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Posted: October 30, 2008

Conductance plateaus of graphene p-n junctions discovered

(Nanowerk News) Recently, Sun Qingfeng with the Lab for Condensed Matter Theory and Materials Computation, Chinese Academy of Sciences (CAS) Institute of Physics made an intensive study on the electron transport through graphene p-n junctions in cooperation with Long Wen with the Capital Normal University and Wang Jian from the University of Hong Kong. Their research paper entitled with "Disorder-Induced Enhancement of Transport through Graphene p-n Junctions" was published on the 16th issue of Physical Review Letters on October 17th.
Graphene is the name given to a flat single layer of carbon atoms densely packed into a two-dimensional honeycomb lattice and also a basic building block for graphitic materials of all other dimensionalities. Back to the last century, it was already revealed that the unique band structure of graphene could lead to many peculiar properties. Recently, the successful fabrication of graphene in laboratory brings new interests among scientists.
In their research under the joint support from the National Natural Science Foundation of China and CAS, Prof. Sun and his colleagues investigated the conductance of clean and disordered graphene p-n junctions by using the Landauer-bŁttiker formalism combined with the nonequilibrium Green function method.
They find that the conductance is quite small for the clean samples under a perpendicular magnetic field, while in the presence of disorders it can be dramatically enhanced. And at a suitable range of disorders, some conductance plateaus emerge, the values of which exhibits at 1e2/h, 3/2 e2/h, 5/3 e2/h, 3 e2/h, etc. The lowest conductance plateaus can sustain for a very broad range of disorder strength (about 2 orders of magnitude), but the existence of high plateaus depends on system parameters and sometimes cannot be formed at all. These research results are in agreement with a recent experiment.
Source: Chinese Academy of Sciences