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Jongsoo Yoon

Publications and source records attributed to Jongsoo Yoon.

10 recordsLinked to original sources
arXiv2010

Theoretical Analysis of Drag Resistance in Amorphous Thin Films Exhibiting Superconductor-Insulator-Transition

The magnetical field tuned superconductor-insulator transition in amorphous thin films, e.g., Ta and InO, exhibits a range of yet unexplained curious phenomena, such as a putative low-resistance metallic phase intervening the superconducting and the insulating phase, and a huge peak in the magnetoresistance at large magnetic field. Qualitatively, the phenomena can be explained equally well within several significantly different pictures, particularly the condensation of quantum vortex liquid, and the percolation of superconducting islands embedded in normal region. Recently, we proposed and analyzed a new measurement that should be able to decisively point to the correct picture: a drag resistance measurement in an amorphous thin-film bilayer setup. Neglecting interlayer tunneling, we found that the drag resistance within the vortex paradigm has opposite sign and is orders of magnitude larger than that in competing paradigms. For example, two identical films as in Sambandamurthy et al. 2004 with 25 nm layer separation at 0.07 K would produce a drag resistance $\sim10^{-4}Ω$ according the vortex theory, but only $\sim10^{-12}Ω$ for the percolation theory. We provide details of our theoretical analysis of the drag resistance within both paradigms, and report some new results as well.

cond-mat.supr-con↗
arXiv2009

Investigating superconductor-insulator transition in thin films using drag resistance:Theoretical analysis of a proposed experiment

The magnetically driven superconductor-insulator transition in amorphous thin films (e.g., InO, Ta) exhibits several mysterious phenomena, such as a putative metallic phase and a huge magnetoresistance peak. Unfortunately, several conflicting categories of theories, particularly quantum-vortex condensation, and normal region percolation, explain key observations equally well. We propose a new experimental setup, an amorphous thin-film bilayer, where a drag resistance measurement would clarify the role quantum vortices play in the transition, and hence decisively point to the correct picture. We provide a thorough analysis of the device, which shows that the vortex paradigm gives rise to a drag with an opposite sign and orders of magnitude larger than the drag measured if competing paradigms apply.

cond-mat.supr-con↗
arXiv2009

Transport Phase Diagram of Homogeneously Disordered Superconducting Thin Films

We have constructed a phase diagram in temperature-magnetic field-disorder space for homogeneously disordered superconducting tantalum thin films. Phases are phenomenologically identified by the nonlinear transport characteristics that are unique in each phase. The resulting phase diagram shows that a direct superconductor-insulator transition is prohibited at any disorder because the superconducting phase is completely surrounded by the intervening metallic phase.

cond-mat.supr-con↗
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↗
arXiv2006

Magnetically Induced Metallic Phase in Superconducting Tantalum Films

We have studied the electronic transport properties of homogeneously disordered superconducting tantalum thin films in magnetic fields. The films exhibit three distinct transport regimes in the zero temperature limit which we identify as superconducting, metallic, and insulating phases. The metallic phase is unexpected. The transport characteristics of this metallic phase are found to be similar to those of MoGe films and high mobility dilute two-dimensional electrons or holes confined in semiconductor interface or transistor geometry.

cond-mat.supr-con↗
arXiv2005

Current-induced suppression of superconductivity in tantalum thin films at zero magnetic field

We report our findings on the mechanism of current-induced suppression of superconductivity in amorphous tantalum films as thin as 5nm under zero applied magnetic field. Our results indicate that the applied current generates magnetic vortices threading the films, and the dynamics of these vortices leads to the suppression of the superconductivity. Our findings also imply that the motion of current-generated magnetic vortices gives rise to nonlinear transport of which characteristics closely resemble those expected in Kosterlitz-Thouless theories with strong finite size effects.

cond-mat.supr-con↗
arXiv2001

Non-monotonic magnetic field and density dependence of in-plane magnetoresistance in dilute two-dimensional holes in GaAs/AlGaAs

We studied low temperature (T=50mK) in-plane magnetoresistance of a dilute two-dimensional hole system in GaAs/AlGaAs heterostructure that exhibits an apparent metal-insulator transition. We found an anisotropic magnetoresistance, which changes dramatically at high in-plane fields ($B_{\parallel}\agt$5T) as the hole density is varied. At high densities where the system behaves metallic at $B_{\parallel}=0$, the transverse magnetoresistance is larger than the longitudinal magnetoresistance. With decreasing the hole density the difference becomes progressively smaller, and at densities near the "critical" density and lower, the longitudinal magnetoresistance becomes larger than the transverse magnetoresistance.

cond-mat.mes-hall↗
arXiv1998

Wigner crystallization and metal-insulator transition of two-dimensional holes in GaAs/AlGaAs at B=0

We report the transport properties of a low disorder two-dimensional hole system (2DHS) in the GaAs/AlGaAs heterostructure, which has an unprecedentedly high peak mobility of $7\times 10^5cm^2/Vs$, with hole density of $4.8\times 10^9 cm^{-2}<p<3.72\times 10^{10}cm^{-2}$ in the temperature range of $50mK<T<1.3K$. From their T, p, and electric field dependences, we find that the metal-insulator transition in zero magnetic field in this exceptionally clean 2DHS occurs at $r_s=35.1\pm0.9$, which is in good agreement with the critical $r_s$ for Wigner crystallization ${r_s}^c=37\pm 5$, predicted by Tanatar and Ceperley for an ideally clean 2D system.

cond-mat↗