Cavity-enhanced superconducting response in an underdoped cuprate
Angela Montanaro, Vadim Plastovets, Nitesh Khatiwada, Jacopo Fiore, Giacomo Jarc, Abdullah Alabbadi, Antonio Mastropasqua, Enrico Maria Rigoni
Abstract
Superconductors carry electrical current without resistance when paired electrons condense into a coherent macroscopic quantum state. In underdoped cuprates, evidence suggests that pairing-related correlations and superconducting fluctuations can survive above the temperature at which global coherence is lost, pointing to phase fluctuations as a key limitation on superconductivity in this regime. Motivated by recent demonstrations of cavity-modified collective states in quantum materials, we investigate whether superconducting coherence can be stabilized by engineering the electromagnetic environment of the superconductor. We study an underdoped YBaCuO thin film in a tunable terahertz cavity formed with a semi-transparent gold mirror. From temperature-dependent terahertz transmission measurements, we find that the cavity enhances the superconducting response below the critical temperature, with an increase of the inferred superfluid weight. The effect becomes more pronounced at smaller cavity lengths and is accompanied by an upward shift of the superconducting onset temperature. Calculations based on a cavity-coupled model for phase-fluctuating superconductors capture these trends and support an interpretation in terms of cavity-enhanced phase stiffness. These results showcase the potential of cavity engineering for designing emergent functionalities in correlated systems.
AI Impact Assessments
(1 models)Scientific Impact Assessment
1. Core Contribution
This paper presents experimental evidence that embedding an underdoped YBa₂Cu₃O₇₋δ (YBCO) thin film inside a tunable terahertz Fabry-Pérot cavity can *enhance* the superconducting response — specifically increasing the inferred superfluid weight and producing a small upward shift (~1 K) in the superconducting onset temperature. This is a conceptually important result because prior experiments on cavity-coupled superconductors (organic superconductors, NbN) had observed only *suppression* of the superfluid density. The authors propose that in underdoped cuprates, where phase fluctuations rather than pairing strength limit superconductivity, the cavity acts through a different channel: it modifies the electromagnetic environment to stiffen the superconducting phase, rather than dressing pairing interactions. A theoretical model based on cavity-coupled XY/BKT physics supports this interpretation, predicting that cavity confinement gaps out low-energy photonic modes, thereby reducing their hybridization with phase fluctuations and increasing the effective phase stiffness.
2. Methodological Rigor
The experimental methodology is thorough and carefully constructed. The authors employ THz time-domain spectroscopy through a custom-built tunable cryogenic cavity, with nanometric control of mirror-sample separation. Several strengths stand out:
However, some limitations temper the rigor:
3. Potential Impact
This work has potentially transformative implications across several domains:
The practical impact is currently limited by the small magnitude of the effect and the requirement for macroscopic cavity assemblies, but the authors suggest that deposited cavity heterostructures and more anisotropic cuprates (e.g., Bi₂Sr₂CaCu₂O₈₊δ) could amplify the effect significantly.
4. Timeliness & Relevance
This paper arrives at a moment of intense activity in cavity quantum materials, following the recent Nature publications on cavity-altered superconductivity (Keren et al., 2026) and cavity-modified quantum Hall effects (Enkner et al., 2025). It directly addresses the open question raised by those works: can cavities enhance rather than suppress superconductivity? The choice of underdoped cuprates, where phase fluctuations are the limiting factor, is theoretically well-motivated and experimentally strategic. The paper also connects to the broader emerging field of fluctuation engineering in cavity QED settings.
5. Strengths & Limitations
Key Strengths:
Notable Limitations:
Overall Assessment
This is a high-impact experimental result that, if confirmed, represents a significant conceptual advance in cavity quantum materials — demonstrating that electromagnetic environment engineering can enhance rather than merely perturb superconductivity. The experimental execution is careful and the theoretical framework is physically reasonable, though the small effect size and phenomenological nature of the theory leave room for alternative interpretations. The work will likely stimulate substantial follow-up activity in both experiment and theory.
Generated Jun 17, 2026
Comparison History (21)
Paper 2 demonstrates a fundamentally new approach—using cavity engineering to enhance superconducting properties in cuprates, including increased superfluid weight and elevated onset temperature. This represents a novel intersection of cavity QED and condensed matter physics with broad implications for manipulating quantum materials. While Paper 1 provides important microscopic observations of channelised supercurrents in kagome superconductors, Paper 2 opens an entirely new paradigm for controlling superconductivity through electromagnetic environment engineering, with potentially transformative applications across correlated electron systems.
