Chemistry Reference
In-Depth Information
30 K
70 K
k = k
F
0=E
F
0.4
0.0
Binding Energy (eV)
Figure 6.7. High-resolution ARUPS spectra measured at
k
F
(
h
2 eV) above
(70 K) and below (30 K) the Peierls transition. The solid line spectrum corresponds
to
E
F
, as determined for a silver film. Note that the spectrum follows the shape
given by Eq. (1.27). Reprinted with permission from F. Zwick, D. Jerome, G.
Margaritondo, M. Onellion, J. Voit and M. Grioni,
Physical Review Letters
,
81
,
2974 (1998). Copyright (1998) by the American Physical Society.
ω
=
21
.
2nm
−
1
. Using again Eq. (1.34), as for the previously dis-
occurs at
k
F
=
2
.
5
±
0
.
cussed Au/Si(111)-(5
×
1) case, for
N
at
=
=
0
.
59 and
b
=
0
.
382 nm we obtain
4nm
−
1
, in perfect agreement with the experiment.
2
Thus
k
F
=
2
.
can be evaluated
from ARUPS experiments.
High-resolution spectra taken at
k
F
and at 70 and 30 K, just above and below the
CDW transition, respectively, are shown in Fig. 6.7. At 70 K the intensity at
E
F
is
vanishingly small, characteristic of 1D systems. Taking the midpoint of the leading
edge as an indicator, a pseudogap energy of
120 meV is derived. Between 70 and
30 K the leading edge of the spectrum shifts by 20 meV to higher binding energies,
indicating the opening of a gap, the Peierls gap, of
∼
∼
40 meV.
2
The
a
parameter from Eq. (1.34) corresponds to the stacking parameter
b
from TTF-TCNQ.
