and 1D Fermi Dicke systems, and acknowledge that determining the broad applicability of their derived rate to more complex physical systems is an open question. Even within these controlled environments, however, a key framework for investigating more complex materials is established.

Measurable physical quantities, such as magnetism or conductivity, define a material’s state and were the focus of this investigation. The team’s quantified critical scaling rate offers a new approach to predict how changes in one property will affect another, potentially guiding the design of materials with tailored characteristics. A predictable relationship between multiple, simultaneously changing material properties represents a major advance in condensed matter physics. A transition in one order parameter directly influences the strength of another, revealing a previously unquantified interaction. Applying the framework describing how materials change state, the team developed a method to evaluate this connection and verified it using models of light-matter interaction.

The researchers demonstrated that a change in one measurable property of a material directly influences another, revealing a predictable relationship between simultaneously changing characteristics. This finding is important because understanding how multiple properties interact is crucial for materials design. Using Landau’s theory of continuous phase transitions, they quantified this interplay with a ‘critical scaling rate’ in simplified models, including the two-mode Rabi and 1D Fermi Dicke systems. The authors suggest this work establishes a new approach for studying complex systems with multiple defining properties.