Papers

Subterranean and mound-building termites excavate, transport, and build within the same granular substrate that later regulates how they sense, move, and deposit material. From antennal-scale contacts through body-scale traffic to meter-scale architecture, this review synthesizes three linked problems: how workers sense local geometry and physical cues during search and excavation; how traffic moves through narrow, evolving conduits; and how excavation and deposition remodel the substrate that guides later behavior. Across these length scales, noisy local interactions couple sensing, transport, and construction through a shared material medium, leading to emergent order at the colony scale. We emphasize what is established experimentally, where evidence remains sparse or limited to a few model systems, and how emerging imaging, tracking, and modeling tools are making these feedbacks quantitatively accessible. We use this synthesis to motivate a quantitative physics-of-life framework for termite colonies that continually rewrite the medium through which they sense, move, and build.

We consider the typical tight - binding model of Dirac semimetal in the presence of both magnetic and electric fields. The electric conductivity reveals dependence on magnetic field. We calculate this dependence in the limit of strong magnetic field, when the given model is described effectively by the one - dimensional SSH model because the dynamics in the plane orthogonal to magnetic field is reduced to that of the lowest Landau level (LLL). Considering the small temperature limit we take into account dissipation due to scattering on impurities. The corresponding dissipation rate is calculated explicitly. The obtained results confirm that the source of the magnetoconductivity in this system is chiral magnetic effect.

Photogenerated polarons are fundamental to the photophysics of transition metal oxide semiconductors. It is therefore imperative to understand the mechanisms by which polarons form upon photoexcitation of transition metal oxides to realize their potential in photoapplications. Hematite ({\alpha}-Fe2O3) is known to form photoexcited small polarons, which limit its performance as a photoelectrocatalyst for water oxidation. Here, we report a systematic comparison of the electronic, optical and vibrational properties of hematite to those other metal oxides in the corundum crystal family that elucidates the impact of d-orbital radius on carrier-phonon coupling. Three corundum metal oxides are analyzed: {\alpha}-Al2O3 (no d-electrons), {\alpha}-Fe2O3 (3d), and {\alpha}-Rh2O3 (4d) with a combined approach of resonance Raman spectroscopy, thermal difference optical spectroscopy, and computational modeling of electronic and vibrational states. We find that the Raman spectrum of {\alpha}-Al2O3 does not change as the Raman excitation is varied across the visible region, as there is no optical absorption. In contrast, both {\alpha}-Fe2O3 and {\alpha}-Rh2O3 exhibit strong coupling of phonons to optical transitions at the onset of absorption, which is evidence of excitation into a polaronic state. Closely comparing the optical polaronic properties of {\alpha}-Fe2O3 and {\alpha}-Rh2O3, we establish that increased lattice covalency in {\alpha}-Rh2O3 arising from the increased radial extension of the 4d orbitals influences which phonon modes mediate photogenerated polaron formation.

A soft thin elastic disk spinning in a viscous fluid experiences centrifugal tension generated by rotation together with viscous shear generated by the surrounding flow. While the former stabilizes the flat state, the latter can destabilize it. We combine the linearized Föppl-von Kármán equations for a rotating elastic disk with the shear stresses arising from the classical von Kármán swirling flow to derive an elastohydrodynamic stability problem. Linear stability analysis identifies the onset of buckling in terms of two dimensionless control parameters measuring centrifugal stiffening and fluid-induced shear. Above threshold the disk buckles into azimuthally periodic saddle-like modes whose wavenumber increases with increasing rotational tension. The buckled configuration also supports retrograde traveling waves that rotate more slowly than the material frame. These results identify a simple mechanism whereby fluid shear destabilizes rotating elastic structures.

Photoemission is an escape problem, yet first-principles calculations usually trap the electron in a periodic box. We present a parameter-free ab initio framework that removes this artificial boundary by constructing open scattering states for semi-infinite crystal-vacuum interfaces from Wannier Hamiltonians and Green-function embedding. The method gives continuum-normalized time-reversed LEED final states with microscopic quasiparticle attenuation. For Ag(111), it predicts absolute quantum efficiency, vectorial photoemission, and mean transverse energy on the experimental scale.

