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Name (Title):
Canhua Liu (ICYS-MANA researcher)
Affiliation:
International Center for Young Scientists
(MANA), NIMS
Address:
1-1 Namiki, Tsukuba, Ibaraki 305-0875, Japan
Email: liu.canhua@nims.go.jp
Home Page: http://www.nims.go.jp/mana/members/icys_mana_researcher/c_liu
Presentation Title:
Phase modulation of quasi-one-dimensional charge-density waves induced by impurities
Abstract:
Low-dimensional materials
attract strong research interests
because of their fascinating
properties due to size reduction
and their promising for future
applications. Being cooled to a
critical temperature, pure lowdimensional
metals generally
undergo a Peierls transition,
which leads to the formation of
charge-density waves (CDW)
accompanied by a periodic
lattice distortion through
electron- phonon coupling.
Impurities play an important
part in determining both static
and dynamic CDW properties
through scattering electrons,
which modifies both phase and
amplitude of the CDW state. Especially, the phase pinning of CDW due to interaction with
impurities is a central concept for explaining various phenomena including nonlinear conductivity
and narrow band noise [1]. This issue, however, remains to be fully understood in spite of
enormous theoretical and experimental studies, partly because of the absence of direct observation
of the phase modulation in real space.
A self-organized array of In atomic wires, the Si(111)-4x1-In surface, provides the opportunity
of such direct observation as it exhibits the quasi-one-dimensional (Q1D) CDW transition [2,3],
as long as scanning tunneling microscopy (STM) is applied. By adding very small amount of Co
adsorbates (~0.02 ML) onto the In atomic wires and with STM performed at 80 K, we succeeded
in obtaining direct images of the phase and amplitude modulation of CDW due to the emergence
of Co adatoms. Concepts of phase pinning, phase slip and phase fluctuation are used to interpret
the observed phase modulation that shows a strong bias dependence. Our observation discovers
some new defect effects on the CDW that have not been reported yet.
References:
[1] G. Grüner, Rev. Mod. Phys. 60, 1129 (1988).
[2] H. W. Yeom, et al., Phys. Rev. Lett. 82, 4898 (1999).
[3] C. Liu, T. Uchihashi, and T. Nakayama, Phys. Rev. Lett. 101, 145104 (2008).
Poster Session PIR-6
Fig. (a) STM image of Co adatoms (bright protrusions) adsorbed Si(111)-
4x1-In surface taken at -1.2 V. (b) Line profiles taken of the lines indicated
in (a), showing CDW phase modulations as arrows indicate.
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