The kagome geometry is an example of a frustrated configuration in which rich physics takes place, including the emergence of superconductivity and charge density wave (CDW). Among the kagome metals, $\mathrm{S}\mathrm{c}{\mathrm{V}}_{\mathrm{6}}\mathrm{S}{\mathrm{n}}_{\mathrm{6}}$ hosts an unconventional CDW, with its electronic order showing a different periodicity from the leading lattice instability. In this material, a CDW-softened flat phonon band has a second-order collapse at the same time that the first-order transition occurs. This phonon band originates from the out-of-plane vibrations of the Sc and Sn atoms, and it is at the base of the electron-phonon-coupling driven CDW phase of $\mathrm{S}\mathrm{c}{\mathrm{V}}_{\mathrm{6}}\mathrm{S}{\mathrm{n}}_{\mathrm{6}}$. Here we use uniaxial strain to tune the frequency of the CDW amplitude mode, which originates from the collapse of the flat phonon band, tracking its evolution via time-resolved optical spectroscopy and first-principles calculations. Our findings emphasize the capability to induce an enhancement of the unconventional CDW properties in $\mathrm{S}\mathrm{c}{\mathrm{V}}_{\mathrm{6}}\mathrm{S}{\mathrm{n}}_{\mathrm{6}}$ kagome metal through control of strain.

We establish the phase diagram of the Hubbard model on a cubic lattice for a wide range of temperatures, dopings, and interaction strengths, considering both commensurate and incommensurate magnetic orders. We use the dynamical mean-field theory together with an efficient method to compute the free energy which enable the determination of the correct ordering vectors. Besides an antiferromagnetic state close to half filling, we identify a number of different magnetic spiral phases with ordering vectors $(q,\pi ,\pi )$, $(q,q,\pi )$, and $(q,q,q)$, as well as a region with close competition between them, hinting at spatial phase separation or at the onset of a stripe phase. Additionally, we extensively study several thermodynamic properties with direct relevance to cold-atom experiments: the entropy, energy, and double occupancy.

We study a model of contraction-based cell motility inside a microchannel to investigate the regulation of cell polarization and motion by the mechanical resistance of the environment. A positive feedback between the asymmetry of the acto-myosin cortex density and cell motion gives rise to spontaneous symmetry breaking and motility beyond a threshold contractility that depends on the resistance of extracellular medium. In highly viscous environments, we predict bistability under moderate contractility, so that symmetry breaking needs to be activated. In viscoelastic environments, we find the possibility for periodic oscillations in cortex density polarization and velocity. At the boundary between viscous and viscoelastic environments, the cell may cross, bounce back, or become trapped, depending on the viscoelastic relaxation time. These results are summarized in phase diagrams obtained by combining linear stability analysis and numerical simulations.

The axioms of quantum mechanics provide limited information regarding the structure of the Hilbert space, such as the underlying number system. The latter is generally regarded as complex, but generalizations of complex numbers, so-called hypercomplex numbers, cannot be ruled out in theory. Therefore, specialized experiments to test for hypercomplex quantum mechanics are needed. To date, experimental tests are limited to single-particle interference exploiting a closed phase relation in a three-path interferometer called the Peres test. The latter distinguishes complex quantum mechanics from quaternionic quantum mechanics. Here, we propose a general matrix formalism putting the Peres test on a solid mathematical ground. On this basis, we introduce multipath and multiparticle interference tests, which provide a direct probe for any dimension of the number system of quantum mechanics.

Periodically driven systems engender a rich competition between the timescales of the drives and those of the system, leading to a limited ability to describe the system in full. We present a framework for the description of interacting bosonic driven systems via a Floquet expansion on top of a quantization that “counts” the drive photons, and provide compelling arguments for the superior performance of our method relative to standard Floquet approaches. Crucially, our approach extends beyond the rotating wave approximation and addresses the long-standing issue of mismatch between the quantum Floquet formalism and its classical counterpart. We, furthermore, pinpoint key corrections to the positions of multiphoton resonances, which are commonly used in the calibration and operation of qubit architectures.

