In situ photoelectron spectra of an electron-beam irradiated C60 film
J. Onoe1*, T. Ito2, S. Kimura3, H. Shima4 and H. Yoshioka5
Research Laboratory for Nuclear Reactors and Department of Nuclear Engineering, Tokyo
Institute of Technology, Tokyo 152-8550, Japan2
Department of Materials, Physics and Energy Engineering, Nagoya University, Nagoya
464-8601, Japan
3
UVSOR Facility, Institute for Molecular Science, and School of Physical Sciences, The
Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
4
Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan
5
Department of Physics, Nara Women’s University, Nara 630-8506, Japan1

We have found that electron-beam (EB)irradiation of a C60 film gives rise to formation of apeanut-shaped
C60polymer
withmetallic
electron-transport properties in air at room
temperature [1]. The temperature dependence of thephoto-excited carriers lifetime for the peanut-shaped
polymer indicated the energy gap formation at below
50 K in a similar manner to the Peierls instability for
quasi-one-dimensional (1D) metallic materials suchas K0.3MO3 [2], thus suggesting that the polymer is a1D metal as illustrated in Fig. 1.
The 1D peanut-shaped polymer is fascinatingfrom a viewpoint of topology, because it has both
positive and negative Gaussian curvatures () lined
alternatively and periodically. As shown in Table 1,
this nanocarbon can be classified into a new -electron
conjugated carbon allotrope that is different fromgraphite ( = 0), fullerenes ( > 0), nanotubes ( = 0 at
body,  > 0 at cap edge), and hypothetical Mackay
crystal ( < 0). Accordingly, the 1D peanut-shaped
polymer is expected to exhibit physical and chemical
properties different from those of the conventional
-electron conjugated carbon materials.
We have recently examined the valence
photoelectron spectra of the polymer, using in situ
high-resolution ultraviolet photoelectron spectroscopy[3, 4], and observed the Tomonaga-Luttinger liquids(TLL) behavior as the direct evidence for 1D metaland obtained the TLL exponent (to be ca. 0.6 [5],which is somewhat larger than that of ca. 0.5 for 1D
metallic single-walled carbon nanotubes [6]. Using
the Schrodinger equation dealing with the motion offree particles on a curved surface modulated bypositive and negative Gaussian curvatures periodicallyand alternatively, we have first demonstrated that theincrease in the exponent value is caused by acurvature-induced effective potential that works forelectrons conducting along the curved surface [7].
To our best knowledge, the peanut-shaped C60
polymer is only an existed material with a negative
Gaussian curvature, whose electronic and opticalproperties are revealed. Thus we believe that thepresent system will open a new field of “quantumscience of condensed matters in Liemannian space”.

Fig. 1. Schematic illustration of one-dimensional
peanut-shaped C60 polymer.

Table 1. Classification of -electron conjugatedcarbon materials using Gaussian curvature.
Material
Gaussian curvature (K)Graphite0
Fullerenes>0Nanotubes
0 (body), > 0 (capped edge)
Mackay crystal<0Peanut-shaped polymer> 0, < 0*E-mail: jonoe@nr.titech.ac.jp[1] J. Onoe, T. Nakayama, M Aono, and T. Hara, Appl.
Phys. Letters 82 (2003) 595.
[2] Y. Toda, S. Ryuzaki, and J. Onoe, Appl. Phys.
Letters 92 (2008) 094102.
[3] J. Onoe et al., Phys. Rev. B 75 (2007) 233410.
[4] J. Onoe, T. Ito, and S. Kimura, J. Appl. Phys. 104(2008) 103706.
[5] T. Ito, J. Onoe, H. Shima, H. Yoshioka, and S.
Kimura, in preparation for submission.
[6] H. Ishii et al., Nature 426 (2003) 540.
[7] H. Shima, H. Yoshioka, and J. Onoe, Phys. Rev. B79 (2009) 201401 (R).