Nov 10, 2021 | Control of graphene trough sound waves
Original source LAQUINTA COLUMNA:
DIRECTO NOCTURNO DE LA QUINTA COLUMNA - PROGRAMA 178 - Nov 9, 2021: https://odysee.com/@laquintacolumna:8/DIRECTONOCTURNODELAQUINTACOLUMNA-PROGRAMA178-:7
Control del grafeno mediante sonido: https://www.investigacionyciencia.es/revistas/investigacion-y-ciencia/el-origen-de-la-tecnologa-709/control-del-grafeno-mediante-sonido-15378
Controlling graphene with sound
A theoretical study suggests the possibility of using mechanical waves to govern the behaviour of electrons in this two-dimensional material. The finding could find applications in electronics and in the design of smart materials.
In recent years, single-atom-thick (two-dimensional) materials have sparked a revolution in nanotechnology. They first came to the fore in 2004, when Andre Geim and Konstantin Novoselov of the University of Manchester discovered graphene, a material made of carbon monolayers, which won them the 2010 Nobel Prize in physics. Over time, this family has expanded to include silicon (silicon monolayers), phosphorene (phosphorus monolayers) and two-dimensional transition metal dichalcogenides (MoS2, NiSe2, etc.). All of them exhibit electronic, optical, chemical and mechanical properties of great interest. In particular, it is believed that they could replace silicon in electronics in the future. The ability to control the behaviour of electrons in these materials is of fundamental interest.
Graphene has been dubbed the "wonder material": it is the best known conductor of electricity and heat, and combines the lightness of graphite with the strength of diamond. This resistance to mechanical deformation is explained by the strength of the bonds between its carbon atoms, which are arranged in a hexagonal honeycomb-like structure. A typical solid material can stretch up to 3 percent of its length. Graphene, on the other hand, stretches up to 23 per cent. Moreover, this deformation is elastic: when the force that causes it disappears, it returns to its original shape. On the other hand, its length increases proportionally to the deformation force; in other words, it behaves like a spring, a mechanical system that physicists know very well.
The deformations of graphene generate all sorts of changes in the behaviour of its electrons. This has led to the idea of developing "smart" materials which, in a controlled way, modify their electronic properties according to the stress applied. In principle, this would allow modulation of the way they absorb light, their electrical conductivity, thermal conductivity and other qualities. The word straintronics, which could be translated as "tensiotronics", has been coined to describe the study and application of this phenomenon.
In recent theoretical work, carried out together with Maurice Oliva-Leyva of UNAM's Institute for Materials Research, we have analysed the effect of sound waves on the electronic behaviour of graphene. Our results, published in the Journal of Physics: Condensed Matter, suggest the possibility of using mechanical deformations to collimate the electrons in the material, i.e. to generate a beam that propagates in a certain direction. The finding is a first step towards manipulating electrons in graphene using sound waves and opens the door to several applications.
"Relativistic" electrons and electromagnetic waves
The electrons in graphene behave very differently from their counterparts in three-dimensional materials. In a three-dimensional semiconductor, such as silicon, the energy of the electrons is proportional to the square of their velocity. In graphene, on the other hand, the energy is directly proportional to the velocity of these particles. From a mathematical point of view, this relationship is analogous to the one satisfied by relativistic particles, i.e., those that move at speeds very close to the speed of light.
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