Effects of Pressure on the Electronic and Structural Properties of LaOFeAs

We studied the pressure effects on the electronic and structural properties of LaOFeAs by first-principles calculations. For the anti-ferromagnetic (AFM) phase with stripe- like aligned Fe spins, the electronic density of states at the Fermi level (N (EF)) slightly descends first with increasing applied pressure, then bounces up with further increasing pressure (or decreasing volume), and reaches its maximum at ~ 29.2 GPa with the volume ~ 80% of the ambient pressure value (V0). At this volume (V = 0.8V0), the LaOFeAs crystal undergoes a structural phase transition from the orthorhombic structure to the tetragonal one, which is accompanied by the disappearance of the long-ranged AFM order.Comment: 20 pages, 5 figure

Universal linear-temperature resistivity: possible quantum diffusion transport in strongly correlated superconductors

The strongly correlated electron fluids in high temperature cuprate superconductors demonstrate an anomalous linear temperature ($T$) dependent resistivity behavior, which persists to a wide temperature range without exhibiting saturation. As cooling down, those electron fluids lose the resistivity and condense into the superfluid. However, the origin of the linear-$T$ resistivity behavior and its relationship to the strongly correlated superconductivity remain a mystery. Here we report a universal relation $d\rho/dT=(\mu_0k_B/\hbar)\lambda^2_L$, which bridges the slope of the linear-$T$-dependent resistivity ($d\rho/dT$) to the London penetration depth $\lambda_L$ at zero temperature among cuprate superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ and heavy fermion superconductors CeCoIn$_5$, where $\mu_0$ is vacuum permeability, $k_B$ is the Boltzmann constant and $\hbar$ is the reduced Planck constant. We extend this scaling relation to different systems and found that it holds for other cuprate, pnictide and heavy fermion superconductors as well, regardless of the significant differences in the strength of electronic correlations, transport directions, and doping levels. Our analysis suggests that the scaling relation in strongly correlated superconductors could be described as a hydrodynamic diffusive transport, with the diffusion coefficient ($D$) approaching the quantum limit $D\sim\hbar/m^*$, where $m^*$ is the quasi-particle effective mass.Comment: 8 pages, 2 figures, 1 tabl

Gene editing: A new step and a new direction toward finding a cure for Duchenne muscular dystrophy (DMD)

AbstractDuchenne muscular dystrophy (DMD) is a progressive muscle degenerative disease affecting one out of 3500 male births. Patients usually succumb to the disease by age 25. It has been shown that skipping exons of the DMD gene that contain disease-causing mutations from the pre-mRNA can result in a shortened, but functional, dystrophin protein that could bring clinical benefits to patients. A recent breakthrough has been reported in Science by three groups who demonstrated that genetically deleting exon 23 by gene editing can restore the expression of dystrophin (albeit a shortened version) and improve the muscle function in a mouse model of DMD