Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.22134

Putting a Temperature on Electron Correlation

Paul G. Graf·Florian Matz·Markus Penz·Christian Schilling
View original source ↗Read source document ↗Export metadata ↓

Abstract

It is common wisdom that a better understanding of how to quantify electron correlation should lead to more efficient treatments of the correlation problem. Here, we not only substantiate this view but turn it into a concrete, systematic framework for ground states. Since prominent correlation measures such as the nonfreeness depend only on the one-particle reduced density matrix, modeling the correlation energy as a function of such a measure naturally places the framework within reduced density matrix functional theory, while keeping the cost at mean-field level. Strikingly, the variable conjugate to the measure emerges as a ``correlation temperature'', thereby connecting correlation measures, functional theory, and effective temperatures. The framework rationalizes methods such as i-DMFT, and we illustrate its key concepts analytically for the Hubbard dimer and numerically for small molecular systems. This brings a fundamental question within reach: how much of the correlation problem can be solved at mean-field cost?

Explore related subjects

cond-mat.str-elphysics.chem-phquant-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Paul G. Graf, Florian Matz, Markus Penz, Christian Schilling. 2026-10-15. Putting a Temperature on Electron Correlation. https://arxiv.org/abs/2610.22134

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Dark Matter Axions Modulate Dark State Scintillation

The decay rate of the thallium-iodine dark state in the popular alkali-halide scintillator NaI(Tl) modulates in phase with the dipole anisotropy of the cosmic microwave background (CMB), it is argued. Axion dark matter particles --- at rest in the local CMB rest-frame --- couple to the static magnetic field created in their rest-frame by the static electric quadrupole field within the tetragonally-distorted thallium-iodine octahedron surrounding each dark state. For axions with rest-mass energy near the roughly 0.5 eV dark state activation energy in NaI(Tl), the resulting near-infrared electric field created by this axion electrodynamic interaction modulates the dark state scintillation lifetime by bringing home the excited hole --- from the four in-plane iodine 5p orbitals that share it --- to the Tl 6s shell where it can recombine with the excited Tl 6p electron to produce the scintillation light.

cond-mat.str-el↗
arXiv2026

Anomalous Thermal Conductivity Reversal Driven by a Fluctuating Charge Density Wave

For more than a century, the lattice thermal conductivity of crystalline solids has been known to decrease with increasing temperature, as the phonons that carry heat scatter more strongly via Umklapp processes. Here we report a pronounced violation of this rule in the layered charge-density-wave (CDW) metal 2H-TaSe2. Its in-plane thermal conductivity is strongly nonmonotonic: it peaks sharply at the 122 K ordering transition, collapses to a deep minimum near 210 K, and then anomalously reverses, rising with temperature to at least 350 K. Such a high-temperature reversal, in which a crystal conducts heat more efficiently as it is heated, is rare in crystalline solids. Its thermal conductivity minimum lies deep in the disordered phase well above the ordering transition, unlike the weak, transition-centered anomalies of other charge-density-wave systems, pointing to heat conduction governed by fluctuating rather than established order. Combining inelastic X-ray scattering, selected-area electron diffraction, and synchrotron X-ray diffraction, we attribute the reversal to phonons scattering off persistent, fluctuating charge order that survives more than 150 K above the long-range transition, to at least 300 K. A phenomenological phonon-CDW scattering model, tied directly to the measured diffraction linewidth and intensity, quantitatively reproduces the entire nonmonotonic curve. We also reveal that the charge order melts not abruptly but through a fluctuation- and defect-driven, weak first-order process, leaving short-range correlations far above the transition. This work establishes fluctuating charge order as a sensitive control knob for thermal transport in quantum materials and thermal conductivity as a powerful probe of the hidden charge order.

cond-mat.str-el↗
arXiv2026

Symmetry-twisted multi-entropies: Order parameters for 2D SPT phases

Although symmetry-protected topological phases (SPTs) can be distinguished by their entanglement properties, it has been unclear how to extract this information directly from expectation values beyond the 1D case. Here, we close this gap and propose a pair of nonlocal order parameters that can detect and distinguish all bosonic SPTs in 2D protected by internal discrete, Abelian unitary symmetries. The desired topological invariants are extracted by these quantities by effectively simulating the SPT path integral on topologically non-trivial spacetime manifolds. Our order parameters are defined in terms of expectation values of partial symmetry and permutation operations acting on fixed numbers of replicas of the system in finite spatial regions. These expectation values correspond to symmetry-twisted versions of multipartite entanglement quantities known as multi-entropies. We show explicitly that our two order parameters detect symmetry-protected four-party and six-party entanglement, respectively, and we constrain possible "spurious" contributions. We analytically test our proposal in fixed-point lattice models. Our results suggest multipartite entanglement to be a defining feature of SPTs; indeed, we expect our methods to generalize to fermionic and higher-dimensional systems.

cond-mat.str-el↗