arXiv subjects

D. Wu

Publications and source records attributed to D. Wu.

111 records · Page 7Linked to original sources

arXiv2004

Metamagnetic Transition in Na$_{0.85}$CoO$_2$ Single Crystals

We report the magnetization, specific heat and transport measurements of high quality Na$_{0.85}$CoO$_2$ single crystals in applied magnetic fields up to 14T. In high temperatures, the system is in a paramagnetic phase. It undergoes a magnetic phase transition below about 20K. When the field is applied along the c-axis, the measurement data of magnetization, specific heat and magnetoresistance reveal a metamagnetic transition from an antiferromagnetic state to a quasi-ferromagnetic state at about 8T in low temperatures. However, no transition is observed in the magnetization measurements up to 14T when the field is applied perpendicular to the c-axis. The low temperature magnetic phase diagram of Na$_{0.85}$CoO$_2$ is determined.

cond-mat.supr-con↗

arXiv2004

Infrared probe of the electronic structure and charge dynamics in Na$_{0.7}$CoO$_2$

We present measurements of the optical spectra on Na$_{0.7}$CoO$_2$ single crystals. The optical conductivity shows two broad interband transition peaks at 1.6 eV and 3.2 eV, and a weak midinfrared peak at 0.4 eV. The intraband response of conducting carriers is different from that of a simple Drude metal. A peak at low but finite frequency is observed, which shifts to higher frequencies with increasing temperature, even though the dc resistivity is metallic. We discussed the origin of the interband transitions and the low-frequency charge dynamics based on the results of band structure calculations and quasiparticle behavior observed in ARPES experiment.

cond-mat.supr-con↗

arXiv1994

On Measuring $CP$ Violation in Neutral $B$-meson Decays at the $Υ(4S)$ Resonance

Within the standard model we carry out an analysis of $CP$-violating observables in neutral $B$-meson decays at the $Υ(4S)$ resonance. Both time-dependent and time-integrated $CP$ asymmetries are calculated, without special approximations, to meet various possible measurements at symmetric and asymmetric $e^{+}e^{-}$ $B$ factories. We show two ways to distinguish between direct and indirect $CP$-violating effects in the $CP$-eigenstate channels such as $B^{0}_{d}/\bar{B}^{0}_{d}\rightarrow π^{+}π^{-}$ and $π^{0} K_{S}$. Reliable knowledge of the Cabibbo-Kobayashi-Maskawa phase and angles can in principle be extracted from measurements of some non-$CP$-eigenstate channels, e.g. $B^{0}_{d}/\bar{B}^{0}_{d}\rightarrow D^{\pm}π^{\mp}$ and $\stackrel{(-)}{D}$$^{(*)0}K_{S}$, even in the presence of significant final-state interactions.

hep-ph↗