Physics

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The Physics department is committed to education and research in physics, the study of the fundamental universal laws that govern the behavior of matter and energy, and the exploration of the consequences and applications of those laws. Our department is widely known for its excellent teaching and student mentoring. Our department plays an important role in the university’s Core Curriculum. We have strong academic programs with several options for undergraduate physics majors, leading to the B.S. degree, as well as graduate curricula leading to the M.S. and Ph.D. degrees. Our research groups span a variety of fields within physics. Our principal concentrations are in Astrophysics, Relativity, Gravitation and Cosmology, Condensed Matter Physics, Lasers and Optics, Physics Education, Solar Physics, and the Space Science and Engineering Lab.

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Dielectric measurements of the proton-glass state in Rb0.65(NH4)0.35H2AsO4
(1988-09) Trybuła, Z.; Schmidt, V. Hugo; Drumheller, John E.; He, Di; Li, Zhouning
Dielectric measurements of the Rb1−x/emph>(NH4)xH2AsO4 (x=0.35) mixed crystals in the a and c tetragonal directions in the temperature range from 3 to 300 K are reported. Below Tg a dielectric dispersion of ε’(T) and ε’’(T) in the applied frequency range from 1 Hz to 30 kHz was observed. A small anisotropy of the proton-glass transition temperature Tg was detected, but we did not find the large anisotropy reported by J. Kim, N. Kim, and K. Lee [J. Phys. C 21, L-663 (1988)].
Cs 133 Nuclear Magnetic Resonance Study of One-Dimensional Fluctuations in CsH 2 PO 4 and Its Ferroelectric and Antiferroelectric Transitions at High Pressure
(1989-02) Schuele, Paul J.; Schmidt, V. Hugo
Pressure and temperature effects on the one dimensional (1D) and higher-dimensionality correlations associated with the ferroelectric and antiferroelectric phase transitions in cesium dihydrogen phosphate were studied by means of the Cs133 nuclear magnetic resonance (NMR) spin-lattice relaxation time T1. We measured T1 at 6.5 MHz at temperatures down to the ferroelectric (FE) Curie point TC at 1 bar and at 1.5 and 3.0 kbar, down to the triple point Tt=124.6 K at 3.3 kbar, and down to the antiferroelectric (AFE) Néel point TN at 3.6 kbar. With decreasing temperature, T1 first decreases exponentially due to 1D fluctuations associated with the Jb interactions in disordered hydrogen-bonded chains running along b. As the temperature falls further, T1 then decreases linearly as the Jc interaction between these chains in hydrogen-bonded planes comes into play. From these results and the known pressure derivatives of TC and TN, we calculated pressure dependences for Jb, Jc, and for the interplanar interaction Ja. At 3.3 kbar Ja changes sign, so the plane stacking becomes AFE instead of FE. Above 8.9 kbar, where Jc extrapolates to zero, a new AFE phase with a checkerboard arrangement of FE b chains is predicted.
17O NQR Study of the Antiferroelectric Phase Transition in TlH2PO4
(1988) Seliger, J.; Zagar, V.; Blinc, Robert; Schmidt, V. Hugo
The temperature dependence of the 1 7O NQR spectra in TlH2PO4 has been measured using a proton‐1 7 O nuclear quadrupole double resonance technique. The results show that the protons in the short one‐dimensionally linked O1–H1‐‐O1 and O2–H2‐‐O2hydrogen bonds are moving between two equilibrium sites above T c and freeze into one of the off‐center sites below T c . The protons in the asymmetric O3–H3‐‐O4hydrogen bonds are static and ordered above and below T c .
Comment on “dielectric study of the ferroelectric transition of KH2PO4”
(1976-08) Western, Arthur B.; Schmidt, V. Hugo
We reanalyze a.c. dielectric data taken by Eberhard and Horn for KH2PO4 near Tc, and obtain a much lower value of the critical bias field, near 300 V/cm in accord with results found by other workers.
Soft modes and proton tunneling in PbHPO4, squaric acid and KH2PO4, type ferroelectrics
(1984-01) Blinc, Robert; Schmidt, V. Hugo
It is pointed out that the huge observed differences in the soft mode frequencies of KH2PO4, PbHPO4, CsH2PO4 and squaric acid do not necessarily reflect a large difference in the proton 0—H———O tunneling frequencies but rather result from a difference in the short range correlations renormalizing the single proton O——H—O tunneling frequency.
Slater-senko model for CsH2PO4
(1984-04) Schmidt, V. Hugo
This model for CsH2PO4 considers all six Slater H2PO4 configurations and employs the Senko long-range interaction to obtain a ferroelectric transition above 0 K. Model predictions are compared with experimental results for susceptibility, spontaneous polarization, and correlation length.
EPR study of the symmetry breaking effect in ferroelectric cesium dihydrogen phosphate doped with Cr5+ ions
(1984-11) Waplak, S.; Schmidt, V. Hugo
The (PO4)3− units in a CsH2PO4 (CDP) crystal were replaced in a small fraction of sites by (CrO4)3− groups and the EPR of the Cr5+ center was investigated. Splitting of the EPR line appears at T∗c=245 K, 91 K higher that the ferroelectric transition temperature Tc=154 K. The electronic wave function of Cr5+ (3d1) is identified as dx2−y2. The dx2−y2 function couples with the near protons and the reorientation of this unit in the two possible configurations occurs in the paraelectric phase and breaks the symmetry far above Tc. The observed correlation time 10−9 sec and associated activation energy ΔU=0.215 eV are discussed.
PVF2 bimorphs as active elements in wind generators
(1983-11) Schmidt, V. Hugo; Klakken, M.; Darejeh, Hadi
The application to wind electric generation of bimorphs constructed of two sheets glued back-to-back of the piezoelectric polymer poly(vinylidene fluoride), or PVF2, is discussed. First, some fundamentals of piezoelectric behavior and of cantilever beam oscillations are reviewed. Then test results are presented for electrically driven PVF2 bimorphs oscillating in air and in vacuum, from which damping factors are derived. Next, two particular vertical axis wind generator designs are described employing such oscillating cantilever bimorphs which are forced into oscillation by the alternating direction of the wind forces acting on them during each rotor revolution. Wind tunnel test results for both designs are presented. Finally, the effect of possible improved polymer properties on generator output and cost is discussed.
Dielectric studies of critical and tricritical phenomena in kdp and RD
(1980-01) Schmidt, V. Hugo; Schnackenberg, P. T.; Western, Arthur B.; Baker, A. G.; Bacon, Charles R.; Crummett, W. P.
Our method of obtaining and analyzing dielectric data for KDP is reviewed, which demonstrated that KDP has a tricritical point between two and three kbar pressure. We also describe our method for obtaining the critical exponents r and d. Our experimental results for KDP are summarized. New results are presented for RDP which agree with the conclusion of others that its transition is of second order at ambient pressure.
Deuteration and pressure effects on landau free energy expansion coefficents in RbDXH2-xPO4
(1981-10) Schnackenberg, P. T.; Pipman, J.; Schmidt, V. Hugo; Tuthill, G. F.
Results are presented for undeuterated, 30% deuterated and 97% deuterated monocrystals of rubidium dihydrogen phosphate (RDP) for which the polarization was measured at various applied fields and accurately controlled temperatures within a degree above the ferroelectric transition temperature. The ferroelectric transition was found to be of second order at all deuterations. Some of these results were presented earlier.1–3

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