The branching fraction ratios of ${\overline{B}}^0\to D^{+}{\tau }^{-}{\overline{\nu }}_{\tau }$ and ${\overline{B}}^0\to D^{*+}{\tau }^{-}{\overline{\nu }}_{\tau }$ decays are measured with respect to their muonic counterparts, using a data sample corresponding to an integrated luminosity of $2.0{\mathrm{fb}}^{-1}$ collected by the LHCb experiment in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$. The reconstructed final states are formed by combining $D^{+}$ mesons with ${\tau }^{-}\to {\mu }^{-}{\overline{\nu }}_{\mu }{\nu }_{\tau }$ candidates, where the $D^{+}$ is reconstructed via the $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$ decay. The results are $R(D^{+})=0.249\pm 0.043\pm 0.047$, $R(D^{*+})=0.402\pm 0.081\pm 0.085$, where the first uncertainties are statistical and the second systematic. The two measurements have a correlation coefficient of $-0.39$ and are compatible with the standard model.

We analyze the low-energy dynamics of gap-between-jets cross sections at hadron colliders, for which phase factors in the hard amplitudes spoil collinear cancellations and lead to double (“super-leading”) logarithmic behavior. Based on a method-of-regions analysis, we identify three-loop contributions from perturbative active-active Glauber-gluon exchanges with the right structure to render the cross section consistent with PDF factorization below the gap veto scale. The Glauber contributions we identify are unambiguously defined without regulators beyond dimensional regularization.

Cross sections for electron impact dissociative excitation and ionization in scattering on vibrationally excited levels of the ground electronic state of ${\mathrm{H}}_3^{+}$ and its isotopologues are reported in the energy range of 8 to 1000 eV. Calculations have been performed using a newly developed version of the molecular convergent close-coupling code. Cross sections for total dissociative excitation, ionization yielding atomic fragments such as ${\mathrm{D}}^{+}$, and the total inelastic cross section are presented. Good agreement with available experiments has been demonstrated.

We investigate the moiré band structures and a possible even-denominator fractional quantum Hall state in small angle twisted bilayer ${\mathrm{MoTe}}_2$, using combined large-scale local basis density functional theory calculation and continuum model exact diagonalization. Via large-scale first-principles calculations at $\theta =1.89°$, we find a sequence of $C=1$ (Chern number in the K valley) moiré Chern bands in analogy to Landau levels. By constructing the continuum model with multiple Chern bands, we undertake a band-projected exact diagonalization using an unscreened Coulomb repulsion to identify possible non-Abelian states near twist angle $\theta =1.89°$ at the half filling of second moiré band.

Based on the first-principles calculations coupled with the Bethe-Salpeter equation, the topological exciton density wave is investigated in two-dimensional monolayer ${\mathrm{WSe}}_2$. We find that the topological excitonic insulator phase can exist in monolayer ${\mathrm{WSe}}_2$, and it is robust against in-plane strain. In this system, the energy minimum of exciton bands is shifted to a finite in-plane momentum, forming a Fulde-Ferrell-Larkin-Ovchinnikov-like state. Using the Gross-Pitaevskii equations, stripe-patterned exciton density waves with a nonzero velocity emerge in monolayer ${\mathrm{WSe}}_2$. Our findings pave a new way for exploring the interplay between electron correlation and nontrivial topology.

We report our discovery of a temperature-independent anomalous Hall effect (AHE) from 15 mK to 300 K temperature occurring in a pure bismuth transport device whose average thickness is 68 nm. This surprising behavior is accompanied with an expected temperature-dependent longitudinal resistance consistent with semimetallic bismuth. However, it surprisingly showed no hint of a magnetoresistance for magnetic fields between $\pm 30\mathrm{T}$. Even though bismuth is a diamagnetic material that a priori does not break time-reversal symmetry, our analysis of the reconstructed conductivities points toward the AHE to be of the intrinsic type that does not emanate from magnetic impurities. Finally, as pure bismuth has been shown numerically to host a Berry curvature at its surface that breaks inversion symmetry, we propose it as a possible explanation for the temperature-independent AHE observed here.

${\mathrm{PtSe}}_2$ is a van der Waals material transitioning from an indirect band gap semiconductor to a semimetal with increasing thickness. Its absorption threshold has been conjectured to originate from interband indirect transitions. By quantitative comparison between broadband (0.8–3.0 eV) optical absorption of high-quality exfoliated crystals and DFT ab initio simulations, we prove instead that the optical absorption arises only from direct transitions. This understanding allows us to shed light on the semiconductor-to-semimetal transition in an emblematic strongly thickness-dependent 2D material, and to explore the effect of stacking and excitons on the optical absorption.

