This dissertation presents experimental studies of granular media using Nuclear Magnetic Resonance (NMR). Two different processes, vibrofluidization and gas fluidization of granular media, were investigated. In the first study, we measured the number density profiles and velocity distributions of the particles in a three-dimensional vibration system with pulse field gradient (PFG) NMR and magnetic resonance imaging (MRI) techniques. The experiments were repeated with three different values of N I and two different values of Γ, where N I is the number of layers of particles in the sample cell and Γ is the dimensionless acceleration of the vibration. We found the velocity distribution function is generally non-Gaussian except at the top of the sample. NMR data were fitted to a hydrodynamic theory, which successfully models the density and temperature profiles away from the vibrating container bottom. A temperature inversion near the free upper surface is observed, which is explained by the presence of a non-zero transport coefficient µ in inelastic systems. In the second study, we applied a fast 1D MRI technique to monitor the bubble motion in a fluidized bed. The measured bubble velocity is in excellent agreement with a model based on a potential flow theory. The number density profiles and the displacement distributions of particle were measured using PFG-NMR and MRI with various gas flow rates at different bed heights. We found no particle motion before bubbles are generated in the bed. The displacement distribution results imply that slugging phase is dominant at higher regions of the bed. The velocity distribution of convective particle flows in bubbling phase is fitted to a simple potential flow model, which shows reasonable agreement.

The work that is presented here is divided into two main sets of experiments. The first set of experiments deals with attempts to fabricate tunable third sound detectors. With different fabrications, the production of such thermometers results in transition temperatures quite different from those that can be obtained by the use of and manipulation of a single pure metal. We were able to reduce the transition temperature in a reasonably controlled manner by changing the Al/Au thickness ratio. The sensitivity of the bilayer detectors appear to be more uniform for various bias currents than the pure metal film detectors. This is advantageous when using the bias current to fine tune the transition temperature of a given detector. The purpose of the second set of experiments was to study helium films on substrates that contain a form of "ordered disorder", in this case a well ordered array of cylindrical pores. The main goals were to see what effects the pores had on the Kosterlitz-Thouless transition and to attempt to characterize the distribution in the size of the pores. This was done using quartz crystal microbalance and third sound techniques. As a major result, we found that the Kosterlitz-Thouless transition appears to be very robust with samples of various quality. The transition was observable in all of the samples studied and always appeared to scale with temperature as expected. The results that provided the least answers were the mass adsorption studies where helium was added to or removed from a quartz crystal microbalance. The samples demonstrated frequency shifts that were a function of helium film thickness. The effects occurred while adding and removing helium and they were observable at different temperatures. Even plain quartz crystals, which were found to be rougher than expected, showed large scale frequency shifts that suggest there is more happening on these substrates than expected. In some cases clear evidence of hysteresis was present and these samples are worth further investigation.

In my dissertation, I will discuss unconventional superfluid states of various bosonic systems and present benchmark calculations for phase diagrams. The method of study is based on quantum Monte Carlo simulations by the Worm algorithm. The two qualitatively different systems to be discussed in the thesis are: (i) superfluidity of lower dimensional objects, i.e dislocations and defects, embedded in solid structures both in optical lattices and in realistic systems such as 4He. (ii) the two-component Bose-Hubbard model. Besides the interesting phases and phase diagrams that they exhibit, bosonic optical lattice systems are also interesting for studies of quantum magnetism where under certain conditions they can be mapped onto various spin Hamiltonians. On the other hand, superfluid dislocations in 4He is an important and interesting subject for it’s relevance to supersolid behavior observed in solid 4 He. I will also present technical details of the path integral Monte Carlo and the Worm algorithm and generalization of the algorithm to the two-component bosonic systems.

This thesis presents data on experiments done with hcp 4He. The main focus is on the possibility of superfluidity inside solid 4He. The presence of superfluidity inside the solid should be manifested by a flow through the solid. The aim of these experiments was to search for a D.C. flow, characterize it and determine if the flow is due to superfluidity. A cell was designed that exploits the properties of helium in confined geometries to provide an interface between superfluid liquid helium, and hcp solid helium at pressures greater than the bulk melting curve. This interface allowed for a direct injection of atoms into the solid from the superfluid. With this cell, two different methods can be used to induce flow. In the first method, mass is injected directly into one side of the solid, while the pressure of the other side is monitored for a response. In the second method, flow is induced by changing the temperature of liquid reservoirs connected to the solid through porous Vycor glass. In addition to observing flow, it is also seen that a fountain pressure exists between the two liquid reservoirs connected to each other through the Vycor, and solid helium. Using this same design, the growth of solid helium was also studied at pressure higher than the bulk melting curve. Here, the solid cannot grow along a free surface, since off the melting curve the cell is supposed to be completely filled with solid. Near the melting curve, transients of 1–5 mK are seen in the temperature along with pressure drops [special characters omitted] 160 mbar. These transients are shown to probably be due to the solidification of metastable liquid regions imbedded in the solid. Off the melting curve, growth of the solid continues, and this growth is studied in the context of, “isochoric compressibility.”

