arXiv subjects

C. L. Vicente

Publications and source records attributed to C. L. Vicente.

6 recordsLinked to original sources

arXiv2009

Scaling in Plateau-to-Plateau Transition: A Direct Connection of Quantum Hall Systems with Anderson Localization Model

The quantum Hall plateau transition was studied at temperatures down to 1 mK in a random alloy disordered high mobility two-dimensional electron gas. A perfect power-law scaling with κ=0.42 was observed from 1.2K down to 12mK. This perfect scaling terminates sharply at a saturation temperature of T_s~10mK. The saturation is identified as a finite-size effect when the quantum phase coherence length (L_ϕ ~ T^{-p/2}) reaches the sample size (W) of millimeter scale. From a size dependent study, T_s \propto W^{-1} was observed and p=2 was obtained. The exponent of the localization length, determined directly from the measured κand p, is ν=2.38, and the dynamic critical exponent z = 1.

cond-mat.mes-hall↗

arXiv2006

Evidence of spatial inhomogeneity near the onset of magnetically induced insulating state in superconducting thin films

Non-monotonic differential resistance (dV/dI) is observed in magnetically induced insulating films which exhibit apparent superconductor-metal-insulator transitions in the low temperature limit; at low bias currents the nonlinear transport is insulator-like while at high bias currents it is characteristic of metallic phase. The non-monotonic dV/dI may be evidence that the insulating state consists of metallic domains connected by point contacts (insulating gaps), implying that spatial inhomogeneities play a dominant role in determining the nature of the apparent metal-insulator transition.

cond-mat.supr-con↗

arXiv2006

Non-thermal origin of nonlinear transport across magnetically induced superconductor-metal-insulator transition

We have studied the effect of perpendicular magnetic fields and temperatures on the nonlinear electronic transport in amorphous Ta superconducting thin films. The films exhibit a magnetic field induced metallic behavior intervening the superconductor-insulator transition in the zero temperature limit. We show that the nonlinear transport in the superconducting and metallic phase is of non-thermal origin and accompanies an extraordinarily long voltage response time.

cond-mat.supr-con↗

arXiv2005

The A-B Transition of Superfluid Helium-3 in Aerogel and the Effect of Anisotropic Scattering

We report the results of high frequency acoustic shear impedance measurement on superfluid helium-3 confined in 98% porosity silica aerogel. Using 8.69 MHz continuous wave excitation, we measured the acoustic shear impedance as a function of temperature for the sample pressure of 28.4 and 33.5 bar. We observed the A-B transition on warming in zero magnetic field. Our observations show that the A and B phases in aerogel coexist in a temperature range of about 100 micro-Kelvin in width. We propose that the difference in the relative stability of the A and B phases, arising from anisotropic scattering, can account for our observations.

cond-mat.other↗

arXiv2005

Quantization of the diagonal resistance: Density gradients and the empirical resistance rule in a 2D system

We have observed quantization of the diagonal resistance, R_xx, at the edges of several quantum Hall states. Each quantized R_xx value is close to the difference between the two adjacent Hall plateaus in the off-diagonal resistance, R_xy. Peaks in R_xx occur at different positions in positive and negative magnetic fields. Practically all R_xx features can be explained quantitatively by a ~1%/cm electron density gradient. Therefore, R_xx is determined by R_xy and unrelated to the diagonal resistivity rho_xx. Our findings throw an unexpected light on the empirical resistivity rule for 2D systems.

cond-mat.mes-hall↗

arXiv2004

Tilt Induced Localization and Delocalization in the Second Landau Level

We have investigated the behavior of electronic phases of the second Landau level under tilted magnetic fields. The fractional quantum Hall liquids at $ν=$2+1/5 and 2+4/5 and the solid phases at $ν=$2.30, 2.44, 2.57, and 2.70 are quickly destroyed with tilt. This behavior can be interpreted as a tilt driven localization of the 2+1/5 and 2+4/5 fractional quantum Hall liquids and a delocalization through melting of solid phases in the top Landau level, respectively. The evolution towards the classical Hall gas of the solid phases is suggestive of antiferromagnetic ordering.

cond-mat.mes-hall↗