In underdoped cuprate superconductors, the Fermi surface undergoes a reconstruction that produces a small electron pocket, but whether there is another, as yet, undetected portion to the Fermi surface is unknown. Establishing the complete topology of the Fermi surface is key to identifying the mechanism responsible for its reconstruction. Here we report evidence for a second Fermi pocket in underdoped YBa2Cu3Oy, detected as a small quantum oscillation frequency in the thermoelectric response and in the c-axis resistance.

Using polarization-resolved photoluminescence spectroscopy, we investigate the breaking of valley degeneracy by an out-of-plane magnetic field in back-gated monolayer MoSe2 devices. We observe a linear splitting of -0.22meV/T between luminescence peak energies in σ+ and σ- emission for both neutral and charged excitons. The optical selection rules of monolayer MoSe2 couple the photon handedness to the exciton valley degree of freedom; so this splitting demonstrates valley degeneracy breaking.

We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ∼100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures.

We have developed methods for acquiring temporally and spatially resolved spectrograms of the velocity of sliding charge-density waves (CDWs), allowing unprecedented access to CDW dynamics. Complex transients arising from the interplay between elastic and plastic processes occur when the driving field direction is reversed. A transient spectral component due to shear elasticity can be unambiguously identified, and allows the most direct determination to date of the CDW's shear elastic modulus.

We employ reactive molecular-beam epitaxy to synthesize the metastable perovskite SrIrO3 and utilize in situ angle-resolved photoemission to reveal its electronic structure as an exotic narrow-band semimetal. We discover remarkably narrow bands which originate from a confluence of strong spin-orbit interactions, dimensionality, and both in- and out-of-plane IrO6 octahedral rotations.

We model the dynamics of condensation in a bimodal trap, consisting of a large reservoir region, and a tight "dimple" whose depth can be controlled. Experimental investigations have found that such dimple traps provide an efficient means of achieving condensation. In our kinetic equations, we include two- and three-body processes. The two-body processes populate the dimple, and lead to loss when one of the colliding atoms is ejected from the trap. The three-body processes produce heating and loss.

X-ray serial microcrystallography involves the collection and merging of frames of diffraction data from randomly oriented protein microcrystals. The number of diffracted X-rays in each frame is limited by radiation damage, and this number decreases with crystal size. The data in the frame are said to be sparse if too few X-rays are collected to determine the orientation of the microcrystal. It is commonly assumed that sparse crystal diffraction frames cannot be merged, thereby setting a lower limit to the size of microcrystals that may be merged with a given source fluence.

A one-pot synthesis approach is described to generate ordered mesoporous crystalline γ-alumina-carbon composites and ordered mesoporous crystalline γ-alumina materials via the combination of soft and hardlating chemistries using block copolymers as soft structure-directing agents. Periodically ordered alumina hybrid mesostructures were generated by self-assembly of a poly(isoprene)-block-poly(styrene)-block-poly(ethylene oxide) terpolymer, n-butanol and aluminum tri-sec-butoxide derived sols in organic solvents.

Flapping insect flight is a complex and beautiful phenomenon that relies on fast, active control mechanisms to counter aerodynamic instability. To directly investigate how freely flying Drosophila melanogaster control their body pitch angle against such instability, we perturbed them using impulsive mechanical torques and filmed their corrective maneuvers with high-speed video.

Atomically resolved spectroscopic imaging STM (SI-STM) has played a pivotal role in visualization of the electronic structure of cuprate high temperature superconductors. In both the d-wave superconducting (dSC) and the pseudogap (PG) phases of underdoped cuprates, two distinct types of electronic states are observed when using SI-STM.