College of Arts and Sciences

I will describe the adaptation of electro-optic (EO) polymer technology to terahertz (THz) generation and detection. The generation of wide bandwidth THz radiation (mid-IR to far-IR) with a smooth frequency response using low power laser sources is very desirable for scientific and technological applications such as vibrational analysis of biomolecules, medical imaging, non-contact electrical measurements, and homeland security. EO polymers have the potential to make a significant impact in this field due to their large nonlinearities, ease of processing, and low dispersion from the optical to the THz region. I will describe the fabrication of 100-300 m thick polymer films with electrooptic coefficients greater than 50 pm/V and report their use as emitters and sensors of THz radiation.

Continue reading… Optical rectification and electro-optic sampling in the THz regime using electro-optic polymers – Michael Hayden

Unambiguous evidence for novel neutrino properties has recently been obtained from observations of solar and reactor neutrinos. Combined with previous solar neutrino experiments the results from SNO and KamLAND are evidence for neutrino oscillation. The Sudbury Neutrino Observatory (SNO) studies neutrinos from the 8B decay in the Sun to search for neutrino flavor change. SNO’s unique measurement of all neutrino flavors has provided model- independent evidence for the flavor transformation of solar neutrinos. Its results imply that neutrinos have mass. This observation explains the long-standing Solar Neutrino Problem, the deficit of the observed electron solar neutrino flux compared to solar model predictions.

Continue reading… Evidence for Neutrino Oscillation and Massive Neutrinos: The Resolution of the Solar Neutrino Problem at SNO and KamLAND – Karsten Heeger, Michelson Postdoctoral Prize Lecture

It is possible to drive magnetic ordering temperatures in certain metallic magnets to zero temperature by means of applied field, pressure, or compositional variation. We have been using neutron scattering measurements to study the development of dynamic and spatial correlations near one such T=0 antiferromagnetic transition in the heavy fermion system CeRu2Ge2, doped with Fe. We establish that the dynamical susceptibility is controlled equally by energy, absolute temperature, and wave vector magnitude, measured relative to the propagation wave vector of the parent finite temperature antiferromagnet. Unusually, critical slowing down affects a very broad range of wave vectors, suggesting that the quantum critical point is caused by the collapse of the moment magnitude,

Continue reading… Quantum Criticality near Zero Temperature Phase Transitions – Meigan Aronson

Laser polarization of 3He and 129Xe generates nuclear spin polarizations 100,000 times greater than Boltzmann equilibrium at 2 Tesla and 300 K. The advent of these hyperpolarized gases has led to a wealth of research and applications in atomic and materials physics, chemistry, and medicine. After a brief introduction to magnetic resonance and hyperpolarization, the physics of optical pumping and spin exchange in the production of hyperpolarized gases will be introduced and discussed. Several novel applications, including nuclear polarization transfer and diffusion imaging in normal and diseased human lungs, will be detailed. New research on the discovery of ferromagnetism in glass spin-exchange cells will also be treated,

Continue reading… Magnetic Resonance of Hyperpolarized Noble Gases – Jason C. Lea Woods

The presentation is to draw a picture of Optical Coherence Tomography (OCT), which has tremendous applications in biomedical research and clinic disease diagnosis, with a great potential commercial market. The fundamental principle of the OCT is to use the theory of the coherent optics or the electromagnetic waves. The focus of the OCT study is to get high resolution, high contrast and high imaging speed. I would like to discuss how to improve the performance of OCT, and also to demonstrate a few kinds of OCT images and real time movies collected by the OCT devices developed in the group at Case Western Reserve University.

Continue reading… The Development of Optical Coherence Tomography at CASE and the Optical Related Bio-Images – Zhilin Hu

The ongoing revolution in information technology drives advances in the ability to synthesize, manipulate, and probe nanometer-size materials. Among the new developments, single-quantum-level tunneling spectroscopy emerges as a powerful tool to study the electronic structure of individual metal nanograins. I will present a microscopic theory of electron tunneling in ultra-small aluminum grains, which helps understanding tunneling spectroscopy experiments. The observed high density of resonances and the asymmetry of the tunneling spectra agains voltage-bias reversal can be understood within the new theory. I will also show that the local electrostatic environment of metal grains significantly change the spectroscopy in the nanoscopic regime.

Continue reading… Theory of electron tunneling in ultra-small aluminum grains – Gustavo A. Narvaez

The general phenomenology of multilayer epitaxial growth and erosion on square (001) and rectangular (110) symmetry crystal surfaces is discussed. Recently observed transitions between two kinds of ripple states on (110) surfaces are studied within a unified model. Predictions are made about several novel interface states, intervening via consecutive transitions between two rippled states on (110) surfaces. Surface morphology, coarsening dynamics, and far-from-equilibrium transitions on (001) surface are studied. Intermediary interface states with many-sided pyramids on (001) surface are predicted and characterized.

Continue reading… Structure and Dynamics of Interfaces in the MBE Growth on (110) and (100) Crystal Surfaces – Artem Lewandowsky

Manipulating electron spin is one of the central problems in the growing field of semiconductor spintronics. This is of critical importance for quantum computing and information processing. Here I discuss the “optical initialization” and “optical read out” of the spin of an electron localized in a quantum dot [1]. We suggest using the combined effects of -optical pulses and transverse magnetic field for the optical pumping of the electron spin in QDs and the initialization of single spin Q-bit. The calculation shows that ~100% spin polarization can be reached as a result of several repetitions of this procedure. For “read out” of the single electron spin we suggest using a resonance fluorescence of trions excited resonantly by circularly polarized light,

Continue reading… Electron Spin Manipulation in Semiconductor Nanostructures – Alexander Efros

Magnetic resonance imaging, widely utilized for obtaining excellent anatomical images of soft tissue, has increasingly been applied to the study of brain function. By manipulating image acquisition, information about parameters such as perfusion, diffusion, neural activity, blood volume, and blood oxygenation can be obtained. Combining this functional contrast with fast, high-resolution imaging techniques creates a flexible tool for probing neural networks and their interactions.

