Monday, 19 March 2018

Researchers Demonstrate Existence of New Form of Electronic Matter

Electronic Matter
According to the news that has been published in the journal ‘Nature’, engineers based at the University of Illinois have shown that a new form of electronic matter exists. It is called quadrupole topological insulators (QTI).

The properties exhibited by this electronic matter, QTI could bring about a wide range of possibilities in the computer field. It holds great promise in the manufacturing of low-power, robust computers and various devices, that are all defined at the atomic scale.

The topological insulators (TI) are basically electrical insulators on the inside but are conductors along the boundaries. This unique property exhibited by the topological insulators makes them a special type of electronic matter.

A group of electrons form their own phases within the materials. This can be either in the solid, liquid and gas phase, as is seen in water. They can also form an uncommon phase like a topological insulator.

What is this new phase of Electronic Matter? 

The new form of electronic matter is the Quadrupole Topological Insulator. According to theoretical physics, some of the topological insulators have an electrical property known as quadrupole moment.

As we see in a material, the electrons carry a charge. In the process, the material becomes bipolar, that is it contains the positive as well as the negative charge.

Now, in a higher order class of material, we get a quadrupole which is a coupling of two positive and two negative charges. In crystals, the electrons can arrange themselves in such a way that they can give rise to high-order multipoles besides the usual dipole units. In the case of multipoles, four or eight charges are collectively arranged in a unit. The basic forms of multipoles are the quadrupoles wherein two positive and two negative charges are coupled together in a unit.

An analog of a QTI was shown by the researchers of the University of Illinois. They demonstrated it by using a special material from printed circuit boards.

Each circuit has a square of four identical resonators or devices that can absorb electromagnetic radiation at a particular frequency. The boards were positioned in a grid to form the crystal analog.
Each of these resonators behaves like an atom and the connections between the resonators act as bonds between these atoms.

The system is then subjected to microwave radiation to measure the amount that has been absorbed by each of the resonators. This in turn will indicate the behavior of the electrons in an analogous crystal. If the microwave radiation absorbed by a resonator is more, then there are higher chances of finding an electron on the corresponding atom.

In the above experiment it was inferred that the corners of the connected resonators absorbed the microwave radiation at a specific frequency whereas the rest of the units did not do so. The researchers then separated the bottom row from the grid and on subjecting it to the microwave radiation, it was noticed that the next highest rows showed the topological effects on absorbing the radiation.

They concluded that the edges of a QTI are not conductive unlike that seen in a TI. It was only the corners which are active and they correspond to the four localized point charges that form the quadrupole moment.

On measuring the amount of microwave radiation each of the resonators absorbed in the QTI, it was confirmed that the resonant states was in a particular frequency range and localized in the four corners. This shows the existence of predicted protected states that would be filled up by electrons that would in turn form four corner charges.

With the experiment conducted, scientists are beginning to understand the possibilities of the new electronic matter and its application. As of now, the physicists can predict that the new form of electronic matter exists, but no material has been found to have these properties.

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