The research focuses on lead halide perovskites, an emerging class of materials well-known for their remarkable optoelectronic properties and facile fabrication. These materials present a complex interplay between electronic excitations and the crystal lattice, serving as a fertile ground for exploring cooperative quantum dynamics in solid-state systems. Unlike conventional semiconductor structures, where electron–phonon interactions generally disrupt coherence, lead halide perovskites demonstrate a remarkable capacity to harness these interactions, promoting rather than inhibiting collective quantum behavior under the right conditions.

Central to this breakthrough is the identification of spontaneously synchronized polaronic lattice oscillations that accompany the collective electronic dipole emission during superfluorescence. Polaronic effects typically describe the coupling of charge carriers with lattice distortions; here, this coupling forms a coherent pattern of lattice deformations that act synergistically with the electronic excitations. This discovery overturns the conventional view that lattice motions merely serve as a decoherence channel, instead positioning them as active participants in establishing long-range quantum order. Such a phenomenon suggests the formation of a new hybrid state, where electronic and lattice degrees of freedom become intricately entangled.

To fully comprehend the mechanisms at work, the researchers developed an effective theoretical field model describing the exciton–lattice interactions within the perovskite crystal framework. This model reveals a critical polaron density threshold beyond which the system undergoes a phase transition into an electronically and structurally entangled solitonic state. Soliton-like excitations are known in nonlinear systems for their ability to maintain stable, localized wave packets over extended distances. Their emergence in this solid-state environment indicates that the material can sustain coherent wave-like electronic states that are stabilized by the lattice structure itself, even at temperatures where thermal agitation would typically obliterate such order.

The phase transition described is highly nontrivial and involves two simultaneous and cooperative processes. First, incoherent and disordered polaronic lattice deformations spontaneously organize into a quasi-ordered structure, breaking the symmetry of the lattice in a subtle yet crucial manner. Concurrently, a macroscopic quantum coherence develops among the exciton population, creating a collective dipole moment that radiates coherently as superfluorescence. This dual ordering process establishes a novel state of matter where the usual antagonism between electrons and phonons is transformed into a unifying foundation for emergent quantum phenomena.

Remarkably, the recombination of excitons within this entangled solitonic phase culminates in the emission of intense bursts of superfluorescence at temperatures significantly above room temperature. Superfluorescence, characterized by the spontaneous and cooperative emission of light from a large ensemble of coherently excited dipoles, has traditionally been confined to low-temperature regimes due to the need for prolonged coherent lifetimes. This demonstration in lead halide perovskites marks a significant leap forward, presenting a viable route to integrating macroscopic quantum emitters into devices operable under ambient conditions.

This study also brings to light fundamental connections between transient non-equilibrium phenomena induced by impulsive excitation and equilibrium-like phase transitions achievable via thermal control. It suggests that the transient superfluorescence process observed immediately following pulsed photoexcitation shares deep theoretical parallels with phase transitions known from condensed matter physics, such as symmetry breaking and order parameter emergence. This insight enriches our conceptual understanding of how externally driven quantum systems traverse complex energy landscapes towards coherent states.

From a materials science perspective, the research highlights the necessity of precisely tuning electron–lattice interactions to favor collective coherence. Lead halide perovskites offer a versatile platform where multiple modes of electron–phonon coupling coexist, ranging from relatively soft lattice vibrations to more pronounced polaronic effects. The identification of which specific lattice dynamics facilitate solitonic coherence versus those that hamper it is critical; by selectively engineering the lattice environment and electron interaction parameters, new classes of quantum materials may be designed to sustain high-temperature macroscopic quantum states.

This paradigm-shifting work underlines the importance of including lattice dynamics not merely as environmental noise but as integral components capable of stabilizing exotic quantum states in solids. Consequently, it paves the way for future exploration of hybrid quantum states that exploit collective lattice-electronic phenomena for robust quantum technologies, including ultrafast coherent light sources, quantum information platforms, and sensors with enhanced sensitivity that function without the burdensome need for cryogenic cooling.

