The sterile neutrino interpretation of the LSND and MiniBooNE neutrino anomalies is currently being tested at three liquid argon detectors: MicroBooNE, SBND, and ICARUS. It has been argued that a degeneracy between ${\nu }_{\mu }\to {\nu }_e$ and ${\nu }_e\to {\nu }_e$ oscillations significantly degrades their sensitivity to sterile neutrinos. Through an independent study, we show two methods to eliminate this concern. First, we resolve this degeneracy by including external constraints on ${\nu }_e$ disappearance from the PROSPECT reactor experiment. Second, by properly analyzing the full three-dimensional parameter space, we demonstrate that the stronger-than-sensitivity exclusion from MicroBooNE alone already covers the entire $2\sigma$ preferred regions of MiniBooNE at the level of $2-3\sigma$. We show that upcoming searches at SBND and ICARUS can improve on this beyond the $4\sigma$ level, thereby providing a rigorous test of short-baseline anomalies.

We demonstrate a class of Co and CoPc molecular Kondo boxes on the Au(111) surface through scanning tunneling microscopy experiments and first-principles calculations. The $\pi$-electron states of the CoPc molecule hybridize with the conduction electron states of the Au(111) substrate, imparting itinerantlike electron characteristics. Because of the high symmetry matching between the $d_{\pi }$ orbitals of Co adatoms and the $\pi$ orbitals of CoPc, the large orbital overlap predominates the formation of a Kondo singlet within the molecular complexes that prevail over the competition from the metal substrate, enabling them effectively as the molecular Kondo boxes. Furthermore, increasing the number of Co adatoms and modulating the overall symmetry of the molecular Kondo box can effectively tune the Kondo temperature $T_{\mathrm{K}}$.

We define the absolute Wilson loop winding and prove that it bounds the (integrated) quantum metric from below. This Wilson loop lower bound naturally reproduces the known Chern and Euler bounds of the integrated quantum metric and provides an explicit lower bound of the integrated quantum metric due to the time-reversal protected ${\mathbb{Z}}_2$ index, answering a hitherto open question. In general, the Wilson loop lower bound can be applied to any other topological invariants characterized by Wilson loop winding, such as the particle-hole ${\mathbb{Z}}_2$ index. As physical consequences of the ${\mathbb{Z}}_2$ bound, we show that the time-reversal ${\mathbb{Z}}_2$ index bounds superfluid weight and optical conductivity from below and bounds the direct gap of a band insulator from above.

Multistate ferroelectric polarization holds promise for realizing high-density nonvolatile memory devices, but so far is restricted to a few traditional ferroelectrics. Here, we show that nanoconfined two-dimensional (2D) ferroelectric ice can achieve phase-dependent multistate polarization through extensive classical and ab initio molecular dynamics simulations. An in-plane electric field is found to induce the reversible transition between a low-polarization $AA$-stacked hexagonal ice phase and an unprecedented high-polarization $AB$-stacked ice phase, resulting in a four-state ferroelectric switching pathway. The findings highlight the potential of 2D ice as a functional material for the development of multistate ferroelectric memory devices.

We investigate the quasiparticles of a single nodal ring semimetal ${\text{SrAs}}_3$ through axis-resolved magneto-optical measurements. We observe three types of Landau levels scaling as $ϵ\sim \sqrt{B}$, $ϵ\sim B^{2/3}$, and $ϵ\sim B$ that correspond to Dirac, semi-Dirac, and classical fermions, respectively. Through theoretical analysis, we identify the distinct origins of these three types of fermions present within the nodal ring. In particular, semi-Dirac fermions—a novel type of fermion that can give rise to a range of unique quantum phenomena—emerge from the end points of the nodal ring where the energy band disperses linearly along one direction and quadratically along the perpendicular direction, a feature not achievable in nodal point or line structures. The capacity of the nodal ring to simultaneously host multiple fermion types, including semi-Dirac fermions, establishes it as a valuable platform to expand the understanding of topological semimetals.

