Topological insulators in three spatial dimensions are known to possess a precise bulk-boundary correspondence, in that there is a one-to-one correspondence between the five classes characterized by bulk topological invariants and Dirac Hamiltonians on the boundary with symmetry protected zero modes. This holographic characterization of topological insulators is studied in two dimensions. Dirac Hamiltonians on the one-dimensional edge are classified according to the discrete symmetries of time reversal, particle hole, and chirality, extending a previous classification in two dimensions.

We demonstrate a large enhancement in the interaction of light with graphene through coupling with localized modes in a photonic crystal nanocavity. Spectroscopic studies show that a single atomic layer of graphene reduces the cavity reflection by more than a factor of one hundred, while also sharply reducing the cavity quality factor. The strong interaction allows for cavity-enhanced Raman spectroscopy on subwavelength regions of a graphene sample. A coupled-mode theory model matches experimental observations and indicates significantly increased light absorption in the graphene layer.

This work examines the effect of perturbing the position of bound CO 2 in the active site of human carbonic anhydrase II (HCA II) on catalysis. Variants of HCA II in which Val143 was replaced with hydrophobic residues Ile, Leu, and Ala were examined. The efficiency of catalysis in the hydration of CO2 for these variants was characterized by 18O exchange mass spectrometry, and their structures were determined by X-ray crystallography at 1.7-1.5 Å resolution.

We describe a tunable low-energy photon source consisting of a laser-driven xenon plasma lamp coupled to a Czerny-Turner monochromator. The combined tunability, brightness, and narrow spectral bandwidth make this light source useful in laboratory-based high-resolution photoemission spectroscopy experiments. The source supplies photons with energies up to ∼7 eV, delivering under typical conditions >1012 ph/s within a 10 meV spectral bandwidth, which is comparable to helium plasma lamps and many synchrotron beamlines.

The semiconductor ZnGeN2 was grown by a vapor-liquid-solid mechanism. Ordering of the Zn-Ge sublattice with growth temperature and Zn partial pressure was investigated by powder X-ray diffraction and was found to be sensitive to the growth temperature and insensitive, over the range explored, to the Zn and NH3 partial pressures. The degree of disorder on the cation sublattice was observed to correlate with the suppression of predicted Raman peaks and the emergence of phonon density-of-states features. © 2013 Materials Research Society.

Recent observations of broken symmetries have partly demystified the pseudogap phase. Here we review evidence for long-range intra-unit-cell (IUC) nematic order and its unexpectedly strong coupling to the phase of the fluctuating stripes in the pseudogap states of underdoped Bi 2Sr 2CaCu 2O 8+δ.

Using a novel SQUID-based torsional oscillator (TO) technique to achieve increased sensitivity and dynamic range, we studied TO's containing solid 4He. Below ∼250 mK, the TO resonance frequency f increases and its dissipation D passes through a maximum as first reported by Kim and Chan. To achieve unbiased analysis of such 4He rotational dynamics, we implemented a new approach based upon the generalized rotational susceptibility χ 4He -1(ω, T ).

We review the current state of efforts to use resonant soft X-ray scattering (RSXS), which is an elastic, momentum-resolved, valence band probe of strongly correlated electron systems, to study stripe-like phenomena in copper-oxide superconductors and related materials. We review the historical progress including RSXS studies of Wigner crystallization in spin ladder materials, stripe order in 214-phase nickelates, 214-phase cuprates, and other systems.

Recent advances in computational methods have made realistic large-scale simulations of animal locomotion possible. This has resulted in numerous mathematical and computational studies of animal movement through fluids and over substrates with the purpose of better understanding organisms' performance and improving the design of vehicles moving through air and water and on land. This work has also motivated the development of improved numerical methods and modeling techniques for animal locomotion that is characterized by the interactions of fluids, substrates, and structures.

Vortices in a type-II superconductor form a lattice structure that melts when the thermal displacement of the vortices is an appreciable fraction of the distance between vortices. In an anisotropic high-T c superconductor, such as YBa 2Cu 3O y, the magnetic field value where this melting occurs can be much lower than the mean-field critical field H c2. We examine this melting transition in YBa 2Cu 3O y with oxygen content y from 6.45 to 6.92, and we perform a quantitative analysis of this transition in the cuprates by fitting the data to a theory of vortex-lattice melting.