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1. Toward an Ab Initio Theory of High-Temperature Superconductors: A Study of Multilayer Cuprates

   https://doi.org/10.1103/PhysRevX.15.021071  

   Bacq-Labreuil, Benjamin; Lacasse, Benjamin; Tremblay, A-M S; Sénéchal, David; Haule, Kristjan (May 2025, Physical Review X)

   Significant progress toward a theory of high-temperature superconductivity in cuprates has been achieved via the study of effective one- and three-band Hubbard models. Nevertheless, material-specific predictions, while essential for constructing a comprehensive theory, remain challenging due to the complex relationship between real materials and the parameters of the effective models. By combining cluster dynamical mean-field theory and density functional theory in a charge-self-consistent manner, here we show that the goal of material-specific predictions for high-temperature superconductors from first principles is within reach. To demonstrate the capabilities of our approach, we take on the challenge of explaining the remarkable physics of multilayer cuprates by focusing on the two representative ${\mathrm{Ca}}_{(1+n)}{\mathrm{Cu}}_n{\mathrm{O}}_{2n}{\mathrm{Cl}}_2$and ${\mathrm{HgBa}}_2{\mathrm{Ca}}_{(n-1)}{\mathrm{Cu}}_n{\mathrm{O}}_{(2n+2)}$families. We shed light on the microscopic origin of many salient features of multilayer cuprates, in particular, the $n$dependence of their superconducting properties. The growth of $T_c$from the single-layer to the trilayer compounds is here explained by the reduction of the charge transfer gap and, consequently, the growth of superexchange $J$as $n$increases. The origin of both is traced to the appearance of low-energy conduction bands reminiscent of standing wave modes confined within the stack of ${\mathrm{CuO}}_2$planes. We interpret the ultimate drop of $T_c$for $n\ge 4$as a consequence of the inhomogeneous doping between the ${\mathrm{CuO}}_2$planes, which prevents the emergence of superconductivity in the inner planes due to their insufficient effective hole doping, as we also highlight the existence of a minimal doping (4%) required for superconductivity to appear in one of the planes. We explain material-specific properties such as the larger propensity of ${\mathrm{HgBa}}_2{\mathrm{Ca}}_{(n-1)}{\mathrm{Cu}}_n{\mathrm{O}}_{(2n+2)}$to superconduct compared with ${\mathrm{Ca}}_{(1+n)}{\mathrm{Cu}}_n{\mathrm{O}}_{2n}{\mathrm{Cl}}_2$. We also find the coexistence of arcs and pockets observed with photoemission, the charge redistribution between copper and oxygen, and the link to the pseudogap. Our work establishes a framework for comprehensive studies of high-temperature superconducting cuprates, enables detailed comparisons with experiment, and, through its settings, unlocks opportunities for theoretical material design of high-temperature superconductors. Published by the American Physical Society2025 

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2. First Measurement of $R\left(X_{\tau /\ell }\right)$ as an Inclusive Test of the $b\to c\tau \nu$ Anomaly

   https://doi.org/10.1103/PhysRevLett.132.211804  

   Adachi, I; Adamczyk, K; Aggarwal, L; Ahmed, H; Aihara, H; Akopov, N; Aloisio, A; Asner, D M; Atmacan, H; Aushev, T; et al (May 2024, Physical Review Letters)

   We measure the tau-to-light-lepton ratio of inclusive $B$-meson branching fractions $R\left(X_{\tau /\ell }\right)\equiv \mathcal{B}(B\to X\tau \nu )/\mathcal{B}(B\to X\ell \nu )$, where $\ell$indicates an electron or muon, and thereby test the universality of charged-current weak interactions. We select events that have one fully reconstructed $B$meson and a charged lepton candidate from $189{\mathrm{fb}}^{-1}$of electron-positron collision data collected with the Belle II detector. We find $R\left(X_{\tau /\ell }\right)=0.228\pm 0.016\left(\mathrm{stat}\right)\pm 0.036\left(\mathrm{syst}\right)$, in agreement with standard-model expectations. This is the first direct measurement of $R\left(X_{\tau /\ell }\right)$. Published by the American Physical Society2024 

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3. Constraints on $f\left(R\right)$ gravity from thermal-Sunyaev-Zel’dovich-effect-selected SPT galaxy clusters and weak lensing mass calibration from DES and HST

   https://doi.org/10.1103/PhysRevD.111.043519  

   Vogt, S_M L; Bocquet, S; Davies, C T; Mohr, J J; Schmidt, F; Ruan, C-Z; Li, B; Hernández-Aguayo, C; Grandis, S; Bleem, L E; et al (February 2025, Physical Review D)

