Communications Physics最新文献

In many multiferroics, rare-earth and transition-metal orders coexist. For analyzing their interaction and its consequences for the multiferroic state, the domain patterns and their spatial correlation give valuable insight. Unfortunately, this is often hampered by the lack of access to the domains of the rare-earth order. Here, we uncover such a domain pattern for the multiferroic Dy_0.7Tb_0.3FeO₃. Optical second harmonic generation reveals columnar Dy/Tb domains. The columns arrange perpendicular to the magnetically induced electric polarization. Hence, the antiferromagnetic rare-earth order forces the ferroelectric domains to form nominally charged domain walls. In turn, to reduce energy, the ferroelectric order causes a diminished rare-earth domain-wall density along the polarization direction. This interplay highlights the multiferroic character of the Dy_0.7Tb_0.3FeO₃ domain pattern and the important role of the rare-earth order. We position Dy_0.7Tb_0.3FeO₃ within the broader landscape of rare-earth multiferroics identifying three distinct scenarios for the role of rare-earth order.

Atomic nuclei serve as prime laboratories for investigations of complex quantum phenomena, where minor nucleon rearrangements cause significant structural changes. ¹⁹⁰Pb is the heaviest known neutron-deficient Pb isotope that can exhibit three distinct shapes: prolate, oblate, and spherical, with nearly degenerate excitation energies. Here we report on the combined results from three state-of-the-art measurements to directly observe these deformations in ¹⁹⁰Pb. Contrary to earlier interpretations, we associate the collective yrast band as predominantly oblate, while the non-yrast band with higher collectivity follows characteristics of more deformed, predominantly prolate bands. Direct measurement of the $E0\left(0_2^{+}\to 0_1^{+}\right)$ transition and γ-e ^- coincidence relations allowed us to locate and firmly assign the $0_2^{+}$ state in the level scheme and to discover a spherical $2_3^{+}$ state at 1281(1) keV with $B\left(E2;2_3^{+}\to 0_1^{+}\right)=1.2\left(3\right)$ W.u. These assignments are based purely on observed transition probabilities and monopole strength values, and do not rely on model calculations for their interpretation.

The study of quantum reference frames (QRFs) is motivated by the idea of taking into account the quantum properties of the reference frames used, explicitly or implicitly, in our description of physical systems. Like classical reference frames, QRFs can be used to define physical quantities relationally. Unlike their classical analogue, they relativise the notions of superposition and entanglement. Here, we explain this feature by examining how configurations or locations are identified across different branches in superposition. We show that, in the presence of symmetries, whether a system is in "the same" or "different" configurations across the branches depends on the choice of QRF. Hence, sameness and difference - and thus superposition and entanglement - lose their absolute meaning. We apply these ideas to the context of semi-classical spacetimes in superposition and use coincidences of four scalar fields to construct a comparison map between spacetime points in the different branches. This reveals that the localisation of an event is frame-dependent. We discuss the implications for indefinite causal order and the locality of interaction and conclude with a generalisation of Einstein's hole argument to the quantum context.

Understanding quantum tunneling in many-body systems is crucial for advancing quantum technologies and nanoscale device design. Despite extensive studies of quantum tunneling, the role of interactions in determining directional transport through asymmetric barriers in discrete quantum systems remains unclear. Here we show that noninteracting fermions exhibit symmetric tunneling probabilities regardless of barrier orientation, while inter-particle interactions break this symmetry and create pronounced asymmetric tunneling behavior. We explore the dependence of tunneling behavior on the initial spin configurations of two spin-1/2 fermions: spin-triplet states preserve tunneling symmetry, while spin-singlet states show strong asymmetry. We identify regimes where interactions mediate tunneling through under-barrier resonant trapping and enhance tunneling via many-body resonant tunneling - a phenomenon arising solely from inter-particle interactions and being fundamentally different from traditional single-particle resonant tunneling. Our results may be applied to the design of nanoscale devices with tailored transport properties, such as diodes and memristors.

Event cameras, as novel bio-inspired neuromorphic sensors, detect per-pixel brightness changes asynchronously. Despite their growing popularity in various applications, their potential in X-ray imaging remains largely unexplored. Synchrotron-based X-ray imaging plays a significant role in various fields of science, technology and medicine. However, time-resolved imaging still faces several challenges in achieving higher sampling rates and managing the substantial data volume. Here, we introduce an inline dual-camera setup, which leverages a high-speed CMOS camera and an event camera, aiming to temporally super-resolve the sampled frame data using sparse events. To process the data, frames and events are first aligned pixel-by-pixel using feature matching, and then used to train a deep-learning neural network. This network effectively integrates the two modalities to reconstruct the intermediate frames, achieving up to a 6-fold temporal upsampling. Our work demonstrates an event-guided temporal super-resolution approach in the X-ray imaging domain, which unlocks possibilities for future time-resolved experiments.

Many social interactions are group-based, yet their role in social polarization remains largely unexplored. To bridge this gap here we introduce a higher-order framework that takes into account both group interactions and homophily. We find that group interactions can strongly enhance polarization in sparse systems by limiting agents' exposure to dissenting views. Conversely, they can suppress polarization in fully connected societies, an effect that intensifies as the group size increases. Our results highlight that polarization depends not only on the homophily strength but also on the structure and microscopic arrangement of group interactions.