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What Is Chirality?

Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.

Symmetries are appealing because of their visual as well as manipulative properties. Oftentimes they illuminate complex physics problems and reduce them into such beautiful solutions. Rotational is easy to demonstrate with objects, but what about reflectional? Taking the object and reconfiguring it to make a mirror image will oftentimes give you something new with unexpected properties. Welcome to the field of chirality.

Chiral Chemistry

How do scientists generate the chiral molecule they want? The trick lies in the type of polarized light they are dealing with, according to research from the University of Tokyo. It comes in two formats, either right-circularly polarized (spinning clockwise) or left-circularly polarized (spinning counter clockwise). The research team used this polarized light on gold nanocuboids that rested on a TiO2 substrate, generating different electric fields for each type. This in turn would cause the gold to orient itself differently before being bonded with Pb2+ ions via a “plamson-induced charge separation,” causing chiral molecules to develop (Tatsuma).

Orientated chirlaity.

Orientated chirlaity.

Chiral Magnetism

In the drive for better ways to save digital data, chiral patterns have been identified under the right magnetic conditions. When you consider the properties of magnetism, this isn’t surprising. It is composed of magnetic moments each particle has and the direction of their arrows forms a slope-field of sorts. This can definitely create chiral patterns, but sometimes one is better suited for us from an energetic standpoint. Right-handed configurations have been shown to offer us a lowest energy starting point and so are desired in helimagents, whose arrows are easily manipulated and also have chiral properties naturally. But they need to be at low temperatures and therefore are not as cost effective. Hence why the development by Denys Makarov and team are important, for they have developed chiral properties from iron-nickel magnets. These are of course quite easily accessible and rather interestingly develop their chirality when the magnet is a thin, micrometer thick parabolic shape! When the magnetic field was flipped to a certain value the chirality also flipped rather easily. Obviously using a critical magnetic field value to change the state of the material would be useful in data applications (Schmitt).

Chiral Anomaly

In the 1940s, Hermann Weyl (Institute for Advanced Study in Princeton) and team uncovered a fascinating property of extremely small massed objects: they exhibit chirality that causes them to split “into left and right handed populations that never intermix.” Only via the introduction of magnetic and electric fields can interchangings take place, with other by-products made as it happened. The anomaly played a big role in 1969 when Stephen Adler (Institute for Advanced Study in Princeton), John Bell (CERN) and Roman Jackie (MIT) found it was responsible for the extremely different decay rate (by a factor of 300 million) of neutral pions when compared to charged pions. This requires accelerators which makes study of the anomaly difficult, so when a theoretical set up involving crystals and intense magnetic fields was developed in 1983 by Holger Bech Nielsen (University of Copenhagen) and Masao Ninomiya (Okayama Institute for Quantum Physics), many were interested.

It was finally achieved with a special material known as a Dirac semi-metal, which has topological features that enable electrons to be placed in the material in locations that under quantum conditions act like massless left handed vs right-handed particles. With the semi-metal being made of NA3Bi, it was studied by Jun Xiong (Princeton) under super chilled conditions, allowing quantum properties to exist as well as magnetic field manipulation. When said field was parallel to the electric field coursing through the crystal, the chiral particles began to intermix, resulting in an “axial current plume" where current fights loss caused by impurities in the material. This would be the extra phenomena that the chiral anomaly said could happen (Zandonella).

A Brief Note

It is worth mentioning that much literature exists on the chirality of biological molecules, like DNA and amino acids. I am not a biologist and so I leave it to others better suited on the topic to discuss that. Here was but a chemistry and physics-based presentation. Please, do read up more on the topic. It certainly has its twists.

Works Cited

Schmitt, Simon. “An astonishing parabola trick.” Innovations-report.com. innovations report, 03 Sept. 2019. Web. 09 Oct. 2019.

Tatsuma, Tetsu. “Polarized light: A simple route to highly chiral materials.” Innovations-report.com. innovations report, 09 May 2018. Web. 03 Oct. 2019.

Zandonella, Catherine. “Long-sought chiral anomaly detected in crystalline material.” Innovations-report.com. innovations report, 09 Apr. 2015. Web. 30 Sept. 2019.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2020 Leonard Kelley