-
J M Chen,
C K Chen,
T L Chou,
I Jarrige,
H Ishii,
K T Lu,
Y Q Cai,
K S Liang,
J M Lee,
S W Huang,
T J Yang,
C C Shen,
R S Liu,
J Y Lin,
H T Jeng, C C Kao
Applied Physics Letters 01/2007; 91(5). · 3.84 Impact Factor
-
Y Q Cai,
P C Chow,
O D Restrepo,
Y Takano,
K Togano,
H Kito,
H Ishii,
C C Chen,
K S Liang,
C T Chen,
S Tsuda,
S Shin, C C Kao,
W Ku,
A G Eguiluz
[show abstract]
[hide abstract]
ABSTRACT: A sharp feature in the charge-density excitation spectra of single-crystal MgB2, displaying a remarkable cosinelike, periodic energy dispersion with momentum transfer (q) along the c* axis, has been observed for the first time by high-resolution nonresonant inelastic x-ray scattering (NIXS). Time-dependent density-functional theory calculations show that the physics underlying the NIXS data is strong coupling between single-particle and collective degrees of freedom, mediated by large crystal local-field effects. As a result, the small-q collective mode residing in the single-particle excitation gap of the B pi bands reappears periodically in higher Brillouin zones. The NIXS data thus embody a novel signature of the layered electronic structure of MgB2.
Physical Review Letters 11/2006; 97(17):176402. · 7.37 Impact Factor
-
Y Q Cai,
H-K Mao,
P C Chow,
J S Tse,
Y Ma,
S Patchkovskii,
J F Shu,
V Struzhkin,
R J Hemley,
H Ishii,
C C Chen,
I Jarrige,
C T Chen,
S R Shieh,
E P Huang, C C Kao
[show abstract]
[hide abstract]
ABSTRACT: The near K-edge structure of oxygen in liquid water and ices III, II, and IX at 0.25 GPa and several low temperatures down to 4 K has been studied using inelastic x-ray scattering at 9884.7 eV with a total energy resolution of 305 and 175 meV. A marked decrease of the preedge intensity from the liquid phase and ice III to ices II and IX is attributed to ordering of the hydrogen bonds in the proton-ordered lattice of the latter phases. Density functional theory calculations including the influence of the Madelung potential of the ice IX crystal correctly account for the remaining preedge feature. Furthermore, we obtain spectroscopic evidence suggesting a possible new phase of ice at temperatures between 4 and 50 K.
Physical Review Letters 02/2005; 94(2):025502. · 7.37 Impact Factor
-
AIP Conf. Proc.; 01/2004
-
[show abstract]
[hide abstract]
ABSTRACT: High-pressure X-ray near-edge absorption measurements have been performed on thallium rhenium oxide (TlReO4) up to 10.86 GPa at room temperature and in a diamond-anvil cell. At 10 GPa, TlReO4 undergoes a large volume collapse and a striking optical transition, changing from transparent to opaque. A model has been proposed by Jayaraman et al. that the high-pressure phase transition is associated with a charge transfer from the thallium to rhenium atom; Tl1+(Re7+O4)−1 → Tl3+(Re5+O4)−3 and an accompanying truly octahedral coordination of the rhenium atom with respect to the surrounding oxygen cage. In this article, we find a significant broadening of 1.5 eV of the white-line feature at the rhenium L3(2p3/2 → 5d) absorption-edge above this transition, and no evidence for the proposed valence change.
High Pressure Research 12/2003; 23(4):471-476. · 0.78 Impact Factor
-
Physical Review Letters 01/1999; 83(16):3343-3343. · 7.37 Impact Factor
-
Physical Review Letters 01/1999; 83(20):4101-4104. · 7.37 Impact Factor
