A new route to dissipationless electronics

Aug 19, 2012
This is a depiction of the quantum Hall effect (left) and the quantum anomalous Hall effect (right). Credit: RIKEN

A team of researchers at RIKEN and the University of Tokyo has demonstrated a new material that promises to eliminate loss in electrical power transmission. The surprise is that their methodology for solving this classic energy problem is based upon the first realization of a highly exotic type of magnetic semiconductor first theorized less than a decade ago - a magnetic topological insulator.

Development of energy saving technologies is one of the central pursuits of modern science. From advancing alternative energy resources like wind and to improving the infrastructure of the electrical power grid, this pursuit by scientists and engineers takes on a variety of forms. One focus in recent years has been eliminating in the transmission of power itself, which by some estimates consumes more than 10% of all energy being produced. The research team has demonstrated a new material - a topological insulator - that can eliminate this loss.

At left, the active area of magnetic topological insulator (dark gray) is 3 microns across and only 70 atoms thick. The blue background is an insulating gate dielectric and the yellow regions are metallic electrodes. At right, the internal magnet favors the "off" state of the transistor on the left. This is evidence for a new type of magnetic semiconductor. Credit: RIKEN

The work by the RIKEN/UT collaboration is closely related at a landmark discovery from the 1980s, the so-called quantum Hall effect. That effect is known to produce dissipationless electricity channels, but it requires large, cumbersome magnets to produce fields 100,000 larger than the earth's magnetic field for its operation. The RIKEN/UT collaboration circumvented this difficulty by using an exotic type of semiconductor predicted to exhibit a similar effect. In contrast to the , this effect, known as the quantum anomalous Hall effect, stems from the semiconductor's own magnetization rather than from an external one. At the heart of this new phenomenon is the interaction between and the topological 's current carrying particles (known as Dirac fermions), the latter of which are unique because they behave as if they have zero mass.

This is a depiction of realization of edge modes on sample surface. At left, a schematic representation of magnetic structure is shown, dark and light representing down and up polarization, respectively. At right, the corresponding edge mode structure is shown, with the green arrows representing chiral modes at magnetic reversal. The electrical current flows in the same manner as in the quantum Hall and anomalous quantum Hall states. Credit: RIKEN

The devices produced by the RIKEN/UT team are a robust "proof of principle", demonstrating that this new type of dissipationless transport can be harnessed in prototype transistors. While currently requiring cryogenic conditions, improvements in materials design promises to improve the stability of the magnets, making it possible to operate them at higher temperatures. By doing away with external stimuli such as magnetic fields and, in the future, cryogenic cooling, these new magnetic topological insulators may represent the most efficient path to modernizing the power grid by eliminating loss in energy transfer.

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More information: Dirac-fermion-mediated ferromagnetism in a topological insulator, Nature Physics, 2012, DOI: 10.1038/nphys2388

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Sonhouse
not rated yet Aug 19, 2012
This effect is distinct from what we think of as superconductors? Like repelling magnetic fields from entering?

They also have to make their compound in large quantities, they also have to beat the temperature record of the highest temperature superconductors.
MrVibrating
1 / 5 (2) Aug 19, 2012
So can i get my 50THz CPU now please..?
Eikka
not rated yet Aug 20, 2012
One focus in recent years has been eliminating energy loss in the transmission of power itself, which by some estimates consumes more than 10% of all energy being produced.


The vast majority of lost energy in the transmission grid comes from conversion losses and capacitive and radiative leakage - not from the actual resistive losses in the wires.

Any time a current goes through a wire, it makes an electric and a magnetic field that couples to everything around it. That's why you can stand under a high tension line with a fluorescent tube and have it light up.

Impendance is the square root of the sum of the squares of reactance and resistance. Lossless conductors simply remove the resistance out of the equation.
Sonhouse
not rated yet Aug 20, 2012
One focus in recent years has been eliminating energy loss in the transmission of power itself, which by some estimates consumes more than 10% of all energy being produced.


The vast majority of lost energy in the transmission grid comes from conversion losses and capacitive and radiative leakage - not from the actual resistive losses in the wires.

Any time a current goes through a wire, it makes an electric and a magnetic field that couples to everything around it. That's why you can stand under a high tension line with a fluorescent tube and have it light up.

Impendance is the square root of the sum of the squares of reactance and resistance. Lossless conductors simply remove the resistance out of the equation.

That is true for ordinary AC lines measuring in hundreds of thousands of volts or even megavolts but the latest lines are DC, with stacked transistors in series to handle the huge voltages. DC has no radiation,capacitive or magnetic losses.
Sonhouse
not rated yet Aug 20, 2012
I think any losses from high voltage DC lines would be corona discharges and dirty insulators which can be severe if you don't keep your insulators clean.
Tektrix
not rated yet Aug 20, 2012
@Sonhouse HVDC has a lot of advantages over AC for long-haul. The Wikipedia article has some good info:
http://en.wikiped...smission
ValeriaT
not rated yet Aug 20, 2012
This effect is distinct from what we think of as superconductors?
Actually a deep similarities exist here. Before ten years J.F.Prins observed the superconductivity at room temperature at the surface of diamond containing implanted oxygen ions. These ions attracted the free electrons to the surface of diamond and these electrons formed a dense superfluid here.
The topological insulators work in similar way. They're composed of large atoms with small spaces between it, so that the electrons are expelled from atom lattice into its surface like the droplets of mercury from thick sponge. These electrons are mutually compressed there in similar way, like the electrons at the surface of Prins's superconductor, their repulsive forces overlap and compensate mutually, so that these electrons are moving freely here. The only difference is, whereas topological insulators are studied extensively, the J.F.Prins's finding was ignored with mainstream science.
unknownorgin
not rated yet Aug 23, 2012
It is well known that an electron acelerated through an electrostatic potential gains kinetic energy and upon hitting a conductive surface or atom disapates this energy in the form of electromagnetic radiation so using a magnetic field to dampen the oscillation of the electron shell would prevent this energy convertion. What a powerfull electromagnet this could make for energy storage. (excuse my spelling)
Eikka
not rated yet Aug 30, 2012
That is true for ordinary AC lines measuring in hundreds of thousands of volts or even megavolts but the latest lines are DC, with stacked transistors in series to handle the huge voltages. DC has no radiation,capacitive or magnetic losses.


Yes, but the DC system has significant conversion losses because the transistors and other semiconductor devices used to control it suffer a forward voltage loss over the junctions, so they waste significant amounts of power getting the DC in and out of the powerlines.

That's why HVDC lines are only reasonable at very long distances where ordinary AC lines would have more loss. Over short distances and medium to low voltages, they simply waste more power.