Physics Commons^™

Superfluorescence Polarization: Signature Of Collisional Redistribution, A. Kumarakrishnan, S. Chudasama, Xianming Han

Xianming Han

We have studied effects of magnetic sublevel degeneracy on the polarization of superfluorescent pulses generated on the Ca 4s4p1P1–3d4s1D2 transition at 5.5μm. These pulses were generated from a cell of length 50 cm by optically pumping calcium vapor on the 4s21S0–4s4p1P1 transition in the presence of Ar gas. The axis of ellipticity of superfluorescence (SF) polarization is oriented parallel to the axis of the pump-laser polarization at large detunings, and undergoes an abrupt rotation through 90° for detunings close to resonance. The distribution of populations in the magnetic sublevels of the 1P1 state can be estimated using a simple model …

The Effects Of Strain And Vacancies On The Electric And Vibrational Properties Of Ferroelectric Batio3 From First-Principles, Aldo Serge Michael Raeliarijaona

Graduate Theses and Dissertations

The studies of ferroelectricity (FE) are of technological significance because of the multitude of applicable properties that ferroelectric materials exhibit. The mastery, and control of these properties necessitate the knowledge of the fundamental physics governing these insulating materials.

In this dissertation I present the results of first-principles investigations of the behavior of the fundamental ferroelectric properties under strain, and in the presence of vacancies. In the first part I introduce the important FE properties, their common behavior, and their numerous valuable applications. Following this background on FEs, a review of theoretical methods is presented with topics such as: Density Functional …

Shifting The Quantum-Classical Boundary: Theory And Experiment For Statistically Classical Optical Fields, Xiao-Feng Qian, Bethany Little, John C. Howell, Joseph H. Eberly

Mathematics, Physics, and Computer Science Faculty Articles and Research

The growing recognition that entanglement is not exclusively a quantum property, and does not even originate with Schrödinger’s famous remark about it [Proc. Cambridge Philos. Soc. 31, 555 (1935)], prompts the examination of its role in marking the quantum-classical boundary. We have done this by subjecting correlations of classical optical fields to new Bell-analysis experiments and report here values of the Bell parameter greater than ℬ=2.54. This is many standard deviations outside the limit ℬ=2 established by the Clauser–Horne–Shimony–Holt Bell inequality [Phys. Rev. Lett. 23, 880 (1969)], in agreement with our theoretical classical prediction, and not far from the Tsirelson …

Room Temperature Optical Anisotropy Of A Lamno3 Thin-Film Induced By Ultra-Short Pulse Laser, Purevdorj Munkhbaatar, Zsolt Marton, Baatarchuluun Tsermaa, Woo Seok Choi, Sung S. Ambrose Seo, Jin Seung Kim, Naoyuki Nakagawa, Harold Y. Hwang, Ho Nyung Lee, Kim Myung-Whun

Physics and Astronomy Faculty Publications

We observed ultra-short laser pulse-induced transient optical anisotropy in a LaMnO₃ thin film. The anisotropy was induced by laser pulse irradiation with a fluence of less than 0.1 mJ/cm² at room temperature. The transmittance and reflectance showed strong dependence on the polarization states of the pulses. For parallel and perpendicular polarization states, there exists a difference of approximately 0.2% for transmittance and 0.05% for reflectance at 0.3 ps after the irradiation with a pump pulse, respectively. The theoretical values for optical transmittance and reflectance with an assumption of an orbital ordering of 3d e_g electrons in …

Gravitational Correction To Vacuum Polarization, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We consider the gravitational correction to (electronic) vacuum polarization in the presence of a gravitational background field. The Dirac propagators for the virtual fermions are modified to include the leading gravitational correction (potential term) which corresponds to a coordinate-dependent fermion mass. The mass term is assumed to be uniform over a length scale commensurate with the virtual electron-positron pair. The on-mass shell renormalization condition ensures that the gravitational correction vanishes on the mass shell of the photon, i.e., the speed of light is unaffected by the quantum field theoretical loop correction, in full agreement with the equivalence principle. Nontrivial corrections …

Electric Control Of Spin Injection Into A Ferroelectric Semiconductor, Xiaohui Liu, John D. Burton, M. Ye. Zhuravlev, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Electric-field control of spin-dependent properties has become one of the most attractive phenomena in modern materials research due to the promise of new device functionalities. One of the paradigms in this approach is to electrically toggle the spin polarization of carriers injected into a semiconductor using ferroelectric polarization as a control parameter. Using first-principles density-functional calculations, we explore the effect of ferroelectric polarization of electron-doped BaTiO₃ (n-BaTiO₃) on the spin-polarized transmission across the SrRuO₃/n-BaTiO₃(001) interface. Our study reveals that, in this system, the interface transmission is negatively spin polarized …

One-Loop Dominance In The Imaginary Part Of The Polarizability: Application To Blackbody And Noncontact Van Der Waals Friction, Ulrich D. Jentschura, Grzegorz Lach, Maarten Dekieviet, Krzysztof Pachucki

Physics Faculty Research & Creative Works

Phenomenologically important quantum dissipative processes include blackbody friction (an atom absorbs counterpropagating blueshifted photons and spontaneously emits them in all directions, losing kinetic energy) and noncontact van der Waals friction (in the vicinity of a dielectric surface, the mirror charges of the constituent particles inside the surface experience drag, slowing the atom). The theoretical predictions for these processes are modified upon a rigorous quantum electrodynamic treatment, which shows that the one-loop "correction" yields the dominant contribution to the off-resonant, gauge-invariant, imaginary part of the atom's polarizability at room temperature, for typical atom-surface interactions. The tree-level contribution to the polarizability dominates …

Peppo: Using A Polarized Electron Beam To Produce Polarized Positrons, A. Adeyemi, G.L Gueye, P.A. Adderly, M. L. Stutzman, M. M. Ali, H. Areti, J. F. Benesch, L. S. Cardman, J. Clark, S. Covert, S. Golge, C. Hyde

Physics Faculty Publications

An experiment demonstrating a new method for producing polarized positrons has been performed at the CEBAF accelerator at Jefferson Laboratory. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁺/e⁻ pairs originating from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a 1.0 mm tungsten pair-production target. This paper describes preliminary results of measurements using an 8.2 MeV/c electron beam with polarization 84% to generate positrons in the range of 3.1 to 6.2 MeV/c with polarization as high as ∼80%.

Constructing The Quantum Steering Ellipsoid Using State Measurement Of Biphotons, Carter Vanderbilt

Senior Projects Spring 2015

This paper investigates a recently discovered geometric representation of two-qubit states, the Quantum Steering Ellipsoid, by exploring quantum state measurements on mixtures of polarization-entangled photons produced using spontaneous parametric down conversion (SPDC). Measurements of the second photon of a mixed biphoton system that are conditioned on observations of the first photon demonstrate all possible Bloch Vectors that the second photon can be collapsed to by way of ''steering,'' which is only possible due to the nonlocal nature of entangled systems. This paper examines methods to experimentally verify the Quantum Steering Ellipsoid as a geometric classification of quantum states.