Continue reading… Visualizing Functional Connections in the Brain with Magnetic Resonance Imaging – Shella Keilholz

Continue reading… The use of antibodies coupled to quantum-dot filled microspheres – Maureen McEnery

When liquids are cooled rapidly, particles can no longer move freely and the liquid becomes a glass. Above the glass temperature Tg, relaxation in supercooled liquids obeys the Vogel-Fulcher law, τ ∼ exp[-E/(T-T0)] with T0 < Tg. The physical origin of this behavior is still largely unknown. We review some theoretical models for glassy relaxation. We then examine elastic properties of supercooled liquids and explore the role of stress in glassy relaxation.

Continue reading… On the Origin of Soft-Vibrational Modes in Glass-Forming Liquids – Ulrich Zurcher

In general, the physical systems are quite complex in nature. Our approximate knowledge of the complicated interactions in these systems manifests itself by a randomization of various generators of the dynamics. The operators associated with wave dynamics e.g Hamiltonian, electromagnetic waves in a microwave cavity, or signals in a brain etc. can therefore be modeled by random matrices. The choice of a suitable random matrix model of a complex system is very sensitive to the nature of its complexity. The statistical spectral analysis of various complex systems requires, therefore, a thorough probing of a wide range of random matrix ensembles which is not an easy task.

Continue reading… Level Statistics of Complex Systems: A Random Matrix Approach – Pragya Shukla

I will describe the goals and activities of our Center for Oxide-Semiconductor Materials for Quantum Computation (COSMQC, http://cosmqc.net). In our proposed architecture, quantum information is stored in electron spins, which form the basis for qubits. Spin-polarized electrons are created in Ge/Si quantum dots using optical orientation. Fast optical gating of Zeeman (one-qubit) and Heisenberg (two-qubit) interactions proceeds via optical rectification in an epitaxial ferroelectric. This approach takes advantages of native excitations and interactions in the solid state: (i) electron spins, charges, and photons for initialization and readout, (ii) quantum-mechanical (Heisenberg, Zeeman, spin-orbit) and classical (magnetic, electric, optical intensity) couplings for quantum gating,

Continue reading… Oxide-semiconductor materials for quantum computation – Jeremy Levy

Electrons on liquid helium have been proposed as qubits [1], using excited Rydberg states [2] as the |0> and |1> quantum states. This requires the trapping of single electrons in quantum wells, the excitation of Rydberg states using millimetric microwaves and the detection of the quantum states of the electrons. Progress towards these objectives will be described. In particular, we have detected individual trapped electrons on a pool of helium, 0.8 micron deep and 5 micron diameter, using a superconducting single-electron transistor (SET). Electrons on the helium surface induce a positive charge in the SET island and a phase shift in the Coulomb blockade oscillations (CBO) in the SET source-drain current.

Continue reading… Counting electrons on helium with a single electron transistor – Mike Lea

A Mutual Composite Fermion (MCF) picture is proposed to explain the interlayer coherent incompressible phase in bilayer Quantum Hall systems at total filling factor νT=ν1+ν2 =1. There are gapped quasi-particles (QP) and quasi-holes (QH) excitations with total fractional charges ±ν1 and ±ν2. The total fractional charges are evenly distributed between the two layers. The QP and QH are asymptotically free even at T=0 . In contrast to previous claims, there is no finite temperature phase transition. Our results are contrasted with previous results from different pictures. Experimental implications are given.

Continue reading… Is there a finite temperature phase transitions in bilayer quantum Hall system ? – Jinwu Ye

Narrow gap nitride semiconductors have shown significant promise for a wide range of applications, including long-wavelength light-emitters, high performance electronic devices, and high efficiency solar cells. In the case of GaAsN, a consequence of the large N-As size difference is a predicted limited miscibility on the anion sublattice, which often leads to the formation of GaN-rich nanostructures [1-2]. Dilute GaAsN alloys are typically achieved using low growth temperatures, which enable N incorporation without GaN surface conversion. In addition, conflicting results have been reported regarding the mechanism of N incorporation, and recent optical studies have suggested that the shear deformation potential and/or the binary elastic constants may have an unusual composition dependence [3].

Continue reading… Structure and Properties of Narrow Gap Nitride Films – Rachel Goldman

Continue reading… Exploiting self-assembly to create polar organic thin films with piezoelectric, pyroelectric, and second order nonlinear optical response – Daniel Dyer

Electronic structure calculations are used to study the magnetic properties of MnN and Mn3N2. The magnetic moments originate primarily from the Mn t2g orbitals and are in good agreement with neutron diffraction measurements. The ground state is found to be antiferromagnetically ordered along [001] planes in agreement with experiment. By mapping the energy differences between various spin configurations to a Heisenberg model we find that the dominant interactions in MnN are a second nearest neighbor ferromagnetic interaction due to double exchange via nitrogen and a nearest neighbor antiferromagnetic direct exchange interaction about 4 times smaller than the second nearest neighbor interaction.

Continue reading… Magnetic interactions in metallic anti-ferromagnetic manganese nitride compounds – Walter Lambrecht