How to Control Heat Flow with a Magnet?

In a quirky quantum-mechanical connection, a mag breadic force orbit rat control the break away of conflagrate cross slipway a interlace of cable. The kindle is carried by quantum swans of electrons, and waves traveling or so the hand-build carrefour to bolster or limit the lean dep closinging on the strengths of the magnetic palm threading the loop, a pair of physicists predicts in the 15 April PRL. antecedent experiments confirm the prediction. Curiously, still as electrons skirt fondness across the little device, no electric accredited hunts through it. For decades, physicists substantiate cognise that a magnetic field disregard meet the flow of electricity through a cable that splits and rejoins to condition a visit resembling a duty circle in the middle of a road. Known as the Aharonov-Bohm effect, the phenomenon arises because each electron is described by a quantum wave that splits, so that half(prenominal) of it flows around one font of the ring and half flows around the other side. When the dickens waves recombine on the further side of the ring they squeeze out overlap peak-to-peak to maximize the true, or peak-to-valley to smirch it. How the waves line up depends on the strength of the magnetic field threading the loop. The field switchs the peaks in the waves going around the two halves of the ring by different amounts. Bizarrely, the field can shift the waves even if it is confined to the hole in the ring and does not go by into the metal through which the electrons flow. Thanks to quantum mechanics, the electrons tonus the effect of a field that they never travel through. save in some ways electrons also behave bid particles, so they can consider energy and, hence, heat, as they go from the hotter end to the colder end of a wire. And a magnetic field can affect the heat flow through a wire with a loop in much the equal way the field can affect the flow of electricity, wager Zhigang Jiang and Venkat Chandrasekar of Northwestern Universi! ty in Evanston, Illinois. The researchers study a gizmo known as an Andreev interferometer--essentially a wire a few microns pine with a loop of superconducting wire attached to it like a side street that branches from a highway and circles around to flow back into it at the same point. The electrons in the super landing field director have wave-like characteristics that are easier to detect than those in median(a) metal. match to the calculations, the waves of electrons zipping all the way around the superconducting detour cancel or reinforce themselves at the point where they meet the main wire. much(prenominal) hinderance limits the number of quantum states through which electrons in the ordinary conductor can cross the intersection.

That limits the flow of heat, much as a unsympathetic lane limits traffic flow on a highway. So as the magnetic field increases, the flow of heat from the hotter to the colder end of the wire climbs and falls repeatedly, just as the electrical original rises and falls in the Aharonov-Bohm effect. However, in this case, no electrical current flows, Chandrasekhar says. Basically, electrons go from one end to the other, give up their energy, and so go back, he says, so theres no net flow of electric charge. In preliminary experiments, the researchers have seen the predicted heat flow oscillations [1]. At first glance, the superconducting ring and magnetic field tonus to the fore to be irrelevant, so the result is surprising, says Dan Prober of Yale University in naked Haven, Connecticut. Prober notes that to pick out the subtle effect, Chandrasekha r had to bring to addher several experimental techni! ques: He does elegant, hard, and sometimes crazy hard experiments. --Adrian Cho Adrian Cho is a do work writer in Grosse Pointe Woods, Michigan References: [1] Z. Jiang and V. Chandrasekhar, Quantitative measurements of the thermal resistance of Andreev interferometers, If you want to get a full essay, order it on our website: OrderCustomPaper.com

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