Unconventional superconductivity from lattice quantum disorder

arXiv:2602.03576 · cond-mat.supr-con · Submitted 2026-02-03 · Read on arXiv

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Introduction to the show: ident: Quantum Radio. Generated commentary on the latest quantum physics and condensed matter papers.

Kai: I'm Kai, and with me are Mira and Lev, guest researcher.

Mira: Today's paper: "Unconventional superconductivity from lattice quantum disorder".

Kai: The gist By incorporating nuclear quantum many-body effects within first-principles calculations, this work discovers a lattice quantum disordered phase in superconductors H3S and La3Ni2O7,

Mira: First, who's behind it and why it matters.

Title and authors: Kai: We're moving into how this paper suggests we can use these findings to predict and discover new superconductors based on the "Unconventional superconductivity from lattice quantum disorder." The core idea here is using the LQD phase as a target for material screening.

Mira: Right, it’s about identifying materials that naturally host a large LQD phase, which they suggest is a practical route for predicting higher Tc. It’s not just about finding any superconductor; it's about finding ones with this specific lattice feature.

Lev: From an error correction viewpoint, if we can screen for these materials, we know exactly what kind of structural instability to expect in the low-temperature regime when you try to cool them down.

Kai: They are using the framework established across H3S and La3Ni2O7 as a template. If a new material shows signs of having that LQD phase region in its P-T diagram, it becomes a strong candidate for having high Tc superconductivity.

Mira: And they also touch on doping dependence here. They propose that doping will influence the soft mode on the potential energy surface in a manner analogous to pressure, which is relevant for cuprates and other families where we tune carriers to get higher temperatures.

Lev: That analogy with pressure suggests that controlling carrier concentration might be just as important as changing external pressure when you are trying to optimize the superconducting state in these systems.

Kai: So the paper gives us a two-step roadmap: first, find materials with a large LQD phase, and second, then consider introducing carriers to see how that affects the superconducting properties.

Mira: It’s an interesting way to approach high Tc families like cuprates because it grounds the search in specific lattice physics rather than just broad electronic tuning.

Lev: It gives us a concrete target for theoretical work—we don't just look at abstract electron interactions; we look for these specific quantum disorder signatures.

Kai: So, the paper suggests that this LQD framework should be used to guide the search for new superconductors with higher Tc, focusing on materials that exhibit this lattice quantum disorder.

The paper's summary: Kai: Now we're going back to what the paper actually summarized in "Unconventional superconductivity from lattice quantum disorder." It boils down to this: conventional theories overlook the rich physics of the lattice, and by including nuclear many-body effects, they find a lattice quantum disordered phase.

Mira: So, they’re saying that when you include these nuclei properly, you see that the system doesn't just transition smoothly; it goes through a regime where quantum fluctuations stabilize a higher-symmetry state because of on-site nuclear tunneling competing with inter-site interactions.

Lev: Essentially, the competition between those two forces—tunneling and interaction—is what creates this LQD phase, which is the structural change we’re talking about.

Kai: And this phase is what dictates the structural phase boundary in their P-T diagram, and it lines up with where superconductivity starts on that left side of the dome. It’s not just a coincidence; it's a direct connection between the lattice disorder and the superconducting state itself.

Mira: The summary emphasizes that this coincidence is most telling because Tmaxc,LQD for H3S at two hundred twenty K matches its peak Tc, and similarly for La3Ni2O7 at eighty K <ref:2602.03576#pg2>. That temperature matching is what provides the strongest evidence of the mechanism.

Lev: If you think about it in terms of running experiments, this means that if you want to measure the structural instability, you have to be prepared for these quantum fluctuations to be significant at those critical temperatures.

Kai: And it confirms that superconductivity occurs entirely within the high-symmetry Im¯3m phase, which is a very specific constraint on where the physics actually happens <ref:2602.03576#pg2>.

