Abstract We study a non-Hermitian Ising chain with a power-law quasiperiodic field h j = h cos p (2 παj + ϕ ), where the positive integer p controls the power of the modulation. The model admits an exact site-factorized similarity transformation that maps the quasi-Hermitian regime onto a real quasiperiodic Ising chain. We derive the exact zero-mode edge-localization boundary and show that the critical field on the quasi-Hermitian branch scales as 2 p , while the associated localization-length exponent remains unity for all p . At the boundary, the variance of the logarithmic coupling fluctuations is enhanced exactly by a factor of p 2 . In the quasi-Hermitian regime, the factorized similarity transformation shows that the spatial biorthogonal entanglement spectrum is identical to that of the Hermitian counterpart. The half-chain entanglement entropy exhibits approximately logarithmic growth over the accessible sizes, with a p -dependent finite-size slope. We finally discuss a possible realization using state-selective loss and conditional no-jump dynamics.
Abstract We report an ultracold electron beam with Kelvin-level transverse temperature generated from a cold atom electron source by two-color near-threshold photoionization of 87 Rb atoms in a magneto-optical trap. A novel self-referenced scheme was employed to precisely determine its transverse temperature. In this scheme, a 3×3 beam array was generated to provide an in situ reference, allowing the transfer-matrix element to be determined directly from the measured grid pattern. The transverse momentum spread of the central beam at the source plane is then retrieved, yielding a transverse temperature of T = 2.0 ± 1.0 K, with the corresponding intrinsic coherence length of L c = 21.1 ±5.0 nm and a relative coherence length of C ⊥ = (1.3 ± 0.4) × 10 -3 . The new scheme significantly suppresses the influence of residual magnetic fields, electric field inhomogeneities and electron-optical aberrations. A non-monotonic dependence of the transverse temperature on excess energy was observed and was qualitatively explained by the simulation using a polarization-dependent single-atom Coulomb-Stark trajectory model.
Abstract The Nielsen–Ninomiya theorem mandates that the net chiral charge of topological nodes in a crystal’s Brillouin zone must vanish, requiring them to appear in pairs. While realizing the absolute minimum of a single pair of topological nodes has been achieved for Weyl semimetals, hosting the minimal configuration of chiral charge-two (| C | = 2) triple-degenerate points (C-2 TPs) in a realistic electronic material remains an open challenge. By combining little-group constraints with both possible two-node orbit structures across all 1651 magnetic space groups (MSGs), we identify 21 MSGs without spin–orbit coupling (SOC) and 3 MSGs with SOC that are compatible with an isolated single pair of C-2 TPs. Guided by these symmetry criteria, we predict that the cubic boron allotrope P 23-B 36 acts as a premier electronic platform for this exotic phase. Owing to the negligible SOC of light boron atoms, the system behaves as a spinless semimetal, where the three crossing bands form exactly two symmetry-enforced C-2 TPs at the high-symmetry points Γ and R with chiralities C = +2 and C = 2, respectively. First-principles calculations reveal maximally extended double Fermi arcs on both the (001) and (110) surfaces, providing a distinct spectroscopic fingerprint for experimental detection. Our work establishes a rigorous symmetry-guided design framework for minimal multifold semimetals and identifies an elemental platform for exploring their intrinsic quantum transport phenomena.
The ultrafast dissociation of hydrogen-bonded clusters offers a fundamental route to studying energy relaxation and intermolecular proton transfer.Here,we investigate the three-body fragmentation of the HCl dimer following strong-field ionization into tricationic states.Angle-resolved kinetic energy measurements reveal distinct breakup mechanisms:a direct Coulomb explosion and the two pathways mediated by intermolecular charge transfer and proton transfer.The kinetic energy distributions of the Cl+and HCl+fragments evolve from a single peak to a double-peak structure as the relative emission angle increases.Ab initio calculations of the tricationic potential energy surface indicate that this splitting arises from competing charge-transfer and proton-transfer driven dissociation pathways.These results illustrate how ultrafast charge redistribution and proton motion govern the strong-field dissociation dynamics of a prototypical hydrogen-bonded cluster.
M & ouml;ssbauer nuclei with quadrupole-split levels provide a versatile platform for exploring coherent x-ray light-matter interactions. We theoretically study ensembles of 57Fe nuclei embedded in thin-film x-ray cavities, explicitly accounting for different orientations of the electric field gradient. By mapping isotropic electric field gradient distributions to an effective equal-weight two-transition model, we derive analytical expressions for the time-dependent reflectivity and reveal the emergence of cavity-mediated quantum beats. The oscillation frequency and temporal profile of these beats can be tuned via the cavity-induced coherent coupling, offering a flexible approach to control collective nuclear dynamics and manipulate nuclear coherence in the x-ray regime.
