We detect entanglement partitions of multipartite quantum systems by exploiting their inherent symmetries. Structures like genuinely multipartite entanglement, m -separability, and entanglement depth are detected as very special cases. This formulation enables us to characterize all entanglement partitions of all three- and four-partite states and witnesses with unitary and permutation symmetry, which we denote Schur-Weyl isotypic witnesses. In particular, we find and parametrize a complete set of bound entangled states therein. For larger systems, we provide a large family of analytical witnesses detecting multipartite states of arbitrary size where none of the parties is separable from the rest. The proposed method relies on weak Schur sampling with projective measurements onto isotypic components and can be implemented in a quantum computer. Beyond physics, our results extend to the mathematical literature: we establish new inequalities between matrix immanants, which constitute an open problem, and characterize the set of such inequalities for matrices of sizes three and four.
We present the thermopower of EuCd 2 P 2 , a material which exhibits a large resistivity peak with significant magnetic field dependence in the temperature range of 10–25 K. In the same region, we observe a highly unusual behavior of the thermopower with two sign changes and giant extrema. The overall variation of the thermopower exceeds 4000 μ V / K and takes place in an extremely narrow temperature region of less than 5 K. The anomaly is suppressed completely in a small magnetic field of 0.5 T. We discuss this observation using a simple drift-diffusion picture and taking into account that the temperature gradient inducing the thermopower voltage is accompanied by a gradient of the electrical resistivity. Our simple estimation yields the correct magnitude, shape, and field dependence of the thermopower anomaly observed in EuCd 2 P 2 . These results open a new route to giant thermopower values via gradients of electronic properties.
Laser wakefield accelerators are bright, compact sources of synchrotronlike x-rays. By driving the wakefield using a 110 TW laser in a variable length gas cell, we are able to map the evolution of the electron beam and resulting x-ray emission. We find that using a laser pulse initially focused to larger than the matched spot size and extending the plasma length beyond the depletion length, dramatically increases the x-ray flux. Self-injected electrons are initially accelerated to > 2 GeV , emitting x-rays with critical energy E c > 20 keV . But, as these electrons dephase, a second high-charge electron bunch is produced and accelerated to ≈ 0.7 GeV . The x-rays produced by this bunch dominate the total emission with > 5 × 10 10 photons per shot with E c = 12 – 17 keV and a flux of 7 × 10 4 photons / mrad 2 / 0.1 % BW . Combining electron and x-ray measurements reveals that the increased emission results from the larger betatron amplitude of the secondary bunch. Simulations attribute this to rapid bubble expansion driven by laser compression over the depletion length, which leads to injection of a high-charge electron bunch with increased transverse momentum and thus stronger betatron radiation.
A search for Higgs boson ( H ) production in association with two vector bosons ( V = W , Z ) via vector-boson scattering (VBS) is presented using proton-proton collision data collected at s = 13 TeV by the CMS experiment, corresponding to an integrated luminosity of 138 fb − 1 . Events containing two forward jets consistent with VBS, a large-radius jet from the decay of a boosted H to a pair of b quarks, and zero, one, or two charged leptons coming from V decays are selected. The process is excluded at 95% confidence level for observed (expected) values of the V V H H coupling modifier κ 2 V outside the interval 0.40 < κ 2 V < 1.60 ( 0.34 < κ 2 V < 1.66 ), assuming standard model values for all other couplings, thus establishing a novel probe of the V V H H interaction. Constraints are also set on the individual κ 2 W and κ 2 Z coupling modifiers and on the allowed region in the κ 2 W − κ 2 Z plane.
We show theoretically that weak quantum fluctuations induced by a nonsymmetric electromagnetic environment may lead to a quantized transconductance of a multiterminal quantum contact rather than to a blockade of transport in the contact. The result suggests the possibility to realize quantum Hall phenomenology without its common ingredients and/or a topological quantum state.
We study ultrafast magneto-photocurrents in a three-dimensional topological insulator. For this purpose, we excite ( In r Bi 1 − r ) 2 Se 3 thin films with a femtosecond laser pulse in the presence of an external magnetic field B ext up to 0.3 T parallel to the film plane. The resulting in-plane photocurrent is measured by detecting the emitted terahertz electromagnetic pulse. It is proportional and perpendicular to B ext . Strikingly, for r ≥ 4 % , we observe an abrupt photocurrent reduction, which is strongly correlated with the indium-induced quenching of the topological surface states. The rise time, decay time, and amplitude of the terahertz magneto-photocurrent can consistently be explained by the following scenario: optically excited spin-polarized electrons propagate toward the film surface where the accumulated spin is converted into an in-plane charge current due to spin-velocity locking. Our results are highly relevant for contact-free probing of spin-charge conversion in systems without spontaneous magnetic order and without having to add invasive spin-source layers.
Near-field enhancement in nanocavities governs the efficiency of nonlinear optical processes and ultrafast light-matter interactions. However, maximizing the cavity quality factor does not necessarily maximize the response under femtosecond excitation. Here, we experimentally demonstrate that hybrid metal-dielectric metasurfaces provide a practical platform for optimizing this trade-off. By coupling a low-Q localized surface plasmon resonance of Au nanodisks to a high-Q dielectric mode of a TiO 2 metasurface, we continuously tune the Q factors of the hybrid modes over a broad range while preserving the plasmonic hotspot geometry. Using four-photon photoemission electron microscopy under 100-fs excitation, we map the nonlinear near-field response and correlate it with spectrally extracted Q factors and ultrafast dynamics measured by time-resolved photoemission electron microscopy. The response varies nonmonotonically with Q and reaches a maximum at Q ≈ 2 0 , where the photoemission yield is enhanced approximately 15-fold relative to the uncoupled metasurface. These results identify pulse-cavity Q-factor matching between the cavity and the driving pulse as a key design principle for pulsed-laser nanophotonics.
