arXiv subjects

P. I. Glicofridis

Publications and source records attributed to P. I. Glicofridis.

6 recordsLinked to original sources

arXiv2002

Modeling Subsurface Charge Accumulation Images of a Quantum Hall Liquid

Subsurface Charge Accumulation imaging is a cryogenic scanning probe technique that has recently been used to spatially probe incompressible strips formed in a two-dimensional electron system (2DES) at high magnetic fields. In this paper, we present detailed numerical modeling of these data. At a basic level, the method produces results that agree well with the predictions of models based on simple circuit elements. Moreover, the modeling method is sufficiently advanced to simulate the spatially resolved measurements. By comparing directly the simulations to the experimentally measured data, we can extract quantitatively local electronic features of the 2DES. In particular, we deduce the electron density of states inside the incompressible strips and electrical resistance across them.

cond-mat.mes-hall↗

arXiv2001

Direct observation of the charging of a 2D electron gas through an incompressible strip in the quantum Hall regime

Using charge accumulation imaging, we measure the charge flow across an incompressible strip and follow its evolution with magnetic field. The strip runs parallel to the edge of a gate deposited on the sample and forms at positions where an exact number of integer Landau levels is filled. An RC model of charging fits the data well and enables us to determine the longitudinal resistance of the strip. Surprisingly, we find that the strip becomes more resistive as its width decreases.

cond-mat.mes-hall↗

arXiv2000

Topographic Mapping of the Quantum Hall Liquid using a Few-Electron Bubble

A scanning probe technique was used to obtain a high-resolution map of the random electrostatic potential inside the quantum Hall liquid. A sharp metal tip, scanned above a semiconductor surface, sensed charges in an embedded two-dimensional electron gas. Under quantum Hall effect conditions, applying a positive voltage to the tip locally enhanced the 2D electron density and created a ``bubble'' of electrons in an otherwise unoccupied Landau level. As the tip scanned along the sample surface, the bubble followed underneath. The tip sensed the motions of single electrons entering or leaving the bubble in response to changes in the local 2D electrostatic potential.

cond-mat.mes-hall↗

arXiv1999

Imaging of Low Compressibility Strips in the Quantum Hall Liquid

Using Subsurface Charge Accumulation scanning microscopy we image strips of low compressibility corresponding to several integer Quantum Hall filling factors. We study in detail the strips at Landau level filling factors $ν=$ 2 and 4. The observed strips appear significantly wider than predicted by theory. We present a model accounting for the discrepancy by considering a disorder-induced nonzero density of states in the cyclotron gap.

cond-mat.mes-hall↗

arXiv1998

Subsurface charge accumulation imaging of a quantum Hall liquid

The unusual properties of two-dimensional electron systems that give rise to the quantum Hall effect have prompted the development of new microscopic models for electrical conduction. The bulk properties of the quantum Hall effect have also been studied experimentally using a variety of probes including transport, photoluminescence, magnetization, and capacitance measurements. However, the fact that two-dimensional electron systems typically exist some distance (about 100 nm) beneath the surface of the host semiconductor has presented an important obstacle to more direct measurements of microscopic electronic structure in the quantum Hall regime. Here we introduce a cryogenic scanning-probe technique-- subsurface charge accumulation imaging-- that permits very high resolution examination of systems of mobile electrons inside materials. We use it to image directly the nanometer-scale electronic structures that exist in the quantum Hall regime.

cond-mat.mes-hall↗

arXiv1997

Universal Linear Density of States for Tunneling into the Two-Dimensional Electron Gas in a Magnetic field

A new technique permits high fidelity measurement of the tunneling density of states (TDOS) of the two-dimensional electron gas. The obtained TDOS contains no distortions arising from low 2D in-plane conductivity and includes the contribution from localized tunneling sites. In a perpendicular magnetic field, a pseudogap develops in the TDOS at the Fermi level. Improved sensitivity enables resolution of a linear dependence of the TDOS on energy near the Fermi energy. The slopes of this linear gap are strongly field dependent. The data are suggestive of a new model of the gap at low energies.

cond-mat.mes-hall↗