Building localized states with high quality factors in compact dynamic systems could enhance the performance of wave control devices such as elastic filters and high-precision sensing devices. Here, we report on the theoretical and experimental investigation of symmetry-protected bound states in the continuum (BICs) in a compressed metaplate. The proposed theory establishes a Bessel-zero-directed multipolarization design that enables precise modulation for the frequencies and modes of BICs. Experimental results reveal a critical threshold for symmetric protection, beyond which the polarization mode of BICs still exists despite leakage modes. The measured quality factor of BICs in the cylindrical-shelled metaplate rises to 720 via symmetry translation. The metaplate shows an enhanced performance over conventional defect and topological modes. This work opens a route toward compact elastic devices for applications in fields like on-chip communication, elastic wave filtering, and high-precision sensing within tight environments.

Sparse connectivity is a hallmark of the brain and a desired property of artificial neural networks. It promotes energy efficiency, simplifies training, and enhances the robustness of network function. Thus, a detailed understanding of how to achieve sparsity without jeopardizing network performance is beneficial for neuroscience, deep learning, and neuromorphic computing applications. We used an exactly solvable model of associative learning to evaluate the effects of various sparsity-inducing constraints on connectivity and function. We determine the optimal level of sparsity achieved by the ${\ell }_0$ norm constraint and find that nearly the same efficiency can be obtained by eliminating weak connections. We show that this method of achieving sparsity can be implemented online, making it compatible with neuroscience and machine learning applications.

We study the elementary problem of moving an active particle by a trap with minimum work input. We show analytically that (open-loop) optimal protocols are not affected by activity, but work fluctuations are always increased. For closed-loop protocols, which rely on initial measurements of the self-propulsion, the average work has a minimum for a finite persistence time. Using these insights, we derive an optimal periodic active information engine, which is found to have higher precision and information efficiency when operated with a run-and-tumble particle than for an active Ornstein-Uhlenbeck particle and, we argue, than for any other type of active particle.

We propose a two parameters extension of the flat $\mathrm{\Lambda }\mathrm{CDM}$ model to capture the impact of matter inhomogeneities on our cosmological inference. Non virialized but nonlinearly evolving overdense and underdense regions, whose abundance is quantified using the Press-Schechter formalism, are collectively described by two effective perfect fluids ${\rho }_{\mathrm{c}}$, ${\rho }_{\mathrm{v}}$ with nonvanishing equation of state parameters $w_{\mathrm{c},\mathrm{v}}\ne 0$. These fluids are coupled to the pressureless dust, akin to an interacting DM-DE scenario. The resulting phenomenology is very rich, and could potentially address a number of inconsistencies of the standard model, including a simultaneous resolution of the Hubble and ${\sigma }_8$ tensions. To assess the viability of the model, we set initial conditions compatible to the Planck 2018 best fit $\mathrm{\Lambda }\mathrm{CDM}$ cosmology and fit its additional parameters using SN Ia observations from DESY5, BAO distances from DESI DR2 and a sample of uncorrelated $f{\sigma }_8$ measurements. Our findings show that backreaction effects from the cosmic web could restore the concordance between early and late Universe cosmological probes.

Feebly interacting particles, such as sterile neutrinos, dark photons, and axions, can be abundantly produced in the proto-neutron star (PNS) formed in core-collapse supernovae (CCSNe). These particles can decay into photons or charged leptons, depositing energy outside the PNS. Strong bounds on new particles can thus be derived from the observed luminosity of CCSNe, with even tighter bounds obtained from low-energy SNe observations. For the first time we highlight that, at sufficiently large couplings, particle production outside the PNS must also be considered. Using the prototypical case of axions coupling to two photons, we show that at large couplings the energy transfer from PNS to its surroundings is diffusive rather than ballistic, substantially reducing the deposited energy. Our findings have implications for the parameter space of particles probed in beam dump experiments and for dark matter models involving a sub-GeV mediator.

We have performed careful measurements of nonlinear transverse conductivity (NLTC) at zero field in the intermetallic compound HoAgGe with two distinct magnetic toroidal (MT) structures. Below 7 K (MT1 phase), the NLTC signal becomes observable and significantly increases with decreasing temperature, whereas between 7 and 11.6 K (MT2 phase), it remains nearly zero. However, this result is incompatible with the previous research, which assigned the former and latter MT phases as antiferro- and ferro-MT structures, respectively. This discrepancy stems from an inappropriate assignment of MT structures in prior studies. Our analysis, based on multipole theory, redefines the MT1 and MT2 phases as ferri- and antiferro-MT structures, respectively, providing a coherent framework to explain the observed NLTC in HoAgGe. These findings not only establish NLTC as a robust diagnostic tool for identifying MT metals but also highlight its potential for exploring phenomena driven by the antiferroic interactions of MT dipoles.

