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Massless electrons behave relativistically 
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#1
Nov905, 07:41 PM

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PF Gold
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This is just one of a zoo of examples from condensed matter where relativistic forms manifest themselves via condensed matter phenomena.
http://physicsweb.org/articles/news/9/11/6/1 Just imagine. One could have a benchtop demo of QCD! Zz. 


#2
Nov905, 09:09 PM

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P: 1,135

American.... Electrons with zero restmass moving 100 million times faster through a solid state material than normal.....?! This must be signal speed. The explanation would be as follows. If the string of zeroes are electrons in the graphite and electron A kicks in resulting in electron B being kicked out at the other side then the speed of A to B would appear to be extremely high. A > 00000000000000000000000000000000000000000000  00000000000000000000000000000000000000000000 > B They somehow don't see the electrons in the graphite structure as mobile charge carriers. This coincides with the other bizarre remark that the conductivity remains even if there are "no mobile charge carriers in the graphite". Current without charge.... ?! Regards, Hans 


#3
Nov1005, 03:49 AM

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PF Gold
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The DIFFERENCE here from New Scientist etc. is that Physics Web is REPORTING a paper published elsewhere AND that they include the exact citation, something New Scientist and Sci Am are notorious for not consistently doing.
I read the Nature papers (there were TWO separate papers on the same subject in the same issue) and the News and Views on these two papers in the same issue, and the PhysicsWeb article is accurate! These results illustrates the bizzare behavior of what we mean as "charge transport" in 2D material. And I don't see anything wrong with "current without charge". After all, I have seen current without any bias voltage potential (Josephson current). The fact that these papers are producing unusual results is the reason why they got into Nature in the first place. Zz. 


#4
Nov1005, 09:43 AM

P: 576

Massless electrons behave relativistically
The Nature papers were an interesting read. There also was a mention in one of the papers that one or two theory groups had independently predicted the same behaviour so it seems that there's nothing wrong with physicsweb's credibility.



#5
Nov1005, 11:59 AM

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P: 1,135

things literally while the document repeatedly uses the word "fictitious". This speed of 1 million m/s per second comes from an effective calculation where [itex]E=m_cc_*^2[/itex] where [itex]c_* = 10^6 m/s[/itex] is called the "effective speed of light". This is something entirely different then saying that the electrons are actually moving with this speed. The two theory groups you mentioned had predicted the Quantum Hall Effects and not the "behavior" as suggested by physicsweb. Well, here are the papers. http://marcuslab.harvard.edu/jc/marcus0510.pdf http://arxiv.org/ftp/condmat/papers/0509/0509330.pdf Regards, Hans 


#6
Nov1005, 02:04 PM

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PF Gold
P: 29,239

I really don't see this as a problem, and certainly will not fault PhysicsWeb for using it especially the News and Views article in the same issue says the same thing. Zz. 


#7
Nov1505, 07:20 AM

P: 333

The "relativistic" here means that the energy dispersion relation of a quasiparticle follows [tex]E = c^{*} P[/tex], rather than the usual dispersion relation [tex]E = \frac{P^2}{2m_{eff}}[/tex], with P being the momentum of a quasiparticle and [tex]m_{eff}[/tex] the effective mass of the quasiparticle.
From this, the quasiparticle shows signs of effective relativistic phenomena, rather than the nonrelativistic effects shown by the quasiparticles experiencing the ordinary dispersion relation. 


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