Low-energy charge-density excitations in MgB2: Striking interplay between single-particle and collective behavior for large momenta.
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.
Cai
Y Q
YQ
National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan. cai@nsrrc.org.tw
Chow
P C
PC
Restrepo
O D
OD
Takano
Y
Y
Togano
K
K
Kito
H
H
Ishii
H
H
Chen
C C
CC
Liang
K S
KS
Chen
C T
CT
Tsuda
S
S
Shin
S
S
Kao
C C
CC
Ku
W
W
Eguiluz
A G
AG