Mira: So, in simple terms, they’re saying that unconventional superconductivity on the left flank of these domes isn't just an electronic thing; it’s fundamentally tied to a quantum order-disorder transition within the lattice.

The paper's improvements: Kai: Moving on to what they suggest as improvements to this research, they are essentially suggesting that we need a more rigorous way of identifying phase transitions by looking at the curvature of the free-energy surface.

Mira: They’re saying the true phase transition point must be identified by examining the curvature of that free-energy surface that accounts for both thermal and quantum effects, not just looking at where a single frequency changes sign. That’s a more complete way to define instability.

Lev: If we were building an error correction scheme, knowing you need to check the full curvature means your model has to handle complex energy landscapes, not just simple harmonic approximations.

Kai: This leads directly into how they map the boundaries using path-integral molecular dynamics, or PIMD, combined with machine learning interatomic potentials at the DFT level to build that surface. That’s a sophisticated computational tool they're advocating for.

Mira: They are suggesting this integrated approach—DFT potentials feeding PIMD to map out the free-energy surface—is the way forward because it captures both thermal and quantum effects together, which is what allows them to get those precise boundary lines matching experimental data.

Lev: That method sounds computationally expensive, but if it gives you these precise phase boundaries that align with experiment, then it’s a necessary tool for validating any new theory about structural instability in these materials.

Kai: The main improvement they highlight is this unified framework—using PIMD to construct the free-energy surface and comparing that boundary against classical MD results to define the LQD region.

Conclusion: Kai: So, summarizing the whole thing on "Unconventional superconductivity from lattice quantum disorder," the main point is that we’ve established that superconductivity on the left flank of these domes originates from a quantum order-disorder transition into this lattice quantum disordered phase.

Mira: That LQD phase is stabilized by nuclear tunneling at low temperatures, and its maximum temperature Tmaxc,LQD coincides exactly with the peak superconducting temperature Tmaxc,SC for both H3S and La3Ni2O7.

Lev: From my perspective on what this means for implementation, it confirms that we need models capable of handling these quantum fluctuations when designing experiments or theoretical models for structural transitions in these materials.

Kai: And the authors conclude that this suggests a practical route for predicting and discovering superconductors with higher Tc: first, identify materials that host a large LQD phase, then consider appropriate carrier introduction.

Mira: The overall implication is that the LQD framework could be widespread, and it’s expected to remain relevant for doping-dependent high-Tc families like the cuprates as we look for new superconducting materials.

Lev: And ultimately, this work provides a unified framework for understanding unconventional superconductivity by emphasizing the role of lattice quantum disorder.

Kai: That's all on "Unconventional superconductivity from lattice quantum disorder." We’ll take a quick break and come back after the break to discuss how this LQD phase might relate to other phenomena.

State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Peking University · Interdisciplinary Institute of Light-Element Quantum Materials, Peking University

cond-mat.supr-con

Submitted: 2026-02-03

Updated: 2026-07-29

Journal ref: Phys. Rev. Lett. 137, 146001 (2026)

DOI: 10.1103/r8fj-4t94

License: http://creativecommons.org/licenses/by/4.0/

Importance score: 92/100

The gist: The gist By incorporating nuclear quantum many-body effects within first-principles calculations, this work discovers a lattice quantum disordered phase in superconductors H3S and La3Ni2O7, which

Key concepts

Lattice Quantum Disordered Phase (LQD): This is a specific state found in superconductors where quantum fluctuations stabilize a higher-symmetry disordered structure. Unlike simple thermal disorder, this phase arises from the quantum mechanical nature of the nuclei, leading to lattice dynamics beyond standard phonon models.
Nuclear Quantum Many-Body Effects: The study rigorously included these effects in calculations using first principles. These effects account for how the nuclei behave collectively at low temperatures through quantum tunneling and interactions, which is crucial for accurately mapping structural phase boundaries.
Free-Energy Surface (FES): This surface is constructed using the centroid potential of mean force derived from Path Integral Molecular Dynamics (PIMD). It represents the total energy landscape that governs both thermal and quantum effects, allowing researchers to map out structural transitions accurately.
Superconducting Dome Flank: The superconducting dome represents the range of temperatures where superconductivity occurs. The left flank of this dome is linked directly to the LQD phase boundary, indicating that superconductivity on this side originates from a quantum order-disorder transition into the LQD state.