We report direct spectroscopic evidence of correlation-driven Mott states in layered ${\mathrm{Nb}}_3{\text{Cl}}_8$ through combining scanning tunneling microscopy (STM) and dynamical mean-field theory. The Hubbard bands persist down to monolayer, providing the definitive evidence for the Mottness in ${\mathrm{Nb}}_3{\text{Cl}}_8$. While the size of the Mott gap remains almost constant across all layers, a striking layer-parity-dependent oscillation emerges in the local density of states (LDOS) between even ($n=2$, 4, 6) and odd layers ($n=1$, 3, 5), which arises from the dimerization and correlation modulation of the obstructed atomic states, respectively. Our conclusions are supported by a critical technical advance in atomic-scale LDOS mapping for highly insulating systems. This Letter provides the definitive experimental verification of correlation-driven Mott ground states in ${\mathrm{Nb}}_3{\text{Cl}}_8$, while establishing a general protocol for investigating the interplay of electronic correlation and interlayer coupling in layered insulators by using a low-temperature STM technique.

Hyperbolic lattices present a unique opportunity to venture beyond the conventional paradigm of crystalline many-body physics and explore correlated phenomena in negatively curved space. As a theoretical benchmark for such investigations, we extend Kitaev’s spin-$1/2$ honeycomb model to hyperbolic lattices and exploit their non-Euclidean space-group symmetries to solve the model exactly. We elucidate the ground-state phase diagram on the $\{8,3\}$ lattice and find a gapped ${\mathbb{Z}}_2$ spin liquid with Abelian anyons, a gapped chiral spin liquid with non-Abelian anyons and chiral edge states, and a Majorana metal whose finite low-energy density of states is dominated by non-Abelian Bloch states.

The far-from-equilibrium dynamics of certain interacting quantum systems still defy precise understanding. One example is the so-called quantum many-body scars (QMBSs), where a set of energy eigenstates evade thermalization to give rise to long-lived oscillations. Despite the success of viewing scars from the perspectives of symmetry, commutant algebra, and quasiparticles, it remains a challenge to elucidate the mechanism underlying all QMBS and to distinguish them from other forms of ergodicity breaking. In this work, we introduce an alternative route to detect and diagnose QMBS based on Fisher zeros, i.e., the patterns of zeros of the analytically continued partition function $Z$ on the complex $\beta$ (inverse temperature) plane. For systems with scars, a continuous line of Fisher zeros will appear off the imaginary $\beta$ axis and extend upward, separating the $\beta$ plane into regions with distinctive thermalization behaviors. This conjecture is motivated from interpreting the complex $Z$ as the return amplitude of the thermofield double state, and it is validated by analyzing two models with QMBS, the $\overline{P}X\overline{P}$ model and the Ising chain in external fields. These models also illustrate the key difference between QMBS and strong ergodicity breaking including their distinctive renormalization group flows on the complex $\beta$ plane. This “statistical mechanics” approach places QMBS within the same framework of thermal and dynamical phase transitions. It has the advantage of spotting scars without exhaustively examining each individual quantum state.

We analyze the impact of non-Markovian classical noise on single-qubit randomized benchmarking experiments, in a manner that explicitly models the realization of each gate via realistic finite-duration pulses. Our new framework exploits the random nature of each gate sequence to derive expressions for the full survival probability decay curve which are nonperturbative in the noise strength. In the presence of non-Markovian noise, our approach shows that the decay curve can exhibit a strong dependence on the gate implementation method, with regimes of both exponential and power law decays. We discuss how these effects can complicate the interpretation of a randomized benchmarking experiment, but also how to leverage them to probe non-Markovianity.

The color code has been invaluable for the development of the theory of fault-tolerant logic gates using transversal rotations. Three-dimensional examples of the color code have shown us how its structure, specifically the intersection of the supports of logical operators, can give rise to non-Clifford $T$ and $CCZ$ gates. Here we present a color code with a logical control-$S$ gate that is accomplished with transversal $T$ and $T^{†}$ rotations on its physical qubits.