Magnetoresistivity Modulated Response in Bichromatic Microwave Irradiated Two Dimensional Electron Systems

We analyze the effect of bichromatic microwave irradiation on the magnetoresistivity of a two dimensional electron system. We follow the model of microwave driven Larmor orbits in a regime where two different microwave lights with different frequencies are illuminating the sample ($w_{1}$ and $w_{2}$). Our calculated results demonstrate that now the electronic orbit centers are driven by the superposition of two harmonic oscillatory movements with the frequencies of the microwave sources. As a result the magnetoresisitivity response presents modulated pulses in the amplitude with a frequency of $\frac{w_{1}-w_{2}}{2}$, whereas the main response oscillates with $\frac{w_{1}+w_{2}}{2}$.Comment: 4 pages, 3 figures Accepted in Applied Physics Letter

From zero resistance states to absolute negative conductivity in microwave irradiated 2D electron systems

Recent experimental results regarding a 2D electron gas subjected to microwave radiation reveal that magnetoresistivity, apart from presenting oscillations and zero resistance states, can evolve to negative values at minima. In other words, the current can evolve from flowing with no dissipation, to flow in the opposite direction of the dc bias applied. Here we present a theoretical model in which the existence of radiation-induced absolute negative conductivity is analyzed. Our model explains the transition from zero resistance states to absolute negative conductivity in terms of multiphoton assisted electron scattering due to charged impurities. It shows as well, how this transition can be driven by tuning microwave frequency and intensity. Then it opens the possibility of controlling the electron Larmor orbits dynamics (magnetoconductivity) in microwave driven nanodevices. The analysis of zero resistance states is therefore promising because new optical and transport properties in nanodevices will be expected.Comment: 5 pages and 4 figure

Role of Balloon Guide Catheter in Modern Endovascular Thrombectomy

Proximal flow control achieved with a balloon guide catheter (BGC) during endovascular treatment of acute ischemic stroke is reviewed in this article. In clinical practice, BGCs offer a multi-faceted approach for clot retrieval by creating proximal flow arrest, reducing embolic burden, and shortening procedure time. Evaluation of frontline thrombectomy procedures with BGCs revealed advantages of combined use over the conventional guide catheter (CGC), notably in the significant reduction of distal emboli to both the affected and previously unaffected territories. Recently, new measures of early and complete reperfusion at first thrombectomy pass have been identified as independent predictors of improved outcomes, which were consistently demonstrated with use of BGC as a safe and effective option to minimize number of passes during intervention. Prior randomized controlled trials reported the positive correlation between BGC-treated patients and a lower risk of mortality as well as shortened procedure time. While BGC use is more common in stent retriever-mediated mechanical thrombectomy, preliminary data has shown the potential benefit of device application during contact aspiration thrombectomy to achieve successful recanalization. However, the question of which major endovascular strategy reigns superior as a frontline remains to be answered. Along with clinical case assessments, BGC performance during in-vitro simulation was analyzed to further understand mechanisms for optimization of thrombectomy technique

Pairing in the quantum Hall system

We find an analogy between the single skyrmion state in the quantum Hall system and the BCS superconducting state and address that the quantum mechanical origin of the skyrmion is electronic pairing. The skyrmion phase is found to be unstable for magnetic fields above the critical field $B_{c}(T)$ at temperature $T$, which is well represented by the relation $B_c(T)/B_{c}(0) \approx {[1-(T/T_c)^3]}^{1/2}$.Comment: revtex, two figures, to appear in Phys. Rev. B (Rapid Communications

Transport through a Strongly Correlated Quantum-Dot with Fano Interference

We present the transport properties of a strongly correlated quantum dot attached to two leads with a side coupled non-interacting quantum dot. Transport properties are analyzed using the slave boson mean field theory which is reliable in the zero temperature and low bias regime. It is found that the transport properties are determined by the interplay of two fundamental physical phenomena,i.e. the Kondo effects and the Fano interference. The linear conductance will depart from the unitary limit and the zero bias anomaly will be suppressed in the presence of interdot coupling. The zero bias shot noise Fano factor increases with the interdot coupling and tends to the Poisson value. The shot noise Fano factor shows a non-monotonic behavior as a function of the interdot coupling for various side dot energy levels

Density functional theory of the phase diagram of maximum density droplets in two-dimensional quantum dots in a magnetic field

We present a density-functional theory (DFT) approach to the study of the phase diagram of the maximum density droplet (MDD) in two-dimensional quantum dots in a magnetic field. Within the lowest Landau level (LLL) approximation, analytical expressions are derived for the values of the parameters $N$ (number of electrons) and $B$ (magnetic field) at which the transition from the MDD to a ``reconstructed'' phase takes place. The results are then compared with those of full Kohn-Sham calculations, giving thus information about both correlation and Landau level mixing effects. Our results are also contrasted with those of Hartree-Fock (HF) calculations, showing that DFT predicts a more compact reconstructed edge, which is closer to the result of exact diagonalizations in the LLL.Comment: ReVTeX 3.

Correlation effects in a quantum dot at high magnetic fields

We investigate the effects of electron correlations on the ground state energy and the chemical potential of a droplet confined by a parabolic potential at high magnetic fields. We demonstrate the importance of correlations in estimating the transition field at which the first edge reconstruction of the maximum density droplet occurs in the spin polarized regime.Comment: 11 pages (revtex) 3 postscript figures are included at the end of the tex file. To appear in Phys. Rev.

Devil's Staircase in Magnetoresistance of a Periodic Array of Scatterers

The nonlinear response to an external electric field is studied for classical non-interacting charged particles under the influence of a uniform magnetic field, a periodic potential, and an effective friction force. We find numerical and analytical evidence that the ratio of transversal to longitudinal resistance forms a Devil's staircase. The staircase is attributed to the dynamical phenomenon of mode-locking.Comment: two-column 4 pages, 5 figure

Symmetry-breaking skyrmion states in fractional quantum Hall systems

We calculate in an analyical fashion the energies and net spins of skyrmions in fractional quantum Hall systems, based on the suggestion that skyrmion states are spontaneously $L_Z$ and $S_Z$ symmetry-breaking states. The quasihole-skyrmion state with a charge $-e/3$ around $\nu$ = 1/3, where the ground state is known as a spin-polarized ferromagnetic state, is found to exist even in high magnetic fields up to about 7 T for GaAs samples.Comment: There is conceptual change. To appear in Phys. Rev.