Session MB: Condensed Matter Physics

Casimir-Polder Force Reversal with Metamaterials

A promising system design aiming to demonstrate Casimir-Polder force (CPF) reversal is proposed. The constraints when using naturally available materials in designing the system with air as an intermediate medium is resolved by using artificial electromagnetic materials. The parametric space in terms of the plate's magnetic and dielectric plasma frequencies, gap thickness and temperature is investigated. The parametric domain for achieving CPF reversal is obtained. Furthermore, a simple analytical expression for the CPF is derived. The analytical expression accurately describes the large and short distance asymptotics and allows extraction of important parameters such as lower and upper cutoff gap distances that define the repulsive force window. This study could possibly lead us to design of quantum levitation system, frictionless bio-fluid transport devices, etc.   

Generic Design of an Invisibility Device

A generic cloaking design based on realistic optical materials and existing nano-deposition techniques is proposed. A complete suppression of dipolar scattering is demonstrated by engineering cloaking systems encompassing two concentric shells. A transparency condition that does not depend on the object's geometrical and/or material properties using an expanded parametric space is proposed. The complete elimination of the system extinction cross-section is demonstrated in the quasi-static and full wave regime through use of non-dispersive and non-dissipative materials. Furthermore, a realistic shell designs based on composite metal/dielectric media is studied and the effect of loss and dispersion on the overall scattering cross-section is evaluated. It is shown that substantial reduction in the extinction cross-section (up to a factor of 10$^{4})$ can be achieved with pure dielectric materials in the optical and near-infrared spectral ranges. This study may provide a new direction for achieving optical invisibility without involvement of magnetism, i.e. metamaterials.   

MEAM potential for Al, Si, Mg, Cu, and Fe alloys

Modified Embedded Atom Method (MEAM) potential for Al, Si, Mg, Cu, and Fe alloys was developed as a combination of existing MEAM potentials for single elements. Pair parameters were constructed based on the structural and elastic properties of element pairs in the NaCl reference structure from ab-initio simulations, and then adjusted to reproduce heats of formation for binary compounds and defect formation energies. Some of the single element MEAM parameters were also improved to better match the generalized stacking fault curve. Validity and transferability of the new MEAM potential was tested by comparison with ab-initio simulations and experiments when available.   

Fermi-liquid properties of strongly imbalanced Fermi gases

Recent experiments [Schirotzek et al., PRL ${\bf 102}$, 230402 (2009)] involving highly imbalanced ultracold atomic gases have revealed so-called spin or Fermi polarons. These quasiparticles are composed of spinful atoms correlated with a ``cloud'' of atoms of opposite spin. These correlations lead to a renormalization of the free or bare atom's properties. Theoretically, these quasiparticles have been well described by a variational wave function consisting of a single impurity atom interacting with the remaining Fermi sea. Using diagrammatic many-body theory we extend these results and investigate the dependence of the polaron's Fermi liquid properties on finite temperature, as well as increased polaron density. Furthermore, we investigate instabilities of this normal Fermi liquid state, such as transitions to a superfluid or phase-separated state, as the temperature is lowered and/or the density of polarons is increased.   

Cyclotron Resonance in a High Mobility 2DEG

We have systematically studied the cyclotron resonance lifetimes of a high mobility ($\mu =3.4\times 10^{6}\mathrm{cm}^{2}\,\mathrm{V}^{-1}\,\mathrm{s}^{-1}$) two-dimensional electron gas as a function of temperature (0.38 K-80 K) using ultrafast terahertz spectroscopy. The cyclotron lifetime increases by $\sim$2x from 1.2 to 0.38 K, which results in a concomitant decrease in transmission amplitude due to the saturation effect. The differential amplitude of the time-delayed secondary pulse field is larger than the primary pulse and is not consistent with a Drude free carrier model.   

Electro-Optic Surface Effects in Rubidium Titanyl Phosphate (RTP)

The Laser Interferometer Gravitational Wave Observatory (LIGO) is a ground based gravitational wave telescope which utilizes a Michelson interferometer design to detect the differential changes in length caused by passing gravitational waves. Multiple resonant cavities were added to the interferometer design in order to increase power circulating in the interferometer, and thereby decrease noise. Resonant cavities, however, are very sensitive to alignment and hence can introduce a new source of noise into the interferometer output channel. As a risk reduction experiment, we developed an active cavity alignment system using textbook electro-optic RTP prisms which should theoretically be able to suppress noise into the high MHz regime. During initial testing of the prisms it was discovered that both the amount and direction of the deflection induced by an applied electric field vary strongly over the surface of the prism. This talk will describe the subsequent investigations into the nature of these inhomogeneities.