Two-dimensional organic lattices are easier and safer to work with than inorganic materials for spintronic and quantum computing applications.
Using sophisticated theoretical tools, Agency for Science, Technology and Research (A*STAR) researchers, in Singapore, have identified a way to construct topological insulators — a new class of spin-active materials — out of planar organic-based complexes rather than toxic inorganic crystals .
A*STAR researchers have used a combination of quantum calculations and band-structure simulations to design topological insulators based on two-dimensional organic-based nanosheets.
The unique crystal structure of topological insulators makes them insulating everywhere, except around their edges. Because the conductivity of these materials is localized into quantized surface states, the current passing through topological insulators acquires special characteristics. For example, it can polarize electron spins into a single orientation — a phenomenon that researchers are exploiting to produce ‘spin–orbit couplings’ that generate magnetic fields for spintronics without the need for external magnets.
Many topological insulators are made by repeatedly exfoliating inorganic minerals, such as bismuth tellurides or bismuth selenides, with sticky tape until flat, two-dimensional (2D) sheets appear. “This gives superior properties compared to bulk crystals, but mechanical exfoliation has poor reproducibility,” explains Shuo-Wang Yang from the A*STAR Institute of High Performance Computing. “We proposed to investigate topological insulators based on organic coordination complexes, because these structures are more suitable for traditional wet chemical synthesis than inorganic materials.”
Coordination complexes are compounds in which organic molecules known as ligands bind symmetrically around a central metal atom. Yang and his team identified novel ‘shape-persistent’ organic ligand complexes as good candidates for their method. These compounds feature ligands made from small, rigid aromatic rings. By using transition metals to link these organic building blocks into larger rings known as ‘macrocycles’, researchers can construct extended 2D lattices that feature high charge carrier mobility.
Pinpointing 2D organic lattices with desirable topological insulator properties is difficult when relying only on experiments. To refine this search, Yang and colleagues used a combination of quantum calculations and band structure simulations to screen the electronic activity of various shape-persistent organic complexes. The team looked for two key factors in their simulations: ligands that can delocalize electrons in a 2D plane similar to graphene and strong spin–orbit coupling between central transition metal nodes and ligands.
The researchers’ new family of potential organic topological insulators has a 2D honeycomb macrocycles containing tri-phenyl rings, palladium or platinum metals, and amino linking groups. With promising quantum features and high theoretical stability, these complexes may serve as topological insulators in real world applications.
“These materials are easy to fabricate, and cheaper than their inorganic counterparts,” says Yang. “They are also suitable for assembling directly onto semiconductor surfaces, which makes nanoelectronic applications more feasible.”
The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing and the Institute of Materials Research and Engineering. For more information about the team’s research, please visit the Materials Science & Engineering webpage.
 Zhou, Q., Wang, J., Chwee, T. S., Wu, G., Wang, X. et al.Topological insulators based on 2D shape-persistent organic ligand complexes. Nanoscale 7, 727–735 (2015).
Original article from A*STAR Research
A*STAR Research | Research SEA
Scientists from Hannover develop a novel lightweight production process
27.09.2017 | IPH - Institut für Integrierte Produktion Hannover gGmbH
PRESTO – Highly Dynamic Powerhouses
15.05.2017 | JULABO GmbH
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
12.12.2017 | Physics and Astronomy
12.12.2017 | Earth Sciences
12.12.2017 | Power and Electrical Engineering