Entangling distant spins via a shared magnonic bus typically faces a tradeoff: stronger spin-magnon coupling increases the entanglement fidelity, but also the spin decay rate. We propose a protocol that breaks this tradeoff. The magnons couple only to a transition outside the computational basis, in which the Bell state is created. Our protocol is probabilistic, and weak coupling reduces the success probability but not the fidelity. We analyze a setup where the spins are two nitrogen-vacancy (NV) centers near a magnetic wire. In the absence of NV dephasing, the protocol reaches unit fidelity with a maximally entangled state, for arbitrarily weak coupling. In our simulations via the Monte-Carlo wavefunction approach, the NV-magnon coupling is taken to be one-third of the magnon linewidth. Considering finite NV dephasing, we predict a fidelity of >0.99 for a state-of-the-art rate, and an optimal fidelity of 0.91 for a moderate rate, both at 0.6% success probability.

Hydrogen Desorption Lithography on Si(100) demonstrates the ability of the Scanning Tunneling Microscope (STM) to create functional atomic-scale structures and devices. The dehydrogenation of adsorbed molecules represents a potential complementary technique that has received little attention. For example, formation of C$_{2}$ could introduce local strain or act as centers for subsequent reactions and would inform positionally controlled mechanosynthesis, an approach with vast potential in surface patterning and functionalization. Here, we studied the electron-induced dehydrogenation of acetylene and ethylene on Si(100) at 4 K using STM. Excitation of acetylene at +3.2 V and above induces configurational switching, including to a new sublayer-bonded geometry previously predicted to be an adsorption precursor, as well as migration and desorption. Excitation also induces dehydrogenation to C$_{2}$. Switching between three observed C$_{2}$ configurations can be induced by excitation at +4.2 V and above. Simulations using density functional theory reproduced the experimental images based on choice of functional, dimer-buckling averaging, and inclusion of diffuse basis functions. In addition, dehydrogenation could be induced using field-emitted electrons on a scale ranging from a single molecule to a radius of >10 nm. These observations highlight the potential of carbon dehydrogenation as an additional tool in Atomically Precise Fabrication (APF).

Network diffusion underlies many transport phenomena, with Laplacian modes setting how information spreads and relaxes. In physical networks, however, connectivity alone is not enough: node volumes introduce local dwell times that regulate how flow is stored before being propagated. Here we show that physical heterogeneity reshapes topology-driven localization, with the degree-volume ratio emerging as the relevant disorder parameter. We solve an analytical model in which ratio detuning qualitatively reorganizes the Laplacian spectrum, and demonstrate in empirical networks how degree-volume correlations shift extremal eigenmodes away from the nodes selected by topology alone. Our results reveal a general feature-rich-driven mechanism for localization control, showing that physicality non-trivially reshapes the disorder landscape governing network dynamics.

$p$-wave magnets exhibit odd-parity spin polarization in momentum space, with spin splitting that reverses under $\vec{k}\rightarrow -\vec{k}$, while preserving zero net magnetization. Here we show that, in odd-parity magnets with spin-orbit coupling, elliptically polarized light generates a momentum-independent spin-dependent term that dynamically switches a zero-net-magnetization $p$-wave state into a finite spin-polarized state. The Floquet-engineered bands also acquire a nonzero Chern number whose sign is controlled by the light polarization. For $f$-wave magnets, circularly polarized light induces a net out-of-plane magnetization, offering a direct experimental signature. Our results establish light as an efficient means of controlling magnetic states, with potential applications in spintronics and quantum information.

Quantum resonance arising whenever the ratio of the intrinsic system frequency to the driving frequency becomes a rational number has been demonstrated to generate super-linear entanglement, enhance transport, quantum metrology performance and communication. Here, we demonstrate that quantum resonance can also serve as a powerful resource for quantum batteries. We model the batteries as free rotors charged via a kicked protocol. When the individual batteries are at resonance, we show both analytically and numerically that charging power increases linearly with time while efficiency (defined as the fraction of stored energy that can be extracted) remains near unity despite strong entanglement generation. Furthermore, we demonstrate that this enhanced performance persists at higher-order resonances. Demonstrating the universality of this mechanism, we show that similar enhancements arise in the interacting kicked top model, and briefly note the feasibility of its experimental realization. In a broader context, resonant charging holds significant implications for energy storage, quantum computational resources, and quantum thermodynamics.

