Diego Rabelo da Costa

Ion transport in crystalline hosts is controlled by an applied potential that simultaneously sets ionic distribution and transport rate, restricting operation to a one-dimensional control space. Here we show that the transport rate of Li+ ions in double-gated van der Waals devices can be modulated while the system occupies fixed ionic-density states. We measure the ionic current along the van der Waals interfaces between hexagonal boron nitride and graphene or MoS2 while simultaneously monitoring the in-plane electronic response. The ionic current exhibits pronounced hysteresis, with plateaus marking discrete ionic-density states balanced by electronic charge, while an independently tunable electrochemical-potential drop controls the ionic transport rate. The devices sustain over 1,000 switching cycles and function as hybrid ionic–electronic transistors capable of logic operations and memory retention, with ON/OFF ratios exceeding 2 orders of magnitude. This work demonstrates a two-dimensional control space for ions intercalated in layered materials.

Carbon nanotubes (CNTs) constitute a highly tunable platform for probing the interplay between structural chirality and quantum transport in quasi-one-dimensional systems. Here, we perform a systematic study of the nonequilibrium orbital response across a broad set of metallic and semiconducting chiral CNTs. We find that the orbital Edelstein susceptibility depends strongly on both chirality and nanotube diameter, revealing that the orbital response cannot be captured by a universal scaling law. Instead, distinct families of CNTs emerge, forming characteristic orbital-response branches uniquely determined by the chiral wrapping vector. We further investigate the role of metallic contacts on orbital-current generation and orbital selectivity. While metallic CNTs rapidly recover their intrinsic orbital response away from the contact region, semiconducting CNTs display pronounced oscillatory behavior arising from interference between transport channels carrying different angular momenta injected by wide-band metallic contacts. Finally, by incorporating angular correlations into the contact self-energy, we demonstrate that chiral CNTs can operate as efficient orbital angular momentum filters, selectively transmitting orbitally textured electronic states in accordance with the crystal angular momentum of the propagating bands.

Andreev reflection at a normal/superconductor interface is studied in a system in which the normal region consists of a few-layer black phosphorus (BP) under an electric field applied perpendicularly to the material’s plane. The application of a strong electric field induces a phase transition, closing the BP gap and forming Dirac cones that preserve the unbiased material’s inherent anisotropic dispersion. This platform allows us to explore the effect of electric-field-tunable anisotropy on the Andreev reflection of massless Dirac quasiparticles, using a wave-packet time-evolution method. Our results show that the anisotropy of a BP electronic structure plays a central role in Andreev reflection, which results in a voltage–transmission relation that, in contrast to the case of isotropic materials, strongly depends on the wave vector angle and weakly depends on the Fermi level away from the superconducting gap, (i.e., for retro-reflection processes).

We investigate the nonequilibrium phase diagram of the two-dimensional ferromagnetic spin-1 Blume-Capel model driven by competing stochastic dynamics. The system is simultaneously coupled to a thermal reservoir, modeled by single-spin-flip Glauber dynamics via the Metropolis algorithm, and subjected to a continuous external energy flux, simulated by two-spin-exchange Kawasaki dynamics. Using extensive Monte Carlo simulations, we characterize the stationary states, phase transitions, and the rich phase-diagram topology induced by this dynamical competition. Despite the ferromagnetic nature of the exchange interactions, the interplay between thermal relaxation and energy injection induces nonequilibrium self-organization, leading to the emergence of partially and fully ordered antiferromagnetic phases. Furthermore, we demonstrate that systematically varying the single-ion anisotropy shifts the position of the tricritical point and alters the extent of metastable regions exhibiting thermal hysteresis. Remarkably, finite-size scaling analyses reveal that even in the presence of steady energy fluxes and detailed-balance violation, the critical exponents of the continuous transitions remain consistent with the equilibrium two-dimensional Ising universality class to within numerical accuracy.