Chemistry Reference
In-Depth Information
p
-pol HeI
12 K
q
e
-6
°
-8
°
-10
°
-12
°
-12.5
°
-13
°
-13.5
°
-14
°
-14.5
°
-15
°
-16
°
-18
°
E
F
-0.8
-0.6
-0.4
-0.2
0.0
0.2
Energy (eV)
Figure 6.2. Detail of the energy dispersion shown in Fig. 6.1. Energy is given
relative to
E
F
. Reprinted with permission from Segovia
et al.
, 1999. Copyright
(1999) by the Nature Publishing Group.
bands as depicted in Fig. 6.2. Both bands have different effective masses and have
been interpreted as originating from the separation of spin and charge, another
consequence of the electronic correlation in 1D systems. The spinon band would
correspond to the higher effective mass value (lower velocity and closer to
E
F
)
while the holon band would correspond to the lower effective mass value (higher
velocity). Using Eq. (1.34), even if it is only valid for weakly correlated systems,
with
k
F
4nm
−
1
, as derived from Fig. 6.1(b) and
a
∼
=
0
.
383 nm, we obtain that the
one-electron band is half occupied (
N
at
1), clearly indicating a metallic system.
The suppression of the photoemission signal at
E
F
in inorganic quasi-1D metals
has also been observed for several materials such as TaTe
4
, NbTe
4
and (NbSe
4
)
3
I
(Coluzza
et al.
, 1993), (TaSe
4
)
2
I and K
0
.
3
MoO
3
(Dardel
et al.
, 1991), Li
0
.
9
Mo
6
O
17
=