The recently observed signatures of superconductivity proximate to a fractional quantum anomalous Hall (FQAH) state in a twisted MoTe$_2$ bilayer has revitalized interest in quantum phases of matter induced by anyon dynamics. Here we show how a panoply of anyon-driven phases associated with doping the lattice ${\nu=2/3}$ FQAH state can be realized as competing instabilities of a Fermi surface of charge-$e/3$ “quarks” coupled to a $\mathrm{SU}(3)_{-1}$ Chern-Simons gauge field, which is dual to the more conventional $\mathrm{U}(1)_3$ Chern-Simons-Ginzburg-Landau theory of quasiholes. For example, a range of electronic superconductors emerge from color superconductivity, under which the Fermi surface experiences a pairing instability mediated by gauge fluctuations. These include SC$\star$ phases – where superconductivity coexists with topological order – as well as topological superconductors displaying half-integer chiral central charges when the quarks are weakly paired. One example is a $p+ip$ “color-valley-locked” superconductor, a topological analogue of the color superconductor familiar in quantum chromodynamics. On the other hand, both superconducting and non-Fermi liquid phases can emerge when the quarks form an itinerant ferromagnet, polarizing the Fermi surface to a particular combination of colors. Finally, our framework naturally accommodates the possibility of anyonic bound state formation, allowing access to phases induced by doping anyons of charge $2e/3$ as opposed to $e/3$ within the same model. Our work unifies many earlier proposed anyonic phases as instabilities of a single parent quark metal phase, distilling their emergence into a competition between superconductivity and itinerant color ferromagnetism.

Inspired by the progress on the study of exciton physics in atomically thin transition metal dichalcogenide (TMD) semiconductors, we investigate the formation of analogs of excitons in cold atomic systems. To this end, we consider single-component fermions comprised of ultracold ground-state molecules or dipolar atoms in a hexagonal optical lattice. An energy offset between triangular sublattices opens up a band gap with degeneracies at the K/K' points as in TMDs. We predict the existence of cold atomic excitons and show that cold atoms allow us to study excitons from the weak-coupling regime, where effective mass models apply, to the strong-interaction regime, described by flat-band models. We demonstrate how these excitons can be observed using lattice modulation spectroscopy, and how their wave functions can be mapped out using quantum gas microscopy. Firmly establishing the idea of quantum simulation of semiconductor physics, this work lays the foundation for simulating complex electronic states such as trions, polarons and excitonic insulators.

We obtain integer and fractional quantum Hall crystals as ground states of a two-dimensional electron system subject to a strong perpendicular magnetic field and a periodic potential. For certain fractional states, we show that the Hall crystal can constitute an anyon crystal, with a periodic ordering of well-defined anyons. We find that the latter states can be stabilized at odd denominator Landau level filling fractions when Landau level mixing is sufficiently weak, and near half-filling of the underlying lattice. These phases are obtained from a mean-field analysis of an effective lattice model of bosons attached to an odd number of flux quanta, which transmutes their statistics to that of electrons. In boson coordinates, the Hall crystal is a supersolid: a superfluid with charge order. Under strong interactions, vortex-anti-vortex pairs spontaneously nucleate in the supersolid, realizing a crystalline state of anyons.

Mott physics in topological bands has recently attracted considerable attention, particularly in the context of twisted bilayer graphene (TBG). However, the essential ingredients for stabilizing this physics remain unclear. Here, we demonstrate a quantum Mott semimetal phase as the ground state within a one-dimensional spinful Hubbard model featuring only one orbital per unit cell, protected by inversion and particle-hole symmetries. We start from a two-orbital model where a localized $f$ orbital on the A sublattice hybridizes with a delocalized $c$ orbital on the B sublattice. Projecting the $f$-orbital Hubbard $U$ onto the active flat band yields a lattice model with Wannier orbitals centered on the B sublattice. Similar to TBG, a momentum-space scale $k_*$ emerges, setting the interaction range in the projected model to $1/k_*$. While the ground state is ferromagnetic with only the Hubbard $U$, introducing an inter-site antiferromagnetic spin coupling $J$ stabilizes a Mott semimetal$^*$ phase with a central charge $c=3$. Using exact diagonalization (ED) and density matrix renormalization group (DMRG) methods, we show that this phase hosts a spinful Dirac fermion coexisting with a neutral spin mode – analogous to the fractionalized Fermi liquid (FL$^*$) phase in higher dimensions. Furthermore, breaking particle-hole (PH) symmetry via dispersion transforms the Mott semimetal into a Mott insulator, which is separated from a distinct Mott insulating phase by a continuous transition with a polarization jump of $1/2$. Our work provides the first unbiased evidence of a Mott semimetal ground state and demonstrates that this 1D model captures some essential aspects of TBG physics, despite lacking a Wannier obstruction.