Furthermore, the discovery invites a reevaluation of long-standing assumptions regarding decoherence mechanisms in solid-state quantum systems. While thermal fluctuations have historically been seen as the nemesis of quantum coherence, the present findings suggest scenarios where the environment can be co-opted to foster synchronization and coherence, reminiscent of self-organizing principles observed in complex biological and chemical systems.

In practical terms, this research could accelerate the deployment of quantum devices based on perovskite materials, whose ease of processing and tunable properties already make them attractive for photovoltaics and light-emitting diodes. Embedding coherent quantum functionalities in such material platforms may yield unforeseen synergies, merging classical and quantum regimes with wide-ranging technological impact.

The theoretical and experimental frameworks established here open numerous avenues for probing the nature of electron–phonon entanglement, collective excitations, and their dynamic evolution in nonequilibrium conditions. Subsequent investigations are poised to explore the scalability of these solitonic superfluorescent states, their coherence times under varying thermal backgrounds, and their response to controlled structural modifications.

Overall, this study marks a milestone in materials quantum science by demonstrating that intricate electron–lattice coupling can catalyze the spontaneous emergence of macroscopic quantum coherence, heretofore confined to ultracold environments, now attainable at technologically relevant temperatures. Its implications resonate across condensed matter physics, quantum optics, and materials engineering, heralding a new era in the design of quantum functional materials.

Subject of Research: High-temperature macroscopic quantum coherence and superfluorescence in lead halide perovskites through exciton–lattice interactions.

Article Title: Unconventional solitonic high-temperature superfluorescence from perovskites.

Article References:
Biliroglu, M., Türe, M., Ghita, A. et al. Unconventional solitonic high-temperature superfluorescence from perovskites. Nature (2025). https://doi.org/10.1038/s41586-025-09030-x

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Hydrogen sulfide, a simple molecule when composed as H₃S under high pressures, made headlines several years ago owing to its remarkable superconducting transition temperature (T_c) exceeding 200 K. This stunning discovery created a paradigm shift by illustrating that conventional electron-phonon mechanisms, long thought incapable of producing superconductivity at such formidable scales, might indeed underlie these unprecedented critical temperatures. However, despite theoretical predictions and indirect experimental indications, the direct spectroscopic characterization of the superconducting gap — a hallmark of the ordered state — remained elusive until now.

The superconductor’s energy gap, often dubbed the order parameter, embodies the energy scale at which electrons pair up to form Cooper pairs and condense into a superconducting phase. Detecting and measuring this gap with high precision stands as a cornerstone to confirming the nature of superconductivity, distinguishing between conventional phonon-mediated mechanisms and more exotic pairing scenarios such as those involving spin fluctuations or unconventional symmetries. In the case of hydrogen sulfide, tunneling spectroscopy, which probes electronic states near the Fermi level with exquisite energy resolution, has successfully captured this spectral fingerprint for the first time.

According to the recent report by Du, Drozdov, Minkov, and collaborators, tunneling measurements revealed a superconducting gap value of approximately 30 millielectronvolts (meV) for the H₃S sample designated as S1. This value, although substantial, intriguingly falls below the magnitude anticipated by current theoretical frameworks, which had predicted larger gap amplitudes based on strong electron-phonon coupling models. Additionally, the so-called 2Δ/k_BT_c ratio — a dimensionless parameter that scales the gap with respect to the critical temperature — was measured at 3.54, aligning closely with the classic Bardeen-Cooper-Schrieffer (BCS) theory expectation for weak to moderate coupling superconductors.

This apparent discrepancy between empirical data and theoretical predictions opens a compelling dialogue within the superconductivity community. While the isotope effect observed, involving substitution with deuterium to form D₃S, and the consistency with an s-wave symmetry gap strongly point towards phonon-driven pairing interactions, the reduced gap magnitude invites more nuanced scrutiny. This could suggest that current theoretical treatments, though sophisticated, might yet lack the full complexity of the actual interactions or structural inhomogeneities present in these pressurized samples.

