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Fermi gases, collections of fermions such as neutrons and electrons, are found throughout nature, from solids to neutron stars. Interacting Fermi gases can form a superfluid or, for charged fermions, a superconductor. We have observed the superfluid phase transition in a strongly interacting Fermi gas by high-precision measurements of the local compressibility, density, and pressure. Our data completely determine the universal thermodynamics of these gases without any fit or external thermometer. The onset of superfluidity is observed in the compressibility, the chemical potential, the entropy, and the heat capacity, which displays a characteristic lambda-like feature at the critical temperature T(c)/T(F) = 0.167(13). The ground-state energy is 3/5ξN E(F) with ξ = 0.376(4). Our measurements provide a benchmark for many-body theories of strongly interacting fermions.
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http://dx.doi.org/10.1126/science.1214987 | DOI Listing |
Chem Sci
September 2025
College of Chemistry and Materials Engineering, Wenzhou University Wenzhou Zhejiang 325035 P. R. China
Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) owing to abundant resources and cost-effectiveness. However, cathode materials face persistent challenges in structural stability, ion kinetics, and cycle life. This review highlights the transformative potential of high-entropy (HE) strategies that leveraging multi-principal element synergies to address these limitations entropy-driven mechanisms.
View Article and Find Full Text PDFPNAS Nexus
September 2025
Laboratoire Charles Coulomb (L2C), Université de Montpellier and CNRS (UMR 5221), Montpellier 34095, France.
Active-matter systems are inherently out-of-equilibrium and perform mechanical work by utilizing their internal energy sources. Breakdown of time-reversal symmetry (BTRS) is a hallmark of such dissipative nonequilibrium dynamics. We introduce a robust, experimentally accessible, noninvasive, quantitative measure of BTRS in terms of the Kullback-Leibler divergence in collision events, demonstrated in our novel artificial active matter, comprised of battery-powered spherical rolling robots whose energetics in different modes of motion can be measured with high precision.
View Article and Find Full Text PDFSmall Methods
September 2025
Institute of Applied Mechanics, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei, 106216, Taiwan.
2D lead-halide perovskites have garnered considerable attention owing to their superior environmental stability and tunable optoelectronic properties, which can be precisely controlled through varying quantum well (QW) width (denoted by the integer n). However, the commonly observed phenomenon of mixed QW width distributions poses a major obstacle to achieving optimal device performance, necessitating an in-depth understanding of how QW width distributions depend on chemical composition and thermodynamic stability. In this work, a robust machine learning (ML)-based energy model is developed, rigorously benchmarked against first-principles calculations, enabling extensive molecular-level simulations of 2D perovskites with butylammonium (BA) and phenethylammonium (PEA) spacer cations.
View Article and Find Full Text PDFNatl Sci Rev
September 2025
Institute for Advanced Study in Physics and School of Physics, Zhejiang University, Hangzhou 310058, China.
Exactly solved models provide rigorous understanding of many-body phenomena in strongly correlated systems. In this article, we report a breakthrough in uncovering universal many-body correlated properties of the quantum integrable Lieb-Liniger model. We exactly calculate the dynamical correlation functions by computing the form factors through a newly developed method, by which we are capable of calculating all possible 'relative excitations' over the ground state or a finite temperature state to high precision.
View Article and Find Full Text PDFEntropy (Basel)
August 2025
Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 0200, Australia.
There is much confusion about the apparent opposition between Darwinian evolution and the second law of thermodynamics. Both entropy and entropy production play more fundamental roles in the origin of life and Darwinian evolution than is generally recognized. I argue that Darwinian evolution can be understood as a tendency for entropy production to increase.
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