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Opposites attract. It'southward one of the key rules that explain why electricity and magnetism practise what they do. Magnets and charge accept two "flavors" we call poles, like charges repel, and the electrical polarity of the arrangement determines which style current will catamenia. Except — apparently graphene puts an asterisk after Maxwell's equations.

Two teams of physicists merely found show that graphene makes electrons act less like accuse carriers moving at relativistic speeds and more than similar a viscid liquid, flowing against the electrical current in eddies and whirlpools like those at a river's edge. That property makes electrons flow against electrical polarity in a phenomenon that physicists are calling "negative resistance," and as Nature Physics and Science report, we've finally seen it happen at room temperature.

Negative resistance

Graphene has a strange cross-department of electromagnetic properties, including loftier conductance and low resistance, like metals. Unlike a metal, though, graphene does some truly bizarre things to the electrons going through information technology. When y'all run electric current through a wire, it mostly moves in smooth, laminar flow, in a way we usually call "ballistic." Imperfections in the material are the dominant deflecting force introducing turbulence into the arrangement, and that's a minor effect.

We thought graphene acted the aforementioned way, with the only electron deflections occurring at junctions in the sheet. When yous apply a voltage to a graphene ribbon, though, but some of the current moves in predictable, laminar Ohmic catamenia. Professor Leonid Lebitov of MIT and Professor Gregory Falkovich of Israel's Weizmann Institute of Science demonstrated that some of information technology displays negative resistance: Instead of slowing electrons and dissipating their energy through heat as with an Ohmic resistor, the electrons are deflected and spring up in niggling eddies that motility confronting the electrical polarity of the system, like a viscous liquid.

Andre Geim, a professor of condensed matter physics at the University of Manchester, ran with that thought and measured the viscosity observed in the eddies. He and his team "detected the vortices predicted by Levitov's group and showed that the electron liquid in graphene was 100 times more than viscous than dear, contrary to the universal belief that electrons comport like a gas."

Fig 1 - Current streamlines and potential map for viscous and ohmic flows - from Nature Physics

Graphene's electrodynamic properties lead to viscous current flows, creating tiny whirlpools that cause electrons to travel confronting electrical polarity. White lines show current streamlines, colors show electrical potential, and green arrows evidence the direction of current, for viscous (acme console) and normal (ohmic, bottom panel) flows. Paradigm: Nature Physics

This enquiry is then new that we're non even sure how to apply the findings nonetheless. I of the potential implications is that heat transfer is strongly coupled to charge transfer, so there will probably exist related thermal conductance phenomena to exist uncovered hither. As noted in Nature, "Viscous [electron] flow results in a highly circuitous heating blueprint with intense hot spots nearly contacts and common cold arc-shaped patches at vortices surrounded past warmer regions."

Fig 3 - heating patterns for viscous and ohmic flows - Nature Physics

White arrows show electric current direction. Viscid menstruation shows a highly circuitous heating design.  Ohmic catamenia (bottom) shows an substantially featureless rut production charge per unit decaying monotonously away from contacts.  Image: Nature Physics

These experiments mark the first time we've ever been able to straight observe these long-predicted effects of graphene chemical science. What's more, they offer a window into the macroscale implications of breakthrough physics. While quantum effects are usually insignificant at scales larger than individual particles, in the graphene surroundings they play a dominant office, says Professor Levitov via MIT news. In this setting, "we show that [the way charge carriers move] has commonage behavior similar to other strongly interacting fluids, like h2o." Given how hard graphene still is to produce in quantity, though, it may be that we won't know how to use information technology until we can brand enough to use.

Now read What is graphene?

The original articles (both paywalled) are at http://dx.doi.org/doi:x.1126/science.aad0201 and http://dx.doi.org/doi:10.1038/nphys3667.