We addressed the issue of ordering and self assembly in the context of flexible and semiflexible polyelectrolytes. The problems studied include the configurational and scattering properties of a single semiflexible polyelectrolyte in which we investigated the role of semiflexibility and electrostatics on the chain conformations. Effects of salt concentration and molecular weight have also been studied. Next, we extended the project to study orientational ordering induced by a collection of semiflexible polyelectrolytes with fixed molecular weight. We found rich phase behavior combining a first order Isotropic-Nematic phase transition and a second order critical point due to phase separation. Coupling of semiflexibility, electrostatics and their role on phase transition were investigated. Finally, we considered phase transitions in a solution of polydisperse semiflexible polymers, a problem which gives rise to interesting collective behavior. In the context of self assembly in charged system, we have also studied the process of micellization in a collection of polyelectrolytic diblock copolymers. The critical micelle concentration and its dependence on block molecular weights and salt concentration are discussed. Different problems have been studied with a combination of different analytical tools and numerical methods. The results of our research contrast with the existing literature and provide new insights in the field for future work.

This thesis presents measurements of collective modes and ultrafast carrier relaxation dynamics in charge-density-wave (CDW) conductors and colossal magnetoresistance (CMR) manganites. A femtosecond laser pump pulse excites a broad frequency spectrum of low-energy collective modes and electron-hole pairs thereby changing its optical properties. The low-energy collective excitations and quasiparticle relaxation and recombination processes are monitored by measuring the resulting photoinduced absorption as a function of probe pulse wavelength and time delay.;A general model was developed for the photogeneration and detection mechanism of collective modes based on light absorption in two-color pump-probe experiments. A broad spectrum of collective modes (phasons and amplitudons) with frequencies down to a few GHz is excited and propagates normal to the surface into the material. The dispersion of the long-wavelength phason and amplitudon can be measured by changing the probe wavelength.;The first pump-probe spectroscopy was performed from the ultraviolet to mid-infrared wavelength range to study low-frequency collective excitations, including temperature evolution, dispersion, damping, and anisotropy of amplitude mode and transverse phason in quasi-one dimensional CDW conductors, K 0.3MoO3 and K0.33MoO3 on ultrafast time scale. The transverse phason exhibits an acoustic-like dispersion relation in the frequency range from 5--40 GHz. The phason velocity is strongly anisotropic with a very weak temperature dependence. In contrast, the amplitude mode exhibits a weak (optic-like) dispersion relation with a frequency of 1.66 THz at 30 K.;The studies were extended to doped perovskite manganite thin films and single crystals. A low-energy collective mode is observed and discussed in terms of the opening of a pseudogap resulting from charge/orbital ordering phases. The softening of the collective mode is necessary to explain by combining a cooperative Jahn-Teller type distortion of the MnO6 octahedra with the collective mode. The quasiparticle dynamics in the vicinity of the metal-insulator transition is strongly affected by the presence of a pseudogap, phase separation and percolation, which are strongly dependent on temperature. A very long-lived relaxation process is observed due to a slow spin relaxation process. The dynamics of the spin system is further investigated in strained and unstrained thin films, which show a strong strain effect.

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Studies have shown that the dynamics of polymer supported films are strongly influenced by the specificities of the supporting surface. One key factor to the influence is the polymer-substrate interaction: the stronger this interaction is, the slower the dynamics become as the film thins. In the first part of this thesis, it is demonstrated that the dynamics of polymer films (measured by effective viscosity, ηeff) can be controlled by adjusting the polymer-substrate interactions. Polystyrene (PS) films supported by oxide-covered silicon was used as the model system. A combination of ultraviolet ozone (UVO) treatment of the polymer, and variable treatments of the substrate to change the concentrations of surface Si-OH groups, was used to adjust the polymer-substrate interaction. The ηeff of films was found to increase with the attractive interactions between the UVO-induced oxygenated groups in the polymer and the Si-OH on the substrate. Interesting implications about the dynamic properties of polymer surfaces were also drawn from the ηeff results. In the second part of this thesis, the supporting substrate was replaced by silicon covered by a soft, compliant layer of polymethylsiloxane (PDMS). Previous results showed that PS slips strongly on this surface. The ηeff of entangled PS on PDMS were measured and the films with Mw > ~393 kg/mol were found to slip in the rubbery elastic state, which is not discussed by prevailing theory. Based on the results, this study establishes for the first time that strongly slipping solid films obey the same linear relation as strongly slipping liquid films and a single friction coefficient is able to describe all the data. A microscopic model is proposed to explain the observations.

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