The control of antiferromagnets with ultrashort optical pulses has emerged as a prominent field of research. Tailored laser excitation can launch coherent spin waves at terahertz frequencies, yet a comprehensive description of their generation mechanisms is still lacking despite extensive efforts. Using terahertz emission spectroscopy, we investigate the generation of a coherent magnon mode in the van der Waals antiferromagnet ${\mathrm{NiPS}}_3$ under a range of photoexcitation conditions. By tuning the pump photon energy from transparency to resonant with a $d\text{−}d$ transition, we reveal a striking change in the coherent magnon’s dependence on the pump polarization, indicating two distinct excitation mechanisms. Our findings provide a strategy for the manipulation of magnetic modes via photoexcitation around subgap electronic states.

Among the most iconic features of classical dissipative dynamics are persistent limit-cycle oscillations and critical slowing down at the onset of such oscillations, where the system relaxes purely algebraically in time. On the other hand, quantum systems subject to generic Markovian dissipation decohere exponentially in time, approaching a unique steady state. Here we show how coherent limit-cycle oscillations and algebraic decay can emerge in a quantum system governed by a Markovian master equation as one approaches the classical limit, illustrating general mechanisms using a single-spin model and a two-site lossy Bose-Hubbard model. In particular, we demonstrate that the fingerprint of a limit cycle is a slow-decaying branch with vanishing decoherence rates in the Liouville spectrum, while a power-law decay is realized by a spectral collapse at the bifurcation point. We also show how these are distinct from the case of a classical fixed point, for which the quantum spectrum is gapped and can be generated from the linearized classical dynamics.

The quantum kinetic evolution of neutrinos in dense environments, such as the core-collapse supernovae or the neutron star mergers, can result in fast flavor conversion (FFC), presenting a significant challenge to achieving robust astrophysical modeling of these systems. Recent works that directly simulate the quantum kinetic transport of neutrinos in localized domains have suggested that the asymptotic outcome of FFCs can be modeled by simple analytical prescriptions when coarse grained over a size much larger than the FFC length scale. In this Letter, by leveraging such a scale separation, we incorporate the analytical prescriptions into global simulations that solve the classical neutrino transport equation including collisions and advection under spherical symmetry. We demonstrate that taking this approach allows to obtain results that quantitatively agree with those directly from the corresponding global quantum kinetic simulations and precisely capture the collisional feedback effect for cases where the FFC happens inside the neutrinosphere. Notably, the effective scheme does not require resolving the FFC time and length scales, hence only adds negligible computational overhead to classical transport. Our work highlights that efficient and robust integration of FFCs in classical neutrino transport used in astrophysical simulation can be feasible.

The identity of dark matter has been a mystery in astronomy, cosmology, and particle theory for about a century. We present the first dark matter search with a high-dispersion spectrograph by using WINERED at the 6.5 m Magellan Clay telescope to measure the photons from the dark matter decays. The dwarf spheroidal galaxies (dSphs) Leo V and Tucana II are observed by utilizing an object-sky-object nodding observation technique. Employing zero consistent flux data after the sky subtraction and performing Doppler shift analysis for further background subtraction, we have established one of the most stringent limits to date on dark matter lifetime in the mass range of 1.8–2.7 eV. The conservative bound is translated to the photon coupling, $g_{\varphi \gamma \gamma }$ for axionlike par ticles around $g_{\varphi \gamma \gamma }\lesssim (2–3)\times {10}^{-11}{\mathrm{GeV}}^{-1}$ (${10}^{-10}{\mathrm{GeV}}^{-1}$) for the case that ultrafaint dSphs have the Navarro-Frenk-White (generalized Hernquist) dark matter profile.

Mass measurements of ${}^{31–33}\mathrm{Na}$ and ${}^{31–35}\mathrm{Mg}$ using the TITAN MR-TOF-MS at TRIUMF’s ISAC facility are presented, with the uncertainty of the ${}^{33}\mathrm{Na}$ mass reduced by over 2 orders of magnitude. The excellent performance of the MR-TOF-MS has also allowed the discovery of a millisecond isomer in ${}^{32}\mathrm{Na}$. The precision obtained shows that the binding energy of the normally closed $N=20$ neutron shell reaches a minimum for ${}^{32}\mathrm{Mg}$ but increases significantly for ${}^{31}\mathrm{Na}$, hinting at the possibility of enhanced shell strength toward the unbound ${}^{28}\mathrm{O}$. We compare the results with new ab initio predictions that raise intriguing questions of nuclear structure beyond the dripline.