We apply a tag-and-probe method to precisely measure the absolute branching fraction of the decay η_{c}→γγ with the BESIII experiment at BEPCII. Starting with a large initial sample of (2712.4±14.3)×10^{6} ψ(3686) events, a sample of 0.16×10^{6} η_{c} events is tagged via the golden channel ψ(3686)→π^{0}h_{c}, h_{c}→γη_{c}, effectively avoiding interference effects. The absolute branching fraction of η_{c}→γγ is measured for the first time to be B(η_{c}→γγ)=(2.45±0.48_{stat}±0.09_{syst})×10^{-4}. Using the world average value of the total width of the η_{c}, the partial decay width of η_{c}→γγ is calculated to be Γ(η_{c}→γγ)=(7.48±1.48_{stat}±0.30_{syst}) keV.
Energetic quarks and gluons traversing a hot and dense quark-gluon plasma deposit energy and momentum into the medium before hadronizing to collimated sprays of particles, known as jets. This energy-momentum deposition is expected to produce medium responses, collectively known as jet wakes, with "diffusion wake" denoting a depletion of particles in the direction opposite to the propagating jet. The diffusion wake is studied by comparing dijet-hadron correlations measured in lead-lead (PbPb) and proton-proton (pp) collisions. The analysis uses PbPb and pp data recorded at a nucleon-nucleon (NN) center-of-mass energy sqrt[s_{NN}]=5.02 TeV with the CMS detector at the CERN LHC. By exploring how the dijet-hadron correlation distributions differ for various pseudorapidity separations of the two jets in the dijet, the presence of a jet diffusion wake is firmly established. The diffusion wake signal has a significance greater than 5 standard deviations for charged particles in the transverse momentum range 1<p_{T}<2 GeV. The measurements are compared with model predictions with and without jet wake effects, providing new insights into quark-gluon plasma properties and the formation of jet-induced wakes.
We report the first searches for charged-lepton-flavor violation in decays of χ_{bJ}(1P) (J=0, 1, and 2) to a pair of charged leptons using 158 million ϒ(2S) decays collected with the Belle detector in e^{+}e^{-} collisions at the KEKB collider. No significant signal is observed, and we set upper limits on the branching fractions for χ_{bJ}(1P) decays to e^{±}μ^{∓} at the level of 10^{-6} and to e^{±}τ^{∓} or μ^{±}τ^{∓} at the level of 10^{-5}. Limits on χ_{b0}(1P) decays are translated into bounds on the corresponding Wilson coefficients of scalar operators that mediate charged-lepton-flavor violation.
Several theoretical proposals describe horizonless compact objects that can mimic black holes in their gravitational wave signatures; however, their spin-induced quadrupole moments (SIQMs) may reveal their distinct nature. Using the tight bounds on the SIQM of GW241011, we place constraints on the nature of its primary. Across exotic compact object models considered in this Letter, we find that rotating boson stars with quartic self-interactions cannot explain the nature of the primary, whereas models of sufficiently large compactness, C≳0.24, may still be viable contenders.
Infrared (IR) and Raman vibrational spectra of materials and surfaces can be rather complex and are often interpreted in combination with simulations based on the double-harmonic approximation. A variety of anharmonic spectral features (band shifts, combination bands, overtones, hot bands, resonances) affect the spectra both quantitatively and qualitatively. We introduce a general method for the efficient description of these anharmonic features-including Fermi and Darling-Dennison resonances-in IR and Raman spectra of materials from first principles. Nuclear quantum effects are explicitly taken into account, and phonon couplings are treated nonperturbatively within a new subspace iterative vibrational configuration interaction (SI-VCI) approach. We apply the SI-VCI method to solid thiourea and solid CO_{2} (dry ice): two molecular crystals with distinct characteristics. Thiourea is a hydrogen-containing system for which we identify a strong three-mode Fermi-like resonance SS:b+b^{'} between the fundamental of a symmetric stretching and the combination of two distinct bending modes of NH_{2} groups in the solid phase, which is not observed in the isolated gas-phase molecule. Our results, supported by group theoretical arguments, exclude the presence of bending overtones in the resonant mechanism. Dry ice exhibits four known resonances appearing in the form of dyads and triads (two in the IR spectrum and two in the Raman spectrum), which are also observed in the gas-phase isolated molecule. Our simulations predict an additional Fermi resonance in the IR spectrum of CO_{2} around 2000 cm^{-1} in the form of a dyad with a splitting δ≃150 cm^{-1}. We perform IR transmission experiments where the new resonant spectral feature is observed, assessing the predictiveness of the proposed theoretical approach.
The center of mass and helicity are two dynamic degrees of freedom of skyrmions. In this Letter, we study the current-driven skyrmion motion in frustrated d-wave altermagnets. Contrary to conventional wisdom, we find that the skyrmion helicity is not locked with the skyrmion Hall angle, but unidirectionally rotates with a global angular velocity proportional to the square of the current density. In addition, we find that the helicity rotation velocity is highly anisotropic, depending on the direction of current flows. We also observe helicity oscillation in the terahertz regime, where the nonlinear mixing between the fast and slow modes generates a comblike spectrum. Full atomistic spin dynamics simulations verify our theoretical predictions. Our results establish frustrated altermagnets as a promising platform for skyrmionics, terahertz technology, and magnon frequency comb.
