College of Arts and Sciences

Quasi-one-dimensional free-standing fluid structures are not often found in nature, but may be formed by any material that can overcome capillary instability. Once this instability is suppressed, long filaments, with a length-to-diameter ratio greater than �, may form. Liquid crystals are an extraordinary system that can form free-standing fluid filaments with length-to-diameter ratios exceeding 7000. Buckling instabilities in freestanding liquid crystal filaments formed from bent-core liquid crystals in the B7 phase may be induced in a variety of ways, e.g. by acoustical or electrical vibration. However, this talk will focus on instabilities induced by compressing the filament, as well as those from a mechanical or thermal rupture.

Continue reading… Buckling Instabilities and Recoil Dynamics in Free-Standing Liquid Crystal Filaments – Tanya Ostapenko

Continue reading… Quantum Phase Transitions in Magnets – Ribhu Kaul

Liquid bridges were flown aboard a Boeing 727-200 aircraft in a series of parabolic arcs that produced multiple periods of microgravity. During the microgravity portion of each arc, g_eff , the effective total body acceleration due to external forces became negligibly small so that cylindrical liquid bridges could be suspended across two coaxial support posts. Near the bottom of each arc, g_eff slowly increased to a maximum of 1.84g, causing the liquid bridges to deform and in some cases collapse. Although the physics of liquid bridges subject to varying total body force is well-established and has been analyzed extensively both theoretically and experimentally,

Continue reading… Thank You for Flying the ‘Vomit Comet’: Using Parabolic Flights to Examine Quantitatively the Stability of Liquid Bridges Under Varying Total Body Force – Greg DiLisi

V2O5 is a layered material with chains within the layer. I will discuss how this is manifested in its electronic band structure. The quasiparticle self-consistent GW method in this material strongly overestimates the band gap. The main reasons for this are examined and found to be a lattice polarization contribution to the screening of the electron-electron interaction. This is related to the large LO/TO phonon splittings in this material. Changes in band structure and phonons between bulk and monolayer will be discussed.

Continue reading… V2O5, a Strongly Correlated 2D System with 1D Aspects – Walter Lambrecht

Rapidly advancing high-performance super computers such as “Blue Waters” allow calculating properties of increasingly complex materials with unprecedented accuracy. In order to fully take advantage of leadership-class machines and to accurately describe modern materials, codes need to scale well on hundreds of thousands of processors. This talk focuses on electronic excitations and their ultrafast attosecond dynamics that are notoriously difficult to capture due to the quantum-mechanical electron-electron interaction. Being omnipresent in electronic and optical materials, an accurate description is a crucial factor for computational design of materials for technological applications.

It will be outlined how cutting-edge first-principles techniques based on many-body perturbation theory accomplish predictive theoretical spectroscopy of electronic excitations e.g.

Continue reading… Predictive First-principles Simulations of Excited Electrons and Ultrafast Electron-ion Dynamics in Complex Materials – Andre Schleife

Experimental and theoretical study of Cs and Eu atoms adsorption on graphene on Ir(111) will be presented [1,2]. Graphene on Ir(111) surface is an interesting system because graphene has almost pristine electronic structure in it due to its weak bonding character to iridum surface. The bonding is almost exclusively of the van der Waals type. However adding Cs or Eu atoms graphene gets doped and and nature of binding changes – especially in the case when the atoms intercalate. Density Functional Theory calculations with standard semilocal functionals (GGA) – fail to reproduce experimental findings even qualitatively. Only when the newly developed nonlocal correlation functional is used (vdW-DF) which includes van der Waals interactions,

Continue reading… Graphene on Ir(111), Adsorption and Intercalation of Cs and Eu Atoms – Pedrag Lazic

APS March Meeting 2015 graduate student talks

Jiayuan Miao: Molecular-dynamics study of the Case-II diffusion of methanol in PMMA

Sukrit Sucharitakul: Field effect vs. Hall mobility in back-gated multilayered InSe FETs

Nicholas J. Goble: Effects of structural phase transitions on the interface of perovskite oxides

Bin Liu: Ultrastrong exciton-photon coupling in single and coupled organic microcavities

Ittipon Fongkaew: Electric field and spin-orbit coupling effects on the band structure of monolayer WSe2

Continue reading… March Meeting Preview Talks – Graduate Students

The combination of solubility, coded pairing and adjustable flexibility make DNA a unique polymer for designing highly-controlled self-assembled complex nanostructures and novel materials. The same tools can be exploited to produce DNA-based systems enabling the exploration of challenging topics in soft matter physics. In the talk I will exemplify this approach by describing experiments and results in which DNA assembly was used to study living polymerization, liquid crystal ordering, the templating of chemical reactions, and phase behavior and gelation transition of low-valence colloidal particles.

Continue reading… Exploring Soft Matter with DNA – Tomasso Bellini

SiO4 is a common building block of many materials, both crystalline such as quartz, silicates and zeolites, and amorphous, such as silica. Although intuitively one would think that SiO4 is an achiral perfect tetrahedron, in the vast majority of silicon-oxide based materials, that tetrahedron is of lower symmetry, to the degree of being chiral. Discussion of the chirality of SiO4 and its manifestation in crystalline and amorphous materials, will be the main focus of this lecture. Specific topics to be covered include the induction of chirality in silicas; the contribution of randomness to the emergence of chirality; the chirality of zeolites and silicates;

Continue reading… The Chirality of SiO4 in Materials – David Avnir

Graphene, a monoatomic layer of carbon, is perhaps the simplest and most easily available material where electrons behave as massless Dirac particles. Apart from the many promising technological applications, the study of graphene (and other layered materials) has opened a number of interesting theoretical questions: the microscopic crystalline structure requires an additional degree of freedom (the pseudo spin) that gives rise to effects such as the Klein paradox or Veselago electron lenses. The spin-orbit interaction (SOI) in materials arises from intrinsic lack of inversion symmetry in the lattice structure or from external or interfacial fields that break spatial symmetries. Although SOI is weak in natural graphene,

Continue reading… Spin-dependent Scattering in Graphene: Electronic Birefringence and Kondo Transitions – Sergio Ulloa