Diamond anvil cell techniques are now well established and powerful methods for measuring materials properties to very high pressure. However, high pressure resistivity measurements are challenging because the electrical contacts attached to the sample have to survive to extreme stress conditions. Until recently, experiments in a diamond anvil cell were mostly limited to non-hydrostatic or quasihydrostatic pressure media other than inert gases. We

Recently discovered materials called three-dimensional topological insulators constitute examples of symmetry protected topological states in the absence of applied magnetic fields and cryogenic temperatures. A hallmark characteristic of these non-magnetic bulk insulators is their protected metallic Dirac fermion-like surface states. Electrons in these surface states are spin polarized with their spins governed by their momentum, resulting in a helical

We present temperature dependent magnetic neutron diffraction measurements on Ba(Fe1−xCox)2As2 for x=0.039, 0.022, and 0.021 as-grown single crystals. Our investigations probe the behavior near the magnetic tricritical point in the (x,T) plane, xtr≈0.022, as well as systematically exploring the character of the magnetic phase transition across a range of doping values. All samples show long-range antiferromagnetic order that may be described

Magnetic correlations in isovalently doped Ba(Fe1-xRux)2As2 (x=0.25, Tc=14.5  K; x=0.35, Tc=20  K) are studied by elastic and inelastic neutron scattering techniques. A relatively large superconducting spin gap accompanied by a weak resonance mode is observed in the superconducting state in both samples. In the normal state, the magnetic excitation intensity is dramatically reduced with increasing Ru doping toward the optimally doped regime.

We present high-pressure diamond-anvil cell synchrotron x-ray, resistivity, and ac-susceptibility measurements on the electron-doped cuprate Pr2-xCexCuO4 to much higher pressures than previously reported. At 2.72 GPa between 88 and 98% of the superconducting T phase of the optimally doped Pr1.85Ce0.15CuO4 transforms into the insulating phase T . With application of pressure, the T phase becomes more insulating, so we present here an example of electron