2026

Levitons are minimal-excitation electronic wave packets generated by Lorentzian voltage pulses and constitute a central resource for electron quantum optics. Their creation and defining properties are usually formulated in continuum scattering descriptions, whereas many candidate platforms for integrated electronic quantum circuits are finite, discrete, and strongly shaped by lattice dispersion. We study leviton generation in finite one-dimensional tight-binding chains of non-interacting fermions driven by time-dependent voltage pulses. Using the single-particle density matrix, we resolve the excitation above the initial Fermi sea and quantify its quality through the average excitation number and its fluctuations. We find that clean leviton-like states emerge only in an intermediate regime where the pulse is slow enough to be resolved by the dynamics on the lattice, but not so slow that truncation and finite-size effects distort the Lorentzian profile in the time domain. Lorentzian pulses (even if truncated) systematically outperform non-Lorentzian pulse shapes in approaching the low-noise limit with increasing system size. We further identify finite-lattice signatures associated with band filling, pulse amplitude, linear voltage-drop geometry, and residual deviations from the continuum integer-charge condition. These results establish a microscopic framework for understanding leviton formation beyond the ideal continuum limit and for evaluating lattice-based platforms for coherent few-electron transport.

As minimal cells or protocells are dramatically simpler than modern unicells it is possible to quantitatively estimate free energy changes for every process in the lifecycle of a protocell and compare these with estimates of the free energy changes for lifecycles in modern unicells. We present quantitative estimates of all metabolic changes in part by new density function theory (DFT) estimations, in part by compiling previously measured or estimated free energy changes, and in part by new thermodynamic calculations for all self-assembly, vesicle bending, and fission energies.

Open-shell nanographenes provide a versatile platform to host unconventional magnetic states within their π-conjugated networks. Particularly appealing are graphene architectures that incorporate spatially separated radicals and tunable interactions, offering a scalable route toward spin-based quantum architectures. Triangulenes are ideal for this purpose, as their radical count scales with size, although strong hybridization prevents individual spin control. Here, we realize a radical reconfiguration strategy that transforms a single-radical aza-triangulene into a frustrated antiferromagnetic triradical by covalently extending it with armchair anthene moieties of increasing length. Scanning tunnelling spectroscopy reveals edge-localized Kondo resonances and a doublet-to-quartet spin excitation, evidencing the emergence of correlated spins. Multi-reference electronic-structure calculations trace the progressive increase in polyradical character with anthene length, driven by the clustering of frontier states within a narrow energy window. Consequently, the initial single-radical doublet reorganizes into a frustrated triradical with weakly coupled edge spins, a molecular analog of a three-qubit quantum register.

We develop a microscopic model to investigate current-induced light emission in single-molecule tunnel junctions, where a two-level system interacts with a plasmonic field. Using the quantum master equation, we explore the transition from weak to strong plasmon-molecule coupling, identifying three distinct regimes governed by cooperativity, which quantifies the interplay between interaction strength and losses. Our findings establish a framework to detect strong coupling, unveiling resonance-dependent features in the emission spectrum and photon correlations.

In molecular electronics, the development of molecular wires capable of carrying high electrical current with minimal loss remains a central challenge, despite extensive efforts in both solution-phase and ultrahigh-vacuum synthesis. Graphene nanoribbons (GNRs) with their structural robustness and tunable electronic properties have emerged as promising candidates. In particular, topologically engineered GNRs with atomically precise edge modifications offer new routes for efficient charge transport. Here, we systematically investigate the transport properties of a staggered, edge-extended GNR based on a 7-AGNR backbone, denoted as 7-AGNR-S(1,3), using low-temperature scanning tunneling microscopy liftoff experiments. Under favorable junction conditions, the conductance remains nearly constant during tip retraction over junction lengths exceeding 10 nm, mediated by the low-energy bands arising from the coupled topological zero-energy edge states. Additionally, we developed a detailed model of the liftoff process and simulated charge transport, revealing the roles of delocalized valence band states and showing how local potential variations at the electrode interfaces can modulate molecular-level alignment and conductance. Our findings underscore the importance of interface engineering in the design of high-performance molecular electronic devices.

Open-shell nanographenes offer a controlled setting to study correlated magnetism emerging from π-electron systems. Here, we study non-bipartite Fermi-Hubbard ladders describing oligo(indenoindene) molecules. These feature a gapped, weakly dispersing manifold of quasizero modes in their single-particle spectra, and we show that their low-energy properties can be effectively mapped onto an interacting set of spin-1/2 degrees of freedom. Using density matrix renormalization group simulations of the full Fermi-Hubbard model, we obtain their excitation spectra, entanglement profiles, and spin-spin correlations. We then construct optimized delocalized fermionic modes that act as emergent spins and demonstrate that their interactions are well described by a frustrated J₁-J₂ Heisenberg chain. This effective description clarifies how spin degrees of freedom arise and interact in non-bipartite nanographene ladders, providing a compact and accurate representation of their correlated behavior.

While the flexibility of a CO-functionalized tip in scanning probe methods is at the origin of extraordinarily high resolution in imaging, its impact on inelastic electron tunneling spectroscopy has remained unexplored to date. Here, coupled vibrational modes of a CO molecule bonded to the tip of a scanning tunneling microscope and a single melamine isomer on Cu(001) are studied in a combined experimental and theoretical work. Decreasing the distance between CO and the adsorbed isomer causes a substantial tilt of the CO molecule, which reduces the symmetry of the junction geometry and thereby lifts the degeneracy of the CO frustrated translation modes. The entailed blueshift of the CO vibrational mode depends on the isomer and reflects the different local interactions between the molecules. The findings of this work are applicable to a general class of molecular adsorbates and pave the way for establishing inelastic electron tunneling spectroscopy as a useful characterization tool in surface physics and chemistry.