MgB$_2$, a phonon-mediated superconductor with record-high critical temperature $T_c\simeq 39$ K, is revisited to obtain a comprehensive theory of electrons, phonons, and their coupling with minimal ab initio input. We construct compact analytic models for the electronic structure, phonons, and electron-phonon coupling (EPC) of MgB$_2$. We show that strong in-plane B $sp^2$ bonding realizes an obstructed band structure whose natural description is a bond-centered kagome lattice, yielding small quasi-2D $\sigma$-band Fermi-surface cylinders and pronounced quantum-geometric effects. The phonon spectrum is found to closely track that of a graphene-like boron layer, but the heavy intercalated Mg atoms dominate the three acoustic branches and rigidly lift the boron modes into the optical sector, while the in-plane B-B bond-stretching mode exhibits a pronounced softening along $\Gamma$-A. By symmetry, this $\Gamma$-point bond-stretching mode is the only $\Gamma$ phonon that can couple to the $\sigma$ Fermi surface, explaining its dominant contribution to the EPC. Upon electron doping toward the doubly degenerate band edge of the $\sigma$ sheets, we find that a reduced density of states competes with enhanced EPC matrix elements. At light electron doping, ab initio calculations show that the EPC enhancement dominates, leading to an increase in $T_c$ (within the clean doping limit without disorder effects). Using the Gaussian approximation for the EPC tensor, we further show that this enhancement is overwhelmingly quantum geometric in origin, arising from a geometric EPC contribution of the small $\sigma$ Fermi surface peaked at $\Gamma$. Overall, our results provide a transparent, symmetry-based account of superconductivity in MgB$_2$ and suggest that quantum-geometric effects can be essential for shaping doping trends in phonon-mediated superconductors.

Markov state models (MSMs) have become ubiquitous tools for analyzing molecular dynamics (MD) simulations because of their simple, powerful premise: although complete MD sampling may be impossible, the MSM can "stitch together" transition probabilities derived from local sampling to provide a global picture of kinetics and mechanisms. In the standard MSM framework, the available MD data is organized into a single transition matrix, which is then used to estimate all observables at a lag time chosen so the coarse-grained dynamics are approximately Markovian. This approach leads to avoidable model bias and motivates long lag times that obscure short-timescale processes of interest. In contrast, this paper shows how to obtain unbiased coarse-grained observables at any fixed lag time and for any fixed coarse-graining in the limit of infinite, properly weighted data. The central idea is to replace the single-matrix framework with two transition matrices – one representing equilibrium dynamics and another representing source-sink recycling dynamics – and use the correct matrix or matrices to estimate the matched dynamical observables.

Natural and engineered classical systems are replete with examples of synchronization, understood as the adjustment of rhythms of physical systems. Such synchronization is at the heart of the stability of several classical technologies, such as mechanical bridges and electrical networks. Given the advent of quantum simulation and computation technologies, it is natural to study a quantum analogue of synchronization and explore novel applications. This review surveys synchronization in few and many-body quantum systems, measures that quantify them, and their applications to quantum technologies.

