arXiv subjects

Dragana Popovic

Publications and source records attributed to Dragana Popovic.

23 records · Page 2Linked to original sources

arXiv1999

Effect of Local Magnetic Moments on the Metallic Behavior in Two Dimensions

The temperature dependence of conductivity $σ(T)$ in the metallic phase of a two-dimensional electron system in silicon has been studied for different concentrations of local magnetic moments. The local moments have been induced by disorder, and their number was varied using substrate bias. The data suggest that in the limit of $T\to 0$ the metallic behavior, as characterized by $dσ/dT < 0$, is suppressed by an arbitrarily small amount of scattering by local magnetic moments.

cond-mat.dis-nn↗

arXiv1997

Conductance Fluctuations Near the Two-Dimensional Metal-Insulator Transition

Measurements of conductance $G$ on short, wide, high-mobility Si-MOSFETs reveal both a two-dimensional metal-insulator transition (MIT) at moderate temperatures (1 $<~ T <$ 4~K) and mesoscopic fluctuations of the conductance at low temperatures ($T~ <$ 1~K). Both were studied as a function of chemical potential (carrier concentration $n_s$) controlled by gate voltage ($V_g$) and magnetic field $B$ near the MIT. Fourier analysis of the low temperature fluctuations reveals several fluctuation scales in $V_g$ that vary non-monotonically near the MIT. At higher temperatures, $G(V_g,B)$ is similar to large FETs and exhibits a MIT. All of the observations support the suggestion that the MIT is driven by Coulomb interactions among the carriers.

cond-mat.str-el↗

arXiv1997

Metal-Insulator Transition in a Low-Mobility Two-Dimensional Electron System

We have varied the disorder in a two-dimensional electron system in silicon by applying substrate bias. When the disorder becomes sufficiently low, we observe the emergence of the metallic phase, and find evidence for a metal-insulator transition (MIT): the single-parameter scaling of conductivity with temperature near a critical electron density. We obtain the scaling function $β$, which determines the length (or temperature) dependence of the conductance. $β$ is smooth and monotonic, and linear in the logarithm of the conductance near the MIT, in agreement with the scaling theory for interacting systems.

cond-mat.str-el↗

arXiv1997

Comment on ``Electric Field Scaling at B=0 Metal-Insulator Transition in Two Dimensions''

In a recent Letter, Kravchenko et al. [cond-mat/9608101] have provided evidence for a metal-insulator transition (MIT) in a two-dimensional electron system (2DES) in Si metal-oxide-semiconductor field-effect transistors (MOSFETs). The transition observed in these samples occurs at relatively low electron densities $n_{s}\sim (1-2)\times 10^{11}cm^{-2}$ and high disorder $σ_{c}\sim e^{2}/2h$. We present evidence for a 2D MIT in a structure where the disorderis about two orders of magnitude weaker than in Si MOSFETs. The MIT occurs in the same range of $n_s$ Providing very strong evidence that the 2D MIT in Si-based devices is caused by electron-electron interactions.

cond-mat.str-el↗

arXiv1997

Minimum Metallic Mobility in a Two-Dimensional Electron Gas

We report the observation of a metal-insulator transition in a two-dimensional electron gas in silicon. By applying substrate bias, we have varied the mobility of our samples, and observed the creation of the metallic phase when the mobility was high enough ($μ~> 1 m^2/Vs$), consistent with the assertion that this transition is driven by electron-electron interactions. In a perpendicular magnetic field, the magnetoconductance is positive in the vicinity of the transition, but negative elsewhere. Our experiment suggests that such behavior results from a decrease of the spin-dependent part of the interaction in the vicinity of the transition.

cond-mat.str-el↗