The spin-split incompressible edge states within empirical Hartree approximation at intermediately large Hall samples

A self-consistent Thomas-Fermi-Poisson based calculation scheme is used to achieve spin resolved incompressible strips (ISs). The effect of exchange and correlation is incorporated by an empirically induced g factor. A local version of the Ohm's law describes the imposed fixed current, where the discrepancies of this model are resolved by a relevant spatial averaging process. The longitudinal resistance is obtained as a function of the perpendicular (strong) magnetic field at filling factor one and two plateaus. Interrelation between the ISs and the longitudinal zeros is explicitly shown.Comment: EP2DS-17 Proceedings, 6 Pages, 2 Figure

Correlated electron tunneling through two separate quantum dot systems with strong capacitive interdot coupling

A system consisting of two independently contacted quantum dots with strong electrostatic interaction shows interdot Coulomb blockade when the dots are weakly tunnel coupled to their leads. It is studied experimentally how the blockade can be overcome by correlated tunneling when tunnel coupling to the leads increases. The experimental results are compared with numerical renormalization group calculations using predefined (measured) parameters. Our results indicate Kondo correlations due to the electrostatic interaction in this double quantum dot system.Comment: 5 pages, 3 figures, published in Phys. Rev. Lett. Oct. 30t

Layer-by-layer formation of oligoelectrolyte multilayers: a combined experimental and computational study

For the first time, the combination of experimental preparation and results of fully atomistic simulations of an oligoelectrolyte multilayer (OEM) made of poly(diallyl dimethyl ammonium chloride)/poly(styrene sulfonate sodium salt) (PDADMAC/PSS) is presented. The layer-by-layer growth was carried out by dipping silica substrates in oligoelectrolyte solutions and was modeled by means of atomistic molecular dynamics simulations with a protocol that mimics the experimental procedure up to the assembly of four layers. Measurements of OEM thickness, surface roughness and amount of adsorbed oligoelectrolyte chains obtained from both approaches are compared. A good agreement between simulated and experimental results was found, with some deviations due to intrinsic limitations of both methods. However, the combination of information extracted from simulations to support the analysis of experimental data can overcome such restrictions and improve the interpretation of experimental results. On the other hand, processes dominated by slower kinetics, like the destabilization of adsorbed layers upon equilibration with the surrounding environment, are out of reach for the simulation modeling approach, but they can be investigated by monitoring in situ the oligoelectrolyte adsorption during the assembly process. This demonstrates how the synergistic use of simulation and experiments improves the knowledge of OEM properties down to the molecular scale

Composite fermions in periodic and random antidot lattices

The longitudinal and Hall magnetoresistance of random and periodic arrays of artificial scatterers, imposed on a high-mobility two-dimensional electron gas, were investigated in the vicinity of Landau level filling factor ν=1/2. In periodic arrays, commensurability effects between the period of the antidot array and the cyclotron radius of composite fermions are observed. In addition, the Hall resistance shows a deviation from the anticipated linear dependence, reminiscent of quenching around zero magnetic field. Both effects are absent for random antidot lattices. The relative amplitude of the geometric resonances for opposite signs of the effective magnetic field and its dependence on illumination illustrate enhanced soft wall effects for composite fermions

The Cyclotron Spin-Flip Mode as the Lowest-Energy Excitation of Unpolarized Integer Quantum Hall States

The cyclotron spin-flip modes of spin unpolarized integer quantum Hall states ($\nu =2,4$) have been studied with inelastic light scattering. The energy of these modes is significantly smaller compared to the bare cyclotron gap. Second order exchange corrections are held responsible for a negative energy contribution and render these modes the lowest energy excitations of unpolarized integer quantum Hall states.Comment: Published: Phys. Rev. B 72, 073304 (2005

Periodic Structures with Rashba Interaction in Magnetic Field

We analyze the behaviour of a system of particles living on a periodic crystal in the presence of a magnetic field B. This can be done by involving a periodic potential U(x) and the Rashba interaction of coupling constant k_{so}. By resorting the corresponding spectrum, we explicitly determine the band structures and the Bloch spinors. These allow us to discuss the system symmetries in terms of the polarizations where they are shown to be broken. The dynamical spin will be studied by calculating different quantities. In the limits: k_{so} and U(x)=0, we analyze again the system by deriving different results. Considering the strong $B$ case, we obtain an interesting result that is the conservation of the polarizations. Analyzing the critical point \lambda_{k,\sigma}=\pm\sq{1\over 2}, we show that the Hilbert space associated to the spectrum in z-direction has a zero mode energy similar to that of massless Dirac fermions in graphene. Finally, we give the resulting energy spectrum when B=0 and U(x) is arbitrary.Comment: 24 pages, references added, misprints corrected. Version to appear in JP

Precision of Quantization of the Hall Conductivity in a Sample of Finite Size: Power Law

A microscopic calculation of the conductivity in the integer quantum Hall effect (IQHE) regime is carried out. The problem of precision of quantization is analyzed for samples of finite size. It is demonstrated that the precision of quantization shows a power-law dependence on the sample size. A new scaling parameter describing a dependence of this kind is introduced. It is also demonstrated that the precision of quantization linearly depends on the ratio between the amplitude of the chaotic potential and the cyclotron energy. The results obtained are compared with the magnetotransport measurements in mesoscopic samples.Comment: 5 pages, 4 figure