arXiv subjects

F. G. Pikus

Publications and source records attributed to F. G. Pikus.

10 recordsLinked to original sources

arXiv1997

Nanoscale Field-Effect Transistors: An Ultimate Size Analysis

We have used a simple, analytically solvable model to analyze the characteristic s of dual-gate metal-oxide-semiconductor field-effect transistors (MOSFETs) with 10-nm-scale channel length L. The model assumes ballistic dynamics of 2D electrons in an undoped channel between highly doped source and drain. When applied to silicon n-MOSFETs, calculations show that the voltage gain (necessary for logic applications) drops sharply at L ~ 10 nm, while the conductance modulation remains sufficient for memory applications until L ~ 4 nm.

cond-mat↗

arXiv1997

Weak Localization in Semiconductor Multi-Quantum Well Structures

We have studied the phenomenon of weak localization in multi-quantum-well (MQW) structures in the regime of weak tunneling, when superlattice minibands are not formed. We have calculated the effect of weak localization on conductivity, which in this situation is described by a system of coupled Dyson equations. The tunneling across the MQW structure is found, in general, to suppress the weak localization effect on conductivity.

cond-mat↗

arXiv1997

Statistics of the Charging Spectrum of a Two-Dimensional Coulomb Glass Island

The fluctuations of capacitance of a two-dimensional island are studied in the regime of low electron concentration and strong disorder, when electrons can be considered classical particles. The universal capacitance distribution is found, with the dispersion being of the order of the average. This distribution is shown to be closely related to the shape of the Coulomb gap in the one-electron density of states of the island. Behavior of the the capacitance fluctuations near the metal - insulator transition is discussed.

cond-mat↗

arXiv1996

Spin Splitting and Weak Localization in (110) GaAs/AlGaAs Quantum Wells

We investigate experimentally and theoretically the spin-orbit effects on the weak localization in a (110) GaAs 2-dimensional electron gas (2DEG). We analyze the role of two different terms in the spin splitting of the conduction band: the Dresselhaus terms, which arise due to the lack of inversion center in the bulk GaAs, and the Rashba terms, which are caused by the asymmetry of the quantum well. It is shown that in A3B5 quantum wells the magnetoresistance due to the weak localization depends qualitatively on the orientation of the well. In particular, it is demonstrated that the (110) geometry has a distinctive feature that in the absence of the Rashba terms the ``antilocalization'' effect, i.e. the positive magnetoresistance, does not exist. Calculation of the weak anti-localization magnetoresistance is found to be in excellent agreement with experiments.

cond-mat↗

arXiv1996

Single-Electron Charging and Coulomb Interaction in InAs Self-Assembled Quantum Dot Arrays

Sequential single-electron charging is observed in InAs Self-Assembled Quantum Dots using capacitance spectroscopy. In this system, the Coulomb energy is smaller than the inter-level energy spacings due to the quantum confinement and both effects can be separately identified. A theoretical model is proposed for this system and the capacitance experiments were devised in order to experimentally observe the effects of Coulomb interaction between electrons on the dots. The effects of inter- and intra-dot Coulomb interaction have been observed in the capacitanc e spectra. A good agreement between the proposed model and experiment is achieved.

cond-mat↗

arXiv1996

Conduction band spin splitting and negative magnetoresistance in ${\rm A}_3{\rm B}_5$ heterostructures

The quantum interference corrections to the conductivity are calculated for an electron gas in asymmetric quantum wells in a magnetic field. The theory takes into account two different types of the spin splitting of the conduction band: the Dresselhaus terms, both linear and cubic in the wave vector, and the Rashba term, linear in wave vector. It is shown that the contributions of these terms into magnetoconductivity are not additive, as it was traditionally assumed. While the contributions of all terms of the conduction band splitting into the D'yakonov--Perel' spin relaxation rate are additive, in the conductivity the two linear terms cancel each other, and, when they are equal, in the absence of the cubic terms the conduction band spin splitting does not show up in the magnetoconductivity at all. The theory agrees very well with experimental results and enables one to determine experimentally parameters of the spin-orbit splitting of the conduction band.

cond-mat↗

arXiv1996

Weak Localization and Negative Magnetoresistance in Wurtzite-type Crystals

We have developed a theory of the negative magnetoresistance due to the weak localization in uniaxial wurtzite-type crystals, in which the spin splitting of the conduction band is linear in the wave vector, unlike the cubic ${\rm A_3 B_5}$ crystals. Unlike earlier theories, we take into account the correlation between the electron motion in spin and co-ordinate spaces. It is shown that as a result of this correlation the magnetoresistance depends on the orientation of the magnetic field with respect to the main axis of the crystal even if the effective mass is isotropic. The new theory allows to accurately determine the value of the spin splitting constant in uniaxial crystals.

cond-mat↗

arXiv1996

Properties of Paired Quantum Hall States at $ν=2$

The energetic properties of a paired quantum Hall state at Landau level filling $ν=2$ are investigated using variational Monte Carlo techniques. Pairing is found to be energetically favorable in small magnetic fields because it introduces correlations between up and down spins that are absent in the traditional $ν=2$ state. We find that pairing survives extrapolation to the thermodynamic limit.

cond-mat↗

arXiv1996

Quantum melting on a lattice and a delocalization transition

We consider 2d gas of spinless fermions with the Coulomb interaction on a lattice at T=0 and at different values of the hopping amplitude J. At small J electrons form a periodic structure. At filling factor ν=1/6 this structure melts at J as low as 0.02--0.03 in units of the nearest-neighbor Coulomb energy. We argue that this transition is connected to the dielectric-metal and dielectric-superconductor transitions. To demonstrate this point we perform computer modeling of the systems 6x6 with 6 and 7 electrons and 6x12 with 12 electrons. By sweeping J we compute simultaneously persistent current and structural characteristics of the electron distribution.

cond-mat↗

arXiv1996

Weak Antilocalization and Spin Precession in Quantum Wells

The results of magnetoconductivity measurements in GaInAs quantum wells are presented. The observed magnetoconductivity appears due to the quantum interference, which lead to the weak localization effect. It is established that the details of the weak localization are controlled by the spin splitting of electron spectra. A theory is developed which takes into account both linear and cubic in electron wave vector terms in spin splitting, which arise due to the lack of inversion center in the crystal, as well as the linear terms which appear when the well itself is asymmetric. It is established that, unlike spin relaxation rate, contributions of different terms into magnetoconductivity are not additive. It is demonstrated that in the interval of electron densities under investigation (0.98-1.85)*10^(12) 1/cm^2 all three contribution are comparable and have to be taken into account to achieve a good agreement between the theory and experiment. The results obtained from comparison of the experiment and the theory have allowed us to determine what mechanisms dominate the spin relaxation in quantum wells and to improve the accuracy of determination of spin splitting parameters in A3B5 crystals and 2D structures.

cond-mat↗