Moreover, the investigations uncovered evidence of a multigap superconducting scenario within inhomogeneous hydrogen sulfide specimens. Multigap superconductivity, wherein distinct gaps coexist on different parts of the Fermi surface or in spatially segregated superconducting phases, represents a richer and more intricate state than single-gap models. Its presence here highlights the heterogeneous nature of high-pressure hydrides and the necessity for comprehensive studies addressing phase separation, crystal structure variations, and their influence on superconducting parameters.

The implications of these findings extend far beyond hydrogen sulfide alone. The successful application of tunneling spectroscopy to dissect the superconducting gap in such challenging experimental conditions underscores the technique’s potency as a diagnostic tool. It paves the way for analogous explorations across the broader family of metal superhydrides and related materials. Understanding their superconducting gap structures with high fidelity is vital for decoding the mechanisms responsible for their often remarkably high critical temperatures and for guiding the discovery of new compounds operable at lower pressures.

These developments dovetail with a wider scientific pursuit to link microscopic interactions with macroscopic superconducting properties. Resolving the nature of electron-phonon coupling strength, anisotropies in the order parameter, or the presence of competing phases can decisively inform the direction of theoretical modeling and synthetic efforts. Furthermore, such insight contributes to the ultimate goal of engineering materials capable of attaining room-temperature superconductivity under ambient or technologically feasible conditions.

The interplay between theory and experiment witnessed in this work exemplifies the dynamic evolution of superconductivity research. The direct experimental detection of a superconducting gap, particularly with high resolution and under multi-megabar pressures, sets a new benchmark. Yet it also raises new questions, such as the precise origin of the discrepancy between observed and predicted gap magnitudes and the full character of the multigap phenomena manifesting in these complex hydride systems.

Expanding the scope of this research to include systematic isotopic substitution and pressure-dependent studies could unravel further subtleties governing pairing interactions. Additionally, complementary spectroscopic techniques like angle-resolved photoemission or neutron scattering may illuminate collective excitations and electronic structure modifications concomitant with superconductivity. Such multi-pronged approaches will build a more comprehensive picture of these enigmatic states.

In sum, the first unambiguous tunneling spectroscopic identification of the superconducting gap in hydrogen sulfide marks a seminal advance in high-pressure superconductivity science. It solidifies the central role of phonon-mediated Cooper pairing in sustaining superconductivity at record-high temperatures within this material family. Simultaneously, the nuanced deviations from theoretical expectations beckon deeper inquiries into material-specific complexities and the quest for materials surpassing current performance benchmarks.

As experimental methods continue to improve and theoretical models become increasingly sophisticated, the path toward realizing superconductors functional at ambient conditions grows ever clearer. Hydrogen sulfide and its hydride cousins today exemplify the remarkable achievements borne from this synergy of experimental innovation and intellectual exploration, promising a future where lossless electrical conduction could revolutionize energy, transportation, and beyond.

Subject of Research: Superconductivity and superconducting gap characterization in high-pressure hydrogen sulfide (H₃S).

Article Title: Superconducting gap of H₃S measured by tunnelling spectroscopy.

Article References:
Du, F., Drozdov, A.P., Minkov, V.S. et al. Superconducting gap of H₃S measured by tunnelling spectroscopy. Nature (2025). https://doi.org/10.1038/s41586-025-08895-2

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Materials derive their fundamental characteristics from the dynamic behavior of their constituent particles. Electrons dictate electrical conductivity, while phonons — quantized vibrations of the atomic lattice — govern thermal transport. When these electrons and phonons interact, the resulting coupling can give rise to groundbreaking quantum phenomena. Among the most compelling of these is superconductivity — a state marked by zero electrical resistance — often triggered by phonon-mediated electron pairing. Yet, the difficulty in directly measuring how electrons couple to each individual phonon mode has long impeded deeper insights into these mechanisms.

The original Quantum Twisting Microscope, devised two years ago by the research team led by Professor Shahal Ilani, harnessed the properties of atomically thin van der Waals materials as quantum interferometers at its probe tips. Operating at room temperature, this instrument could image electronic wavefunctions with remarkable spatial resolution, mapping the electronic spectra of diverse quantum materials. However, its capabilities to directly resolve the subtle lattice vibrations remained unattainable — until now.

