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taozhikai

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[资源] science最新一篇光子准晶体

Quasicrystals are aperiodic structures with rotational
symmetries forbidden to conventional periodic crystals,
examples of which can be found in aluminium alloys,
polymers, and even ancient Islamic art. Here, we present
direct experimental observation of disorder-enhanced
wave transport in quasicrystals, which contrasts directly
with the characteristic suppression of transport by
disorder. Our experiments are carried out in photonic
quasicrystals, where we find that increasing disorder
leads to enhanced expansion of the beam propagating
through the medium. By further increasing the disorder,
we observe that the beam progresses through a regime of
diffusive-like transport until it finally transitions to
Anderson localization and the suppression of transport.
We study this fundamental phenomenon, and elucidate its
origins by relating it to the basic properties of quasicrystalline
media in the presence of disorder.
Anderson localization (1), a fundamental concept in solidstate
physics, describes how introducing disorder can
transform a conducting crystal into an insulator. This
prediction and subsequent experiments have shown that
generally disorder works to arrest transport, in periodic
systems (crystals) containing disorder (2–4) as well as in fully
random potentials (5–9). However, some systems still pose
fundamental challenges to this concept, most notably,
quasicrystals. Quasicrystals (QCs) (10, 11) constitute an
intermediate phase between fully periodic and fully
disordered media: they do not have a unit cell and do not
exhibit translation symmetry, but nevertheless possess noncrystallographic
rotational symmetry, long-range order and
display Bragg diffraction. Although many of the properties of
QCs are now well understood, some fundamental questions
remain. Perhaps one of the most intriguing questions related
to QCs has to do with transport. Opposite to crystals
containing disorder, which exhibit Anderson localization, it
has been suggested that disorder can enhance transport in
QCs (12, 13). Indirect experiments indicated that indeed, in
some regime, increasing disorder could enhance transport

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