arXiv subjects

Jorge Estrada-Álvarez

Publications and source records attributed to Jorge Estrada-Álvarez.

4 recordsLinked to original sources

arXiv2026

Emergent Quantum Geometric Phases in Holey Graphene

In graphene and other two-dimensional materials, periodic modulations of the electron density can significantly alter the energy spectrum and transport properties. Here, we report magnetotransport measurements in encapsulated monolayer graphene with ultra-high-quality patterned periodic antidot lattices that preserve the intrinsic electronic properties of the material. This lithographically defined platform enables controlled access to commensurability and superlattice phenomena at length scales otherwise difficult to achieve. By systematically tuning the lattice dimensions, we reveal a hierarchy of classical commensurability features arising from cyclotron orbits with comparable radii that follow multiple classical trajectories, resulting in broadened resistance peaks beyond the conventional single-orbit picture. Superimposed on these features, we observe pronounced Brown-Zak oscillations arising from the quantum commensurability between the magnetic flux quantum and the unit cell of the engineered Bravais lattices. We demonstrate that the intrinsic geometric phase of our system is directly measurable and show a precise matching of the magnetic field periodicity to the lithographic periodic patterning, where moiré-like electronic spectra can be geometrically generated in single-layer graphene without the need for twist, lattice mismatch, or multilayer stacking. Our results establish nanopatterned graphene as a clean, tunable, and scalable platform for realizing and exploring moiré physics through on-demand real-space design

cond-mat.mes-hall↗

arXiv2025

Superballistic conduction in hydrodynamic antidot graphene superlattices

Viscous electron flow exhibits exotic signatures such as superballistic conduction. In order to observe hydrodynamics effects, a 2D device where the current flow is as inhomogeneous as possible is desirable. To this end, we build three antidot graphene superlattices with different hole diameters. We measure their electrical properties at various temperatures and under the effect of a perpendicular magnetic field. We find an enhanced superballistic effect, suggesting the effectiveness of the geometry at bending the electron flow. In addition, superballistic conduction, which is related to a transition from a non-collective to a collective regime of transport, behaves non-monotonically with the magnetic field. We also analyze the device resistance as a function of the size of the antidot superlattice to find characteristic scaling laws describing the different transport regimes. We prove that the antidot superlattice is a convenient geometry for realizing hydrodynamic flow and provide valuable explanations for the technologically relevant effects of superballistic conduction and scaling laws.

cond-mat.mes-hall↗

arXiv2025

Superballistic paradox in electron fluids: Evidence of tomographic transport

Electron hydrodynamics encompasses the exotic fluid-like behavior of electrons in two-dimensional materials such as graphene. It accounts for superballistic conduction, also known as the Gurzhi effect, where increasing temperature reduces the electrical resistance. In analogy with conventional fluids, the Gurzhi effect is only expected in the hydrodynamic regime, with the decrease in the resistance occurring at intermediate temperatures. Nonetheless, experiments on electron fluids consistently show that superballistic conduction starts at close-to-zero temperatures. To address this paradox, we study hydrodynamic flow, and we find that replacing the classical dynamics with tomographic dynamics, where only head-on collisions are allowed between electrons, solves the dilemma. The latter strengthens superballistic conduction, with potential applications in low-dissipation devices, and explains its differences with the Molenkamp effect and conventional fluids dynamics. Our study reveals that the superballistic paradox is resolved by considering the electrons not as classical particles but as fermions.

cond-mat.mes-hall↗

arXiv2024

Alternative routes to electron hydrodynamics

Viscous flow of interacting electrons in two dimensional materials features a bunch of exotic effects. A model resembling the Navier-Stokes equation for classical fluids accounts for them in the so called hydrodynamic regime. We performed a detailed analysis of the physical conditions to achieve electron hydrodynamic transport and found three new alternative routes: favouring frequent inelastic collisions, the application of a magnetic field or a high-frequency electric field. As a mayor conclusion, we show that the conventional requirement of frequent electron-electron collisions is too restrictive and, as a consequence, materials and phenomena to be described using hydrodynamics are widened. In view of our results, we discuss recent experimental evidence on viscous flow and point out alternative avenues to reduce electric dissipation in optimized devices.

cond-mat.mes-hall↗