Misfit layered compounds (MLCs) offer a unique bulk platform for realizing exotic quantum states typically associated with two-dimensional transition-metal dichalcogenides (TMDs), most notably Ising-protected superconductivity. Yet a theoretical description capturing their electronic structure beyond the simplistic picture of electronically isolated TMD layers has been lacking. Here, we develop a unified tight-binding model for metal dichalcogenide-based MLCs, parameterized by extensive density-functional theory (DFT) calculations across multiple structural configurations and chemical compositions. We show that the intervening tetragonal layers play an active role beyond charge reservoirs: they mediate a significant interlayer spin-orbit coupling entirely absent in the standard rigid-band picture. This emergent interlayer spin-orbit coupling is essential for reproducing the DFT band structure of bulk MLCs and, when incorporated into Bogoliubov–de Gennes calculations, provides a microscopic mechanism for the Ising protection of superconductivity by strongly enhancing the in-plane critical field. Our framework establishes MLCs as a distinct class of three-dimensional materials with intrinsically coupled layers and emergent spin-orbit phenomena.

Momentum-dependent nonrelativistic spin splitting provides a symmetry fingerprint of collinear magnets and can govern unconventional electronic, magnonic, and transport phenomena. Whereas even-parity $s$-, $d$-, $g$-, and $i$-wave splittings in collinear magnets have been extensively studied, odd-parity counterparts remain unexplored beyond the $p$-wave and $f$-wave classes. Here, using group theory, we establish the complete classification of odd-parity spin splitting in collinear magnets. We show that, in addition to the $p$-wave and $f$-wave forms, $h$- and $k$-wave splittings with $\ell=5$ and $7$ are allowed, while $m$-wave splitting with $\ell=9$ constitutes the upper bound. We derive a complete mapping from crystallographic point-group irreducible representations to the lowest-order odd-parity basis functions and formulate the coupling rule between a symmetry-breaking axial field and the parent Néel order that selects the induced odd-parity class. We further construct minimal lattice models that realize $h$-, $k$-, and $m$-wave splitting. Guided by this classification, we screen the MAGNDATA database and show that circularly polarized light can drive the $\mathcal{PT}$-symmetric antiferromagnets Fe$_2$TeO$_6$ and MgFe$_6$Ge$_6$ into $h$-wave and $k$-wave phases, respectively, exhibiting the hallmark spin splittings in both electronic bands and magnon spectra. Symmetry analysis and Berry-curvature calculations show that collinear odd-parity magnets of both $h$- and $k$-wave allow an anomalous Hall response, whereas the $m$-wave class forbids it. Together, these results complete the partial-wave hierarchy of odd-parity spin splitting in collinear magnets and establish symmetry criteria for anomalous transport in the high-partial-wave classes.

Characterizing phase transitions between correlated electronic phases, extracting their critical exponents, and identifying their universality class are of central interest in many-body physics. Here, we propose and demonstrate that photon correlation spectroscopy can be used to gain insight into the nature of critical electronic density fluctuations. We study a semiconductor moiré material consisting of two MoSe2 layers separated by a monolayer h-BN spacer and measure interlayer electron dynamics via the second-order correlation function of the scattered photons. The correlated transfer of large numbers of electrons between the layers at the onset of an Ising-type layer pseudo-spin phase transition leads to photon bunching in light scattered by the exciton resonance of one layer. Our measurements pave the way for using photon correlations as a method to access dynamical exponents associated with electronic phase transitions.

We propose a mechanism for fast and efficient quantum transport through disordered networks with variable on-site energies, inspired by photosynthetic complexes. The mechanism relies on an interplay between inter-site couplings of the network and driving by external vibrations. Two design principles are shown to ensure close-to-perfect transport despite the disorder, namely a reflection symmetry in Floquet-Hilbert space and the existence of a dominant doublet or triplet of Floquet states.

We propose a class of topological surface bands in three-dimensional topological crystalline insulators that have symmetry-protected cubic-order band touching. Within the symmetry constraint, the band dispersion can continuously vary between cubic dispersion, moat band and multi-mini-valley structure with van Hove singularities by adjusting particle-hole asymmetry and anisotropy. Thus, there is a family of tunable density-of-state singularities ranging from power-law to logarithmic divergences. This offrs a versatile platform for engineering strongly correlated phases of matter in topological surface states. We provide an example realization in a prism-lattice tight-binding model of angular-momentum-3/2 electrons.

