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  • Enhanced extracellular matrix remodeling due to embedded spheroid fluidization
    Embedding a collective of tumor cells, i.e. a tumor spheroid, in a fibrous environment, such as a collagen network, provides an essential in vitro platform to investigate the biophysical mechanisms of tumor invasion. To predict new mechanisms, we develop a three-dimensional computational model of an embedded spheroid using a vertex model, with cells represented as deformable polyhedrons, mechanically coupled to a fiber network via active linker springs. As the linker springs actively contract, the fiber network remodels. As we tune the rheology of the spheroid and the fiber network stiffness, we find that both factors affect the remodeling of the fiber network with fluid-like spheroids densifying and radially realigning the fiber network more on average than solid-like spheroids but only for a range of intermediate fiber network stiffnesses. Our predictions are supported by experimental studies comparing non-tumorigenic MCF10A spheroids and malignant MDA-MB-231 spheroids embedded in collagen networks. The spheroid rheology-dependent effects are the result of cellular motility generating spheroid shape fluctuations. These shape fluctuations lead to emergent feedback between the spheroid and the fiber network to further remodel the fiber network. This emergent feedback occurs only at intermediate fiber network stiffness since at low fiber network stiffness, the mechanical response of the coupled system is dominated by the spheroid and for high fiber network stiffness, the mechanical response is dominated by the fiber network. We are therefore able to quantify the regime of optimal spheroid-fiber network mechanical reciprocity. Our results uncover intricate morphological-mechanical interplay between an embedded spheroid and its surrounding fiber network with both spheroid contractile strength and spheroid shape fluctuations playing important roles in the pre-invasion stages of tumor invasion.

  • Photon-polarization-resolved linear Breit–Wheeler pair production in a laser-plasma system
    The linear Breit–Wheeler (LBW) process—the production of an electron–positron pair through the collision of two high-energy photons—can emerge as the dominant pair production mechanism in the ultraintense laser-plasma interaction for laser intensities below 1023 W cm−2. Here, we explore the role of γ photon polarization in LBW pair production for a 10 PW-class, linearly polarized laser interacting with a solid-density plasma. The motivation for this investigation lies in two main aspects: γ photons emitted via nonlinear Compton scattering are inherently linearly polarized, and the LBW process exhibits a distinct sensitivity to γ photon polarization. By leveraging particle-in-cell simulations that self-consistently incorporate photon-polarization-resolved LBW pair production, our results reveal that γ photon polarization leads to a 5% to 10% reduction in the total LBW positron yield. This suppression arises because the polarization directions of the colliding γ photons are primarily parallel, reducing the LBW cross section compared to the unpolarized case. The influence of γ photon polarization weakens as the laser intensity increases or the scale length of preplasmas at the front of the target increases.

  • Anderson localization: a disorder-induced quantum bound state
    Electrons at the Fermi energy may lose their ability to propagate to long distances in certain random media. We use Green functions and solve parquet equations for the non-local electron–hole vertex to describe the vanishing of diffusion in Anderson localization. It is caused by a diverging timescale responsible for forming a quantum bound state between the diffusing particle and the hole left behind. Divergence in this new timescale, proportional to the electrical polarizability, signals the Anderson localization transition. The critical behavior with this scale becomes symmetric on both sides of the transition. Consequently, the height of the peak of the dynamic conductivity in the metallic phase, the static diffusion constant, is not pushed to zero at the localization transition, but rather its width. Spatially localized quantum bound states cannot be described by the standard continuity and diffusion equations in the Hilbert space of Bloch waves with real wave vectors.

  • Quantum interference among vortex bound states in superconductors
    In a recent experiment (Hou et al 2025 Phys. Rev. X15 011027), a new type of necklace-like vortex bound state (VBS) was observed and attributed to disorder induced interference among different Caroli–de Gennes–Matricon (CdGM) states within one single vortex. In this work, we further investigate the possibilities of quantum interference among the CdGM states from different vortices in clean superconductors, which may become significant near the upper critical field. We find a series of interference patterns in the local density of states (LDOS) due to the overlap between spatially separated individual CdGM states. On a vortex lattice, the interference can also lead to a necklace-like LDOS, hence, providing an alternative and intrinsic mechanism to observe the novel necklace-like, or other spatially modulated VBS more generally, in experiments. These results can be understood quite well within an effective tight-binding model constructed from the individual CdGM states, and can be checked in future experiments.

  • Quantum correlations and spatial localization in trapped one-dimensional ultra-cold Bose–Bose–Bose mixtures
    We systematically investigate and illustrate the complete ground-state phase diagram for a one-dimensional, three-species mixture of a few repulsively interacting bosons trapped harmonically. To numerically obtain the solutions to the many-body Schrödinger equation, we employ the improved Exact Diagonalization method (Anh-Tai et al 2023 SciPost Phys.15 048), which is capable of treating strongly-correlated few-body systems from first principles in an efficiently truncated Hilbert space. We present our comprehensive results for all possible combinations of intra- and interspecies interactions in the extreme limits that are either the ideal limit (g = 0) or close to the hard-core limit ( ). These results show the emergence of unique ground-state properties related to correlations, coherence and spatial localization stemming from strongly repulsive interactions.