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Graphene lights up a fundamental truth Carbon

Graphene lights up a fundamental truth Carbon
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Jonathan Wood
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Available online 20 May 2008.
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RB(e`L!Du Measuring the values of fundamental constants that govern our universe, such as the speed of light, Planck's constant, or the charge of an electron, normally requires enormously specialized facilities and painstakingly controlled conditions. Yet it turns out that the fine structure constant a can be found by simply holding a sheet of graphene up to the light.
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-\ G&~k)@3M8zV Andre K. Geim and colleagues at the University of Manchester, UK, together with physicists at the University of Minho in Portugal, have shown that graphene absorbs a precise amount of incident white light that is determined solely by a [Nair et al., Sciencexpress (2008) doi: 10.1126/science.1156965].
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The fine structure constant describes the coupling between light and relativistic electrons, and so is normally more associated with the field of quantum electrodynamics than materials science. The most common way of measuring a is to look at the spectral lines of hydrogen that deviate from those expected in standard, nonrelativistic quantum physics, explains Geim. “Change this fine-tuned number by only a few percent and life would not be here because nuclear reactions in which carbon is generated from lighter elements in burning stars would be forbidden. No carbon means no life,” he adds.
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\ E[g,lW2j A single layer of graphene (central vertical stripe) stretched across the aperture absorbs π of the incident light, while a bilayer (to the right) absorbs twice that much.
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t"O'k6bv GV Although graphene is a sheet of carbon only one atom thick, it is found to absorb pa, or 2.3%, of light incident on it. This is a consequence of graphene's unique electronic structure, where electrons behave effectively like massless relativistic particles. Each extra layer of graphene absorbs another 2.3% of the light..F0mp`9b

f)sZ-u%q$Jr Obtaining large enough one-atom-thick graphene membranes for optical studies was crucial to observing this effect. The graphene sheets covered the submillimeter apertures in a metal scaffold to allow the optical measurements to be made.
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Although Geim and colleagues admit that obtaining values with metrological accuracy would be difficult, it is astonishing that a can be accessed in this facile way.3Ym!n2k"]_*ml
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“We were absolutely flabbergasted when realized that such a fundamental effect could be measured in such a simple way. One can have a glimpse of the very foundations of our universe just looking through graphene,” Geim remarks

graphene 现在很火热。