We present a formally exact variational scheme for the overdamped Brownian dynamics of pairwise interacting many-body systems in general spatiotemporal nonequilibrium. A joint free power minimization principle determines instantaneously the one-body current and the global interparticle distance flux. The intrinsic free power functional splits into entropic and energetic rates, where the latter are treated explicitly. The adiabatic contribution to the entropy rate is the time derivative of the equilibrium entropy metadensity functional. Genuine nonequilibrium effects originate from a universal entropy superpower functional. Two continuity equations close the dynamical description.

We develop a theoretical framework based on the Dynamical Projective Operatorial Approach (DPOA) to study the time- and angle-resolved photoemission spectroscopy (TR-ARPES) of pumped excitonic systems. Including Coulomb electron-electron interactions at the Hartree-Fock (HF) level, our formalism captures the formation of excitonic bound states under the application of pump pulses. Considering a prototypical two-dimensional two-band semiconductor, we analyze the equilibrium phase diagram, which shows the expected transition from a semiconducting to an excitonic-insulator phase as the Coulomb interaction strength or its range increase. Out of equilibrium, we find that when the pump frequency is resonant with an excitonic mode, coherent oscillations of the excitonic order parameter persist after the pump pulse subsides and give rise to clear Floquet sidebands in the TR-ARPES spectrum. These exciton-field-induced sidebands are distinct from those originating from the pump laser field. We also identify band-resonance-induced sidebands arising from residual coherences at momenta where the band gap is resonant with the pump frequency. Finally, we analyze the local Coulomb interaction limit. Our results corroborate recent experimental observations of exciton-field-induced Floquet-like sidebands and establish DPOA as an efficient and accurate method for simulating ultrafast phenomena in interacting electron systems.

Localised surface deformation beneath frictional contacts generates a tribolayer whose microstructure and properties differ from the bulk. In austenitic stainless steels, this tribolayer forms through two competing martensitic transformation pathways. Here, these pathways are isolated in 316H stainless steel using in-situ synchrotron X-ray nanodiffractometry combined with nanoscratch testing, which together yield spatial maps of the evolving strain field beneath a single sliding asperity. Finite element modelling interprets the resulting distribution of martensitic phases, revealing a pressure driven pathway selection where hydrostatic compression ahead of the contact suppresses $\alpha'$ formation and favours the $\gamma \rightarrow \varepsilon$ transformation, while lateral sliding relieves this constraint and introduces a shear strain driving $\varepsilon \rightarrow \alpha'$ , producing an overall sequential $\gamma \rightarrow \varepsilon \rightarrow \alpha'$ pathway in the tribolayer. Where hydrostatic constraint persists, $\varepsilon$-martensite is retained; where material piles up and is unconstrained above the surface, the transformation proceeds directly to $\alpha'$. The $\gamma$-austenite adjacent to $\alpha'$- martensite shows elevated dislocation density, indicating that $\alpha'$ formation is accommodated by plastic deformation in the surrounding matrix. This distinction could explain differences in galling performance among iron-based and cobalt-based hardfacing alloys, where the $\varepsilon$-martensite forming cobalt alloys offer superior galling resistance. The methodology presented resolves transient microstructural states inaccessible to static measurements of macroscale, multiple asperity contacts, establishing a route to mechanistic insight across tribological phenomena more broadly.

The magnetism in NaV2O5 results from doping of the narrow split-off conduction band of V2O5, which becomes half-filled and leads to a Mott-insulating splitting of spin resolved bands with anti-ferromagnetic order of the spins along the zigzag chains. In the Pmmn structure the spin of this S = 1/2 system is equally shared between two vanadium atoms, residing in a molecular orbital type state. While below 34 K a charge disproportionation occurs into V4+ and V5+, the situation above this temperature is less clear and amounts to a fluctuating moment with equal probability of occupancy of each V. While traditionally described as a quarter-filled ladder system with electron spin localized on the rungs of the ladder, we here take a distributed moment approach in terms of the spin density lumped into individual atomic magnetic sites, including the small induced moments on the oxygen atoms. Exchange interactions are calculated between these sites using a linear response approach based on quasiparticle-self-consistent GW band structures. Surprisingly we find the exchange interactions between the small magnetic moments induced on the vanadyl and bridge oxygen sites to be larger than the exchange interactions between vanadium atoms. Their role in the critical temperature is found to be crucial. The spin wave spectra obtained from this classical Heisenberg type Hamiltonian contains unusual optic spin wave type collective excitations of high energy, the significance of which is discussed.

