Scanning optical homodyne detection of high-frequency picoscale resonances in cantilever and tuning fork sensors

Higher harmonic modes in nanoscale silicon cantilevers and microscale quartz tuning forks are detected and characterized using a custom scanning optical homodyne interferometer. Capable of both mass and force sensing, these resonators exhibit high-frequency harmonic motion content with picometer-scale amplitudes detected in a 2.5 MHz bandwidth, driven by ambient thermal radiation. Quartz tuning forks additionally display both in-plane and out-of-plane harmonics. The first six electronically detected resonances are matched to optically detected and mapped fork eigenmodes. Mass sensing experiments utilizing higher tuning fork modes indicate >6x sensitivity enhancement over fundamental mode operation.Comment: 3 pages, 3 figures, submitted to Applied Physics Letter

Polarization immunity of magnetoresistivity response under Microwave excitation

We analyze theoretically the dependence of the microwave polarization sate and sense on the magnetoresistivity response of two-dimensional electron systems. Linear and circular polarization have been considered with different senses and directions. We discuss the polarization dependence of the longitudinal magnetoresistivity and propose an explanation for the experimentally observed polarization immunity, i.e., resistivity oscillations and zero resistance state regions are unaffected by the sense of circular polarization or by the direction of microwave electric field.Comment: 4 pages and 1 figur

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.

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

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.

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

Analysis of neurodegenerative Mendelian genes in clinically diagnosed Alzheimer disease

Alzheimer disease (AD), Frontotemporal lobar degeneration (FTD), Amyotrophic lateral sclerosis (ALS) and Parkinson disease (PD) have a certain degree of clinical, pathological and molecular overlap. Previous studies indicate that causative mutations in AD and FTD/ALS genes can be found in clinical familial AD. We examined the presence of causative and low frequency coding variants in the AD, FTD, ALS and PD Mendelian genes, in over 450 families with clinical history of AD and over 11,710 sporadic cases and cognitive normal participants from North America. Known pathogenic mutations were found in 1.05% of the sporadic cases, in 0.69% of the cognitively normal participants and in 4.22% of the families. A trend towards enrichment, albeit non-significant, was observed for most AD, FTD and PD genes. Only PSEN1 and PINK1 showed consistent association with AD cases when we used ExAC as the control population. These results suggest that current study designs may contain heterogeneity and contamination of the control population, and that current statistical methods for the discovery of novel genes with real pathogenic variants in complex late onset diseases may be inadequate or underpowered to identify genes carrying pathogenic mutations

Design, Analysis and Empirical Researches for Solar Heat Collecting System based on Flat Mirrors Combination

There has been a dramatic increase of research on energy production using solar energy. This research aims to examine development of concentrating solar collector that is related to mid-high solar energy field. Although the use of dish type solar thermal system has been common in the existing high-efficiency collector technology, several problems have been raised. In order to solve these issues, the frame has been designed as flat plate type with Fresnel lens and the structural stability has been proved by analysis. Furthermore, the experiment that checks collectorrsquos temperature has been performed for the correct works of the stirling engine