arXiv subjects

Leonardo R. Cadorim

Publications and source records attributed to Leonardo R. Cadorim.

4 recordsLinked to original sources

arXiv2026

Imaging superconducting weak spots through vortex-assisted THz near-field photovoltage

Nanoscale inhomogeneities are a defining feature of many superconducting materials, yet their local electromagnetic response has remained difficult to access experimentally. This is because their relevant energy scale lies in the terahertz range, where wavelengths -- on the order of hundreds of microns -- are too large to spatially resolve nanoscopic variations. Here, we demonstrate the first application of THz near-field photovoltage nanoscopy in a superconductor, achieving 300 nm spatial resolution at 2.52 THz. Scanning a current-biased NbN strip, we reveal photovoltage peaks within the bulk associated with nanoscopic defects of reduced superfluid density. The observed photovoltage follows the evolution of the vortex-dissipative state and is attributed to enhanced vortex-antivortex pair nucleation at defect sites. Together, these results open a direct route to probing how material inhomogeneities influence light-matter interactions in superconductors, with implications for superconducting devices and strongly inhomogeneous systems such as high-Tc and moiré materials.

cond-mat.supr-con↗

arXiv2024

Stability limits in two-band superconductor rings

This study explores transitions between states with different winding number in two-band superconducting rings. From the time-dependent Ginzburg-Landau (TDGL) equations for two-component superconductors, we apply linear instability theory and develop a semi-analytical method that provides the critical flux for phase-slip occurrence. The developed method was applied to investigate how the critical flux depends on physical properties, such as band parameters and temperature. Finally, we show the possible existence of a soliton state, in which the phase winding number is different in each condensate.

cond-mat.supr-con↗

arXiv2022

Vortical versus skyrmionic states in the topological phase of a twisted bilayer with $d$-wave superconducting pairing

It was recently shown that a chiral topological phase emerges from the coupling of two twisted monolayers of superconducting Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ for certain twist angles. In this work, we reveal the behavior of such twisted superconducting bilayers with $d_{x^2-y^2}$ pairing symmetry in presence of applied magnetic field. Specifically, we show that the emergent vortex matter can serve as smoking gun for detection of topological superconductivity in such bilayers. Moreover, we report two distinct skyrmionic states that characterize the chiral topological phase, and provide full account of their experimental signatures and their evolution with the twist angle.

cond-mat.supr-con↗

arXiv2020

The intermediate type-I superconductors in the mesoscopic scale

M. Tinkham and P. G. de Gennes, described in their books the existence of an intermediate type-I superconductor as a consequence of an external surface that affects the well known classification of superconductors into type-I and II. Here we consider the mesoscopic superconductor where the ratio volume to area is small and the effects of the external surface are enhanced. By means of the standard Ginzburg-Landau theory the Tinkham-de Gennes scenario is extended to the mesoscopic type-I superconductor. We find new features of the transition at the passage from the genuine to the intermediate type-I. The latter has two distinct transitions, namely, from a paramagnetic to diamagnetic response in descending field and a quasi type-II behavior as the critical coupling is approached in ascending field. The intermediate type-I phase proposed here, and its corresponding transitions, reflect intrinsic features of the superconductor and not its geometrical properties.

cond-mat.supr-con↗