arXiv subjects

B. C. Camargo

Publications and source records attributed to B. C. Camargo.

5 recordsLinked to original sources

arXiv2021

Magnetization of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$ micrometer thin ring and its depinning line

We demonstrate a geometrical effect on the depinning line (DL) of the flux line lattice of the Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$ high-T$_c$ superconductor (HTSC) micrometer ring. The DL shifts to notably lower temperatures in comparison to bulk crystals and thin flakes of the same sample. The shift is attributed to a decrease in the overall pinning potential due to a double size effect, namely: a) the ring thickness $\sim 1~μ$m being smaller than the pinning correlation length, and b) the increase in the effective London penetration depth of the vortices (Pearl vortices). The large shift of the DL to lower temperatures may influence the suitability of this HTSC for applications in microstrip antennas and THz emitters.

cond-mat.supr-con↗

arXiv2020

Upper critical field and superconductor-metal transition in ultrathin niobium films

Recent studies suggests that in disordered ultrathin films superconducting (SC) state may be intrinsically inhomogeneous. Here we investigate the nature of SC state in ultrathin Nb films, of thickness $d$ ranging from 1.2 nm to 20 nm, which undergo a transition from amorphous to polycrystalline structure at the thickness $d \simeq 3.3$ nm. We show that the properties of SC state are very different in polycrystalline and amorphous films. The upper critical field ($H_{c2}$) is orbitally limited in the first case, and paramagnetically limited in the latter. The magnetic field induced superconductor-metal transition is observed, with the critical field approximately constant or decreasing as a power-law with the film conductance in polycrystalline or amorphous films, respectively. The scaling analysis indicates distinct scaling exponents in these two types of films. Negative contribution of the SC fluctuations to conductivity exists above $H_{c2}$, particularly pronounced in amorphous films, signaling the presence of fluctuating Cooper pairs. These observations suggest the development of local inhomogeneities in the amorphous films, in the form of proximity-coupled SC islands. An usual evolution of SC correlations on cooling is observed in amorphous films, likely related to the effect of quantum fluctuations on the proximity-induced phase coherence.

cond-mat.supr-con↗

arXiv2018

Taming the magnetoresistance anomaly in graphite

At low temperatures, graphite presents a magnetoresistance anomaly which manifests as a transition to a high-resistance state (HRS) above a certain critical magnetic field $\text{B}_\text{c}$. Such HRS is currently attributed to a c-axis charge-density-wave taking place only when the lowest Landau level is populated. By controlling the charge carrier concentration of a gated sample through its charge neutrality level (CNL), we were able to experimentally modulate the HRS in graphite for the first time. We demonstrate that the HRS is triggered both when electrons and holes are the majority carriers but is attenuated near the CNL. Taking screening into account, our results indicate that the HRS possess a strong in-plane component and can occur below the quantum limit, being at odds with the current understanding of the phenomenon. We also report the effect of sample thickness on the HRS.

cond-mat.str-el↗

arXiv2018

Platinum tripods as nanometric frequency multiplexing devices

Electrical and structural characterization of nano-particles are very important steps to determine their potential applications in microelectronics. In this paper, we adress the crystallographic and electric transport properties of soft-chemistry-grown nanometric Pt tribranches. We report that Pt nanostars grown from the reduction of $\text{H}_{2}\text{PtCl}_6$ salt in pure oleylamine present a remarkable crystalline structure and a deeply metallic character despite being grown under mild conditions. We demonstrate that such devices are able to operate at current densities surpassing $200$ MA/$\text{cm}^2$, actuating as highly compact frequency multiplexers in the non-ohmic regime.

cond-mat.mes-hall↗

arXiv2018

Electrical properties of in-plane-implanted graphite nanoribbons

We studied the effect of low energy (30 keV) ionic implantation of Ga+ in the direction parallel to the graphene planes (perpendicular to c-axis) in oriented graphite ribbons with widths around 500 nm. Our experiments have reproducibly shown a reduction of electrical resistance upon implan- tation consistent with the occurrence of ionic channeling in our devices. Our results allow for new approaches in the modulation of the charge carrier concentration in mesoscopic graphite.

cond-mat.mes-hall↗