AAPPS Bulletin最新文献

By using the exact Bethe wavefunctions of the one-dimensional Hubbard model with N spin-up fermions and one spin-down impurity, we derive an analytic expression of the impurity form factor, in the form of a determinant of a ((N+1)) by ((N+1)) matrix. This analytic expression enables us to exactly calculate spectral properties of one-dimensional Fermi polarons in lattices, when the masses of the impurity particle and the Fermi bath are equal. We present the impurity spectral function as functions of the on-site interaction strength and the filling factor of the Fermi bath, and discuss the origin of Fermi singularities in the spectral function at small momentum and the emergence of polaron quasiparticles at large momentum near the boundary of Brillouin zone. Our analytic expression of the impurity form factors pave the way to exploring the intriguing dynamics of a particle interacting with a Fermi bath. Our exact predictions on the impurity spectral function could be directly examined in cold-atom laboratories by using the radio-frequency spectroscopy and Ramsey spectroscopy.

Dark states, which are incapable of absorbing and emitting light, have been widely applied in multiple disciplines of physics. However, the existence of dark states relies on certain strict constraints on the system. For instance, in the fundamental (Lambda) system, a perturbation breaking the degeneracy between two energy levels may destroy the destructive interference and demolish the dark state. Here, we show that non-Hermiticity can be exploited as a constructive means to restore a dark state. By compensating for the undesired perturbations, non-Hermiticity produces unidirectional couplings such that the dark state remains decoupled from the rest of the system. Implementing this scheme in many-body systems, flat bands and edge states can be recovered by losses and gains. Further taking into account interactions, a range of novel quantum phases could arise in such non-Hermitian systems.

Particle accelerators, originally developed to address fundamental questions about the universe, have become essential to various scientific disciplines. The broad adoption of accelerators was enabled by substantial advancements in beam manipulation techniques, which encompass methods for generating and controlling particle beams to optimize them for specific applications. Most of these manipulations rely on controlling the beam’s correlation in its phase space. While linear control and the correction of low-order nonlinearities have propelled particle accelerators to their current state, the exploration of more advanced control methods may provide new opportunities to achieve unprecedented beam qualities and conditions. Consequently, there is an increasing demand for control over higher-order nonlinearities. A recently developed method utilizing transverse wigglers shows potential in addressing such demands. Active research is also ongoing on diverse applications of the transverse wiggler-based method in various accelerator fields. This paper discusses methods for controlling highly nonlinear correlations and their applications.

I briefly review the canonical vorticity theoretical framework and its applications in collisionless, magnetized plasma physics. The canonical vorticity is a weighted sum of the fluid vorticity and the magnetic field and is equal to the curl of the canonical momentum. By taking this variable as the primary variable instead of the magnetic field, various phenomena that require non-MHD effect in their scrutiny can be simplified. Two examples are given, namely magnetic reconnection and magnetogenesis, and exactly how the canonical vorticity framework simplifies their analyses is described. Suggestions for future work are also delineated.

We study the macroscopic quantum tunnelling of an interacting Bose-Einstein condensate in a cubic-plus-quadratic well that was approximately realized in recent experiment. We utilise the Gross-Pitaevskii equation and Wentzel-Kramers-Brillouin (WKB) method to investigate the effect of the inter-atomic interactions on the tunnelling rate of a quasi-bound condensate. We find that the existence of repulsive interaction enhances the quantum tunnelling of a trapped Bose-Einstein condensate.

In this work, we propose a geometric non-linear current response induced by magnetic resonance in magnetic Weyl semimetals. This phenomenon is in analog to the quantized circular photogalvanic effect (de Juan et al., Nat. Commun. 8:15995, 2017) previously proposed for Weyl semimetal phases of chiral crystals. However, the non-linear current response in our case can occur in magnetic Weyl semimetals where time-reversal symmetry, instead of inversion symmetry, is broken. The occurrence of this phenomenon relies on the special coupling between Weyl electrons and magnetic fluctuations induced by magnetic resonance. To further support our analytical solution, we perform numerical studies on a model Hamiltonian describing the Weyl semimetal phase in a topological insulator system with ferromagnetism.

This article highlights the significance of level lifetime measurements in nuclear structure studies that principally center on probing the myriad excitation phenomena exhibited by nuclei through evolving regimes of excitations in energy, angular momentum, and isospin. The same has been illustrated through discussions on some of the measurements undertaken using the Indian National Gamma Array (INGA) set up at the BARC-TIFR Pelletron LINAC Facility (PLF) in TIFR, Mumbai. The diverse physics that could be addressed in such endeavors provides the impetus to work towards developing better facilities for spectroscopic pursuits.