The newly developed cryogenic QTM operates at ultra-low temperatures, enhancing its sensitivity and heralding a paradigm shift in the imaging of phonons. It exploits an inelastic tunneling process between two atomically-thin layers, where electrons passing through emit phonons with precisely controlled energies and momenta. By finely adjusting the voltage bias and the twist angle between the layers, researchers can systematically tune and scan a wide portion of the phonon energy landscape, mapping its complete spectrum in extraordinary detail.

This precise control and detection method illuminate not only the presence of unique phonon modes but also how strongly electrons couple to each of these modes individually. As Dr. John Birkbeck explains, “Our technique transcends traditional phonon spectroscopy by providing quantitative measurements of the electron-phonon coupling strength at the single-mode level across a broad momentum range.” This affords unprecedented insight into the fundamental dynamics underpinning quantum behavior in advanced materials.

The application of this technique to twisted bilayer graphene led to a remarkable and unforeseen discovery: the identification of a distinctive low-energy collective excitation termed the “phason.” Unlike typical phonons, phasons are associated with the relative sliding motion between the two graphene sheets. Notably, the electron-phason coupling intensifies as the twist angle approaches the celebrated magic angle, a configuration known to produce exotic superconducting and strange metallic phases. This link hints that phasons may be central actors in the emergence of these quantum states.

Beyond phonons and phasons, the versatility of the cryogenic QTM promises to open new investigative frontiers. Co-author Jiewen Xiao highlights that the method is broadly applicable to the detection of any collective excitation that couples to tunneling electrons. This capability positions the microscope as a vital tool to probe plasmons, magnons, spinons, and other Goldstone modes within a variety of quantum materials, dramatically expanding our experimental toolkit for condensed matter physics.

As we increasingly seek to unravel the mysteries of quantum materials, tools like the cryogenic QTM become indispensable. The research team, including lead author Alon Inbar, expresses optimism that this technical innovation will catalyze rapid progress in understanding the intricate coupling mechanisms at play and unlock new quantum phases of matter that have thus far eluded comprehensive experimental observation.

The cryogenic QTM’s dual capacity to image both the electronic states and their coupled collective excitations crucially positions it at the intersection of fundamental research and applied quantum technologies. Insights gleaned from this instrument are anticipated to accelerate advancements in quantum computing, high-precision sensing, and emerging quantum electronic devices, where harnessing such intricate electron-boson interactions is essential.

The full implications of this research are vast and ripple across the fields of material science and condensed matter physics. By enabling mode-selective and momentum-resolved measurements of electron-phonon interactions, the QTM facilitates an unparalleled understanding of superconductivity’s microscopic origins and the exotic metallic states that challenge current physics paradigms. This opens doors to engineering materials with custom quantum properties tailored for future technologies.

In summary, the introduction of the cryogenic Quantum Twisting Microscope marks a quantum leap in our investigative capabilities. Its application to twisted bilayer graphene reveals that phasons, this newly observed quantum vibrational mode, may play an essential role in modulating the quantum phases within these atomically engineered structures. As this technology matures, it stands poised not only to deepen our comprehension of existing quantum phenomena but also to uncover entirely new realms of quantum matter.

With every new measurement facilitated by QTM, we get closer to unraveling the complex tapestry of interactions that dictate the behavior of electrons in quantum materials. The researchers’ exploration foreshadows a new era where detailed spectroscopic mapping of collective modes becomes routine, laying the foundation for discoveries that could redefine our technological landscape.

Subject of Research:
Electron-phonon coupling and collective excitations in twisted bilayer graphene studied via cryogenic Quantum Twisting Microscopy.

Article Title:
Quantum twisting microscopy of phonons in twisted bilayer graphene

News Publication Date:
2025

Web References:
Not specified in the source material.

Image Credits:
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Keywords

Phonons, Graphene, Basic research, Discovery research, Superconductivity, Low temperature physics, Measuring instruments, Vibration