Terminology

Many-Body Effects — 11× in this paper · explained in 2 episodes
Phase Transitions — 6× in this paper · explained in 2 episodes
Ab Initio — 3× in this paper · explained in 1 episode
Unified Framework — 3× in this paper · explained in 5 episodes
Accuracy — 1× in this paper · explained in 1 episode
Bayesian Inference — 1× in this paper · explained in 5 episodes
Core — 1× in this paper · explained in 2 episodes
DFT Calculations — 1× in this paper · explained in 2 episodes
Entanglement — 1× in this paper · explained in 3 episodes

Summary

The gist

By incorporating nuclear quantum many-body effects within first-principles calculations, this work discovers a lattice quantum disordered phase in superconductors H3S and La3Ni2O7, which occupies a triangular region in the P −T phase diagram whose left boundary aligns precisely with Tc of the left flank of the superconducting dome.

Lattice Quantum Disordered Phase Discovery

The research introduces a lattice quantum disordered (LQD) phase in superconductors H3S and La3Ni2O7 by rigorously including nuclear quantum many-body effects within a first-principles framework. This regime is characterized by quantum fluctuations stabilizing a higher-symmetry disordered state, giving rise to lattice dynamics beyond the conventional phonon picture. The structural phase boundary is determined by the free-energy surface, which is constructed by the centroid potential of mean force from PIMD. The boundary obtained via this approach coincides precisely with the left flank of the superconducting dome.

Phase Diagram Mapping and Key Coincidences

The extent of this LQD phase increases linearly with decreasing temperature, with its origin, which we label as Tmaxc,LQD, locating at ∼220 K for H3S. These values align exactly with their respective highest observed superconducting transition temperatures Tcmaxc,SC. The intersection of the PIMD and MD boundaries gives a maximum Tc of about 77 K for the LQD phase of La3Ni2O7 at the PBE level, in consistence with the experimental maximum of superconducting Tc of 80 K.

Mechanism Linking LQD to Superconductivity

The structural transition on the left flank stems from the structural transition of a low-symmetry phase into a LQD phase. The left boundary of the LQD phase aligns with the left flank of the dome. This indicates that superconductivity occurs entirely within the high-symmetry Im¯3m phase. The Tmaxc,LQD coincides precisely with the peak superconducting temperature Tcmaxc,SC for both H3S and D3S. This agreement establishes a direct mechanistic link between the LQD phase and unconventional superconductivity.

Implications and Future Directions

The findings suggest that the right flank of the dome extends from the multicritical point, indicating a profound connection between LQD and the unconventional superconducting mechanism. This picture suggests a practical route for predicting and discovering superconductors with higher Tc: first identify materials that host a large LQD phase, and subsequently consider appropriate carrier introduction. The LQD framework is expected to remain relevant for doping-dependent high-Tc families such as the cuprates. The absence of superconductivity in the antiferromagnetic phase may precisely correspond to the lack of soft modes in the underdoped regime. The LQD phase could be a widespread phenomenon, with its extent varying across different materials. The energy scale of lattice dynamics is comparable to the Tc of high-temperature superconductors.

