Plumbene Has Finally Been Synthesized Thanks To a Team in Japan

Researchers at Nagoya University have finally synthesized a once purely theoretical material called Plumbene.

Graphene has a new cousin thanks to a group of scientists at Nagoya University. For the first time in history, they have been able to successfully synthesize a formerly purely theoretical material called Plumbene. 

This development could have wide-ranging implications for topological insulators in the not too distant future.

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What is Plumbene?

Plumbene is a lead(Pb)-based 2-D honeycomb material that was, until now, purely theoretical. Ostensibly similar to Graphene in structure, Plumbene could provide a robust 2-D topological insulator of the future.

A topological insulator is, according to Wikipedia, any material with "non-trivial symmetry-protected topological order that behaves as an insulator in its interior but whose surface contains conducting states, meaning that electrons can only move along the surface of the material." 

Unlike others (Graphene for example), Plumbene should, according to researchers, be able to exhibit the Quantum Spin Hall Effect above room temperature. For this reason, finding a reliable and cheap method of synthesizing Plumbene has been considered to be an important goal of materials science research.

Art imitates life, so it is said

A research team at Nagoya University have been able to create Plubmene by annealing (heating and cooling slowly) an ultrathin lead (Pb) film on palladium Pd(111). By using this method they were able to create a surface material with the signature honeycomb structure of a 2D monolayer, as revealed by scanning tunneling microscopy (STM).

But, they were also surprised to find that underneath the Plumbene a palladium-lead (Pd-Pb) alloy thin film also formed. This film had a bubble structure reminiscent of a Weaire-Phelan structure which partitions space into cells of equal volume with the least total surface area of the walls between them.

This, say the researchers, helps solve the "Kelvin Problem".

This kind of structure tends to be used to represent an idealized foam of equally sized bubbles. The structure was first devised back in 1993 by Trinity College Dublin physicist Denis Weaire

Plumbene Weaire–Phelan structure
An example of a Weaire–Phelan structure composed of polyhedral cells. Source: Tomruen/Wikimedia Commons

This structure was also the inspiration behind the 2008 Beijing Olympics Beijing National Aquatics Center aka "Water Cube"

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Research leader, Professor Junji Yuhara, was quick to point out that this is not the first time architecture has been inspired by the work of material scientists.

"Architect Buckminster Fuller designed the geodesic sphere for the World Expo 1967 in Montreal, and later the Buckminster Fullerene, C60, was named after him." - he pointed out.

"Both plumbene and the 'nano water cube' are a beautiful addition to the Nano Nature World. The buildings of the 2020 Tokyo Olympics, the 2024 Paris Olympics, Expo 2020 Dubai, Expo 2023 Buenos Aires, Expo 2025 Osaka, and so on may also be placed in the spotlight again as future new materials," he added.

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plumbene beijing water cube
The Beijing "Water Cube". Source: Andrey Belenko/Flickr

Why is Plumbene important?

2-D materials that are made from Group 14 elements of the Periodic Table are widely considered by materials scientists as ideal candidates as topological insulators.

Plumbene, for example, has generated much attention because it has the largest spin-orbit interaction of all of them. This is because of Pb's orbital electron structure which should give Plumbene the largest energy band gap for all Group 14 elements.

The creation of this material could have wide-ranging implication for the development of future topological insulators

plumbene structure
Source: Advanced Materials

"The advent of Plumbene", remarks Professor Yuhara, "has been long awaited, and comes after the creation of Silicene in 2012, Germanene in 2014 and stanene in 2015. It will certainly launch a rush for applications." - Yuhara said.

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This study was originally published earlier this month in the journal Advanced Materials

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