Superballistic Electrons: Superconductivity Replacement?

One would imagine that when more than one people try to push themselves through a small area, passing through becomes more and more difficult as the number of people increases. Which is intuitively true. If you are alone it is easier to through a door, but if four people try to do that all at once, you would be pushing each other, and take longer to get through, and perhaps might also get stuck.

But that is apparently not the case with electrons, or similarly with gas molecules. A study by MIT physicists headed by Leonid Levitov, posted in Nature, shows that the more the merrier. The team found that when more than one electrons, a bunch of them, is made to go through a thin metal tube, it is easier for them to pass through, and that too with speeds that were previously unimaginable. Another team in Israel found the same results. 

MIT-Superball_2
Particle World gets more weird. It is easier to go through a small opening, if everyone goes at once, rather than one at a time!

Let me use gas molecules to explain the above discovery. Gases have been discovered to show the same behaviour. When you observe a gas molecule going from one end to the other inside a tube, one would wonder it travels in a straight path. But that is wrong. Because of thermal agitations, the molecules can hardly be said to travel in a straight line for long, they experience collisions with each other and the walls of the tube. The collisions with each other is elastic, i.e no energy is lost, but the collisions with the walls is inelastic which is accompanied by loss of energy, which reduces the speed. Since it is seen that the molecules collide more often with the walls than with each other when separately travelling through a hole, it means more energy is lost. In short, the molecules interact in such a way so as to increase speed. Similar is the case with electrons. More the merrier. A single electron when collides with the walls of the metal, looses energy and hence speed. But when travelling in a bunch, the individuals of the group interact or collide more with each other than the walls overall, and since these collisions are elastic, there is no loss in their speeds.

“[W]e can overcome this boundary that everyone thought was a fundamental limit on how high the conductance could be,”  Leonid Levitov, told David L. Chandler at MIT News.

Our present understanding of conduction in nano-electronics is that the speed of electrons is limited by the Landbauer’s ballistic limit, but the speeds achieved by the process crosses the limit, and this is why the electrons have been called superballistic electrons, and the process is called superballistic flow. This can have wide applications in electronics. Where superconductivity require very low temperatures ~5K, and are costly, the newly discovered phenomena, can take place at room temperature, and is actually favoured by rise in temperature! Zero resistance for every-day electronics might not be a far. It has also been observed that as the density increases, after a certain value, the hydrodynamic pressure required to push the bunch get lesser.

“Superballistic flow is favoured by temperature, rather than being hindered by it.”

Thus, viscous flow can increase electron speeds beyond the previously held limits.Right now, more research is being done in the topic. Stanford physicist David Goldhaber-Gordon said that the theoretical result can be tested in the material graphene, and with this new effect in one hand, superconductivity better watch its back, because we might have come across a better alternative. The team agrees the findings are completely theoretical, but various aspects of it have already been proven experimentally.

MIT-Phonon-Scattering_0
Superballistic flow can revolutionize current conduction in electronics, with near-zero resistance.

It is just a matter of time that we will be seeing the results of this finding. If indeed it can be employed in everyday electronics, it would revolutionize the field. Near-zero resistance would mean less power loss through heating, and better and efficient transmission of signals. Happy Reading!

-The Cosmogasmic Person

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