We investigate the statistical properties of random quadrangular surfaces generated by different randomization procedures: the Gruzberg-Klümper-Nuding-Sedrakyan (GKNS) construction, and two newly introduced generalizations of dynamical triangulations (DT), dynamical (DQ) and general quadrangulations (GQ). We formulate these surfaces within a unified graph-theoretic framework and establish the relationships between the elementary operations defining the different ensembles. For GKNS surfaces, we demonstrate that the construction is equivalent to two mutually constrained percolation processes and determine the associated critical point and critical exponents, revealing deviations from ordinary percolation. For DQ and GQ, we analyze the underlying Markov chains and determine the scaling of mixing and relaxation times. We further analyze all three ensembles through their degree distributions, degree correlations, distance statistics, and Hausdorff dimensions. While DQ exhibits exponentially decaying degree distributions and geometric properties similar to DT, GKNS and GQ display broad, scale-free degree distributions. Moreover, GKNS surfaces possess an asymptotic Hausdorff dimension $\Delta_H\approx 2$, whereas DQ and GQ approach $\Delta_H\approx 4$, similarly to DT. This indicates that DQ is compatible with the universal behavior of DT, while GKNS and GQ define distinct classes of random geometry, implying a different underlying measure in the space of random surfaces and a possible geometric framework for a new class of noncritical string theories.

The La$_2$NiO$_4$ compound stabilizes in nature in the so-called T structure with octahedral oxygen coordination of the Ni site. Motivated by a similarly existing polymorph for La$_2$CuO$_4$ in the cuprate system, we here study La$_2$NiO$_4$ in the T$^\prime$-structure with square-planar oxygen coordination of Ni by means of first-principles many-body theory. The hypothetical T$^\prime$-La$_2$NiO$_4$ compound turns out to be a manifest charge-transfer insulator with a cuprate-like charge gap of $\sim 1.8$ eV. Upon doping, a strong carrier asymmetry is revealed, i.e. while holes dominantly enter O$(2p)$-derived states, electrons may become itinerant majorly within effective Ni-$d_{x^2-y^2}$ states. Nearest-neighbor antiferromagnetic ordering at stoichiometry appears absent in the T$^\prime$ structure, in stark contrast to the strong antiferromagnetism in the T structure. Our theoretical study opens up new pathways for correlation physics in layered nickelates with challenging charge-transfer signatures, awaiting experimental inquiries.

We investigate the $n$-time cumulant generating function (or $n$-Full Counting Statistics, $n$-FCS) of extensive $U(1)$ charges following a quantum quench. Exploiting space-time duality we characterise this function when evolving from initial states that are symmetric under the action of the charge. In particular, we show that if the correlations in time are sufficiently weak, e.g.\ the transport is ballistic, the $n$-FCS factorises into a sum of single-time FCS arranged in a time-shell structure. A direct implication of this structure is a drastic simplification of dynamical correlation functions: in the presence of time ordering they only depend on the smallest time entering the correlator. We support these findings with several analytical and numerical tests performed in free and interacting models.

When electrons are subjected simultaneously to a magnetic field and a periodic potential, they form the fractal Hofstadter spectrum, whose topological gaps host quantum Hall and Chern insulating states with distinct Chern numbers. While electrical transport has established the topology of these states, whether their heat transport is likewise universal has remained unexplored. Here, we measure the thermal conductance of quantum Hall, Chern insulator, and interaction-driven symmetry-broken Chern insulator states in a bilayer graphene-hexagonal boron nitride moiré superlattice with a moirè wavelength of $\sim$14 nm using Johnson-noise thermometry. We find that the thermal conductance ($G_Q$) is quantized in units of the thermal conductance quantum ($G_Q = t\kappa_0T$) and is determined solely by the Chern number ($t$), independent of the microscopic origin of the topological state. By directly revealing universal topological heat transport in Hofstadter bands, our work establishes thermal conductance as a stringent probe of moiré topological matter and provides a route to investigating more exotic phases, including fractional Chern insulators.