Paper 2 investigates underdoped cuprates (YBCO), a class of high-temperature superconductors. Demonstrating cavity-enhanced phase stiffness and an upward shift in the onset temperature in cuprates addresses a major grand challenge in condensed matter physics. While Paper 1 provides an excellent quantitative demonstration in a 2D material, modifying high-Tc superconductors holds vastly greater potential for revolutionary real-world energy applications. By mitigating phase fluctuations in correlated systems, Paper 2 paves a promising pathway toward stabilizing macroscopic quantum coherence at even higher temperatures.
Paper 1 likely has higher impact: it introduces a timely, broadly relevant mechanism—cavity (electromagnetic-environment) engineering—to enhance superconducting phase stiffness in underdoped cuprates, supported by tunable-cavity experiments plus a phase-fluctuation model. This connects quantum optics with strongly correlated superconductivity and could generalize across materials and devices. Paper 2 reports intriguing inverse/reentrant superconductivity in Eu-doped infinite-layer nickelates, but the phenomena occur at very low temperatures with a complex, more speculative interpretation, potentially limiting near-term applications and requiring stronger corroboration.
Paper 1 presents an experimental demonstration of cavity-enhanced superconductivity in a cuprate, bridging cavity quantum electrodynamics and strongly correlated materials. Modifying superconducting properties via the vacuum electromagnetic environment is a highly sought-after, groundbreaking capability with profound implications for high-Tc superconductivity and quantum material design. While Paper 2 offers interesting theoretical insights, Paper 1's experimental realization of cavity-stabilized coherence addresses a major challenge in the field, offering broader experimental and technological impact.
Paper 1 has higher impact potential because it demonstrates an active, tunable route—cavity engineering—to modify superconducting phase stiffness and onset temperature, offering a broadly applicable paradigm for controlling emergent order in correlated materials. The combination of experiment (THz cavity transmission) plus a supporting cavity-coupled phase-fluctuation model strengthens methodological rigor and causal interpretation. Its implications extend beyond a single compound class (potentially relevant to many fluctuating-order systems), and it is timely given rapid growth in polariton/cavity-modified quantum materials. Paper 2 is valuable but more materials-specific and largely observational (ARPES mapping).
Paper 2 demonstrates a novel method to enhance superconducting coherence and onset temperature in high-Tc cuprates using cavity electrodynamics. This cross-disciplinary approach addresses a major challenge in physics and offers a highly tunable pathway to manipulate macroscopic quantum states, giving it broader applicability and higher potential impact than the specific mechanism of surface superconductivity in Weyl semimetals described in Paper 1.
Paper 2 demonstrates a fundamentally new approach—using terahertz cavities to enhance superconductivity in cuprates—representing a novel intersection of cavity QED and condensed matter physics. It introduces a broadly applicable paradigm (cavity engineering of correlated states) with experimental validation, potentially impacting superconductivity research, quantum materials, and cavity QED communities. Paper 1, while valuable for nickelate superconductivity, is more incremental, focusing on strain effects in a specific material system with primarily theoretical predictions. Paper 2's broader conceptual innovation and cross-disciplinary relevance give it higher impact potential.
Paper 1 demonstrates a fundamentally novel concept—using cavity engineering to enhance superconducting coherence in cuprates, including raising the onset temperature. This opens a new paradigm for manipulating macroscopic quantum states via electromagnetic environment control, with broad implications for quantum materials, cavity QED, and potentially high-temperature superconductivity. Paper 2, while technically solid, provides incremental characterization of a specific superconductor's Fermi surface using established techniques. Paper 1's novelty, cross-disciplinary relevance, and transformative potential for designing emergent functionalities give it significantly higher impact.
Paper 1 addresses arguably the most important open problem in condensed matter physics—the microscopic mechanism of high-temperature superconductivity—and provides ab initio evidence for a non-BCS pairing mechanism in the material holding the ambient-pressure Tc record. The identification of 'attraction from reduced repulsion' as the pairing mechanism, validated against experimental pressure-dependent Tc data, represents a potentially transformative theoretical advance with implications for materials design. Paper 2, while innovative in applying cavity QED to modify superconducting properties, demonstrates a more incremental effect (enhanced superfluid weight) with narrower scope. Paper 1's breadth of impact across theory, computation, and materials design gives it higher potential impact.
Paper 2 likely has higher scientific impact: it provides experimental evidence that tailoring the electromagnetic environment (terahertz cavity) can enhance superconducting coherence and shift onset temperature in an underdoped cuprate, addressing a central, timely problem in correlated-electron physics and cavity–quantum-materials engineering. The approach is broadly relevant across superconductivity, quantum electrodynamics in solids, and materials design, and appears methodologically rigorous (temperature-dependent THz transmission plus modeling). Paper 1 is innovative with clear applications, but is primarily a proposal/prediction for SNSPD performance gains and may have narrower near-term cross-field impact without experimental validation.