Summary

The paper establishes that superconductivity on the left flank of the dome originates from a quantum order-disorder transition into a lattice quantum disordered phase. This LQD phase is stabilized by nuclear tunneling in low temperatures, and its maximum temperature Tmaxc,LQD coincides exactly with the peak superconducting temperature Tcmaxc,SC. This coincidence points to a mechanism inherent to the LQD phase that determines the maximum superconducting transition temperature. The study uses path-integral molecular dynamics (PIMD) combined with machine learning interatomic potentials at the DFT level to construct a free-energy surface (FES) that captures both thermal and quantum effects. This framework successfully maps the LQD phase in H3S and La3Ni2O7, confirming that superconductivity occurs entirely within the high-symmetry Im¯3m phase. This work provides a unified framework for understanding unconventional superconductivity by emphasizing the role of lattice quantum disorder.

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Unconventional superconductivity presents a defining challenge in physics. Prevailing theoretical frameworks have predominantly emphasized electrons, largely neglecting the rich physics inherent in the lattice. Conventional phonon theory omits quantum many-body effects of the nuclei, leading to misleading structural phase diagrams and an unsound foundation for superconducting theory. Here, by incorporating nuclear quantum many-body effects within first-principles calculations, we discover a lattice quantum disordered phase in superconductors H3S and La3Ni2O7. This phase occupies a triangular region in the P −T phase diagram, whose left boundary aligns precisely with Tc of the left flank of the superconducting dome.

Improvements for AI systems

textbfReal-time Phase Diagram Mapping for Unconventional Superconductors + Improved AI System Capabilities: The system can now predict structural phase boundaries and identify superconductivity origins by comparing PIMD and MD phase boundaries, as the paper states: "The boundary obtained via this approach coincides precisely with the left flank of the superconducting dome. Its intersection with the classical boundary from conventional molecular dynamics (MD) delineates the region of the LQD phase."
textbfMechanistic Link Verification for High-Temperature Superconductivity + Improved AI System Capabilities: The system can now establish a direct mechanistic link between lattice quantum disorder and pairing by confirming that Tmaxc,LQD coincides precisely with the peak superconducting temperature Tmaxc,SC for both H3S and D3S, which establishes a direct mechanistic link between the LQD phase and unconventional superconductivity.
textbfModel-Free Structural Instability Criterion + Improved AI System Capabilities: The system can now determine structural instability by examining the curvature of the free-energy surface, as it states: the true phase transition point must be identified by examining the curvature of the FES that fully accounts for both thermal and quantum effects.
textbfMaterial Screening for Novel Superconductors + Improved AI System Capabilities: The system can now screen new materials by identifying candidates that host a large LQD phase, providing a practical route for predicting and discovering superconductors with higher Tc by leveraging the framework established across H3S and La3Ni2O7.
textbf Doping-Dependent High-Tc Prediction + Improved AI System Capabilities: The system can now predict the influence of doping on superconductivity by proposing that doping will influence the soft mode on the potential energy surface in a manner analogous to pressure, suggesting an application for cuprates where the LQD framework is expected to remain relevant for doping-dependent high-Tc families.

Abstract

Unconventional superconductivity presents a defining and enduring challenge in condensed matter physics. Prevailing theoretical frameworks have predominantly emphasized electronic degrees of freedom, largely neglecting the rich physics inherent in the lattice. Although conventional phonon theory offers an elegant description of structural phase diagrams and lattice dynamics, its omission of nuclear quantum many-body effects results in misleading phase diagram interpretations and, consequently, an unsound foundation for superconducting theory. Here, by incorporating nuclear quantum many-body effects within first-principles calculations, we discover a lattice quantum disordered phase in superconductors H3S and La3Ni2O7. This phase occupies a triangular region in the pressure-temperature phase diagram, whose left boundary aligns precisely with Tc of the left flank of the superconducting dome. The Tcmax of this quantum disordered phase coincides with the maximum of superconducting Tc, indicating this phase as both the origin of superconductivity on the dome's left flank and a key ingredient of its pairing mechanism. Our findings advance the understanding of high-temperature superconductivity and establish the lattice quantum disordered phase as a unifying framework, both for predicting new superconductors and for elucidating phenomena in a broader context of condensed matter physics.

Sources

The quantum nature of the superconducting hydrogen sulfide at finite temperatures