   We present constraints on the $f\left(R\right)$gravity model using a sample of 1005 galaxy clusters in the redshift range 0.25–1.78 that have been selected through the thermal Sunyaev-Zel’dovich effect from South Pole Telescope data and subjected to optical and near-infrared confirmation with the multicomponent matched filter algorithm. We employ weak gravitational lensing mass calibration from the Dark Energy Survey Year 3 data for 688 clusters at $z<0.95$and from the Hubble Space Telescope for 39 clusters with $0.6<z<1.7$. Our cluster sample is a powerful probe of $f\left(R\right)$gravity, because this model predicts a scale-dependent enhancement in the growth of structure, which impacts the halo mass function (HMF) at cluster mass scales. To account for these modified gravity effects on the HMF, our analysis employs a semianalytical approach calibrated with numerical simulations. Combining calibrated cluster counts with primary cosmic microwave background temperature and polarization anisotropy measurements from the Planck 2018 release, we derive robust constraints on the $f\left(R\right)$parameter $f_{R0}$. Our results, ${\log }_{10}\left|f_{R0}\right|<-5.32$at the 95% credible level, are the tightest current constraints on $f\left(R\right)$gravity from cosmological scales. This upper limit rules out $f\left(R\right)$-like deviations from general relativity that result in more than a $\sim 20\%$enhancement of the cluster population on mass scales $M_{200\mathrm{c}}>3\times {10}^{14}{M}_{\odot }$. Published by the American Physical Society2025 

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4. Anomalies in hadronic $B$ decays: An update

   https://doi.org/10.1103/5jp1-7cfw  

   Bhattacharya, Bhubanjyoti; Bouchard, Marianne; Hudy, Luke; Jean, Alexandre; London, David; MacKenzie, Christopher (September 2025, Physical Review D)

   Recently, $B\to PP$decays ( $B=\{B^0,B^{+},B_s^0\}$, $P=\{\pi ,K\}$) were analyzed under the assumption of flavor SU(3) symmetry ( ${\mathrm{SU}\left(3\right)}_F$). Although the individual fits to $\mathrm{\Delta }S=0$or $\mathrm{\Delta }S=1$decays are good, it was found that the combined fit is very poor: there is a $3.6\sigma$disagreement with the ${\mathrm{SU}\left(3\right)}_F$limit of the standard model ( ${\mathrm{SM}}_{{\mathrm{SU}\left(3\right)}_F}$). One can remove this discrepancy by adding ${\mathrm{SU}\left(3\right)}_F$-breaking effects, but 1000% ${\mathrm{SU}\left(3\right)}_F$breaking is required. In this paper, we extend this analysis to include decays in which there is an $\eta$and/or ${\eta }^{\prime }$meson in the final state. We now find that the combined fit exhibits a $4.1\sigma$discrepancy with the ${\mathrm{SM}}_{{\mathrm{SU}\left(3\right)}_F}$, and 1000% ${\mathrm{SU}\left(3\right)}_F$-breaking effects are still required to explain the data. These results are rigorous, group-theoretically—no theoretical assumptions have been made. But when one adds some theoretical input motivated by QCD factorization, the discrepancy with the ${\mathrm{SM}}_{{\mathrm{SU}\left(3\right)}_F}$grows to $4.9\sigma$. 

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5. Leptogenesis during an era of early SU(2) confinement

   https://doi.org/10.1103/nmpt-fwz6  

   Bhalla-Ladd, India; Ginnett, Izzy; Tait, Tim_M P (October 2025, Physical Review D)

   We explore leptogenesis during a cosmological epoch during which the electroweak $\mathrm{SU}(2{)}_L$force is confined. During weak confinement, there is only one conserved nonanomalous global charge, $r$, which is a linear combination of lepton-number, baryon-number, and hypercharge. The inclusion of heavy Majorana neutrinos leads to an $r$-charge and $CP$-violating interaction with a composite scalar, $\mathrm{\Phi }$, and composite fermions, $\mathrm{\Psi }$, allowing for the generation of an $r$-charge asymmetry, which translates into a baryon asymmetry post $\mathrm{SU}(2{)}_L$deconfinement. Determining the resulting baryon asymmetry as a function of the model parameters, we find that the predicted baryon-asymmetry can match observations for a wide swath of parameter space: a weak confinement scale ${\mathrm{\Lambda }}_W\sim {10}^{11}–{10}^{14}\mathrm{GeV}$, the sum of the Standard Model Yukawa couplings $\sum Y_{i\alpha }{Y}_{i\alpha }^{*}\sim {10}^{-2}-{10}^0$, $m_{\mathrm{\Phi }}/m_{\mathrm{\Psi }}\sim 0-0.5$, and a $\mathrm{\Phi }-\mathrm{\Psi }-\mathrm{\Psi }$coupling $\left|g\right|\sim 1$with complex phase ${\theta }_g\sim \pi /4$. While leptogenesis under the assumption of a standard cosmology relies on the complex phase of the neutrino Yukawa couplings, the asymmetry generated in this novel background cosmology primarily depends on a strong phase from $\mathrm{SU}(2{)}_L$confinement, ${\theta }_g$, and favors negligible $CP$-violation in the right-handed neutrino decays. 

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