Research finds a new way to control topological insulators
Research into a recently discovered class of materials shows they have the necessary characteristics to develop ultra-energy efficient electronics. Topological insulators (TI) are three-dimensional materials that conduct electricity on their surfaces, while the interior insulates.
The study found that the atoms are either stretched apart or pushed together at the grain boundaries and that strain can be used to 'tune' the material's unique electronic properties. Here, the boundaries appear dotted or puckered, while the Bi2Se3 grain forms in a triangular shape.
Their surfaces are particularly unique because the motion of the electrons is "protected" by symmetry, meaning electrons will keep moving without scattering even when they encounter defects and contamination.
In fact, electrons on the surface of TIs move so robustly scientists are trying to determine the best way to control or "tune" them in order to use them in next-generation electronics. Until now the only way to change the electronic state was to apply a magnetic or an electric field.
But research led by physicists at the University of Wisconsin-Milwaukee (UWM) has revealed a new method. The team proved that surface conduction on a bismuth selenide TI (Bi2Se3) can be enhanced or destroyed, depending on the kind of stress applied to the material at certain locations, called grain boundaries.
The work was published online March 16 in the journal Nature Physics.
Bi2Se3 is comprised of quintuple atomic layers of bismuth and selenium stacked on top of one another with strong lateral bonds and weak vertical ones between the layers. During its synthesis, when tiny crystalline Bi2Se3 grains coalesce, they form lines of intersection.
These grain boundaries, in which the atoms are either stretched apart or pushed together, can be compared to laying a tile floor starting with randomly placed ceramic pieces, says UWM Physics Professor Lian Li, principal investigator for the National Science Foundation grant supporting the research.
"They do not quite fit together perfectly," says Li, "which produces strain at the joints in the same way as tiles that don't align."
In proximity to a grain boundary where strain exists, the electronic properties on the Bi2Se3 surface are modified. In-plane pulling protects the flow of electrons because the bonds are strong, says Li. Conversely, in-plane compression increases the separation of the quintuple layers, destroying the surface states.
Unraveling the behaviors of TIs is important because it's a promising material for spintronics, an emerging field of nanoscale electronics that involves the manipulation of the electron spin as well as the charge.
By using the orientation of the electron spin, data transfer can be quicker and computing storage capacity increased.
"TIs would work well in spintronics," says Li, "because the spin and velocity of their surface electrons is locked in at right angles."
But first, scientist must find ways to manipulate their behaviors – even to create a simple "on-off" switch.
"So, when we apply compression at the boundaries, then you have no spin movement. All of the sudden, it becomes a switch," says Michael Weinert, UWM Distinguished Professor of Physics and director of the Laboratory for Surface Science. "The advantage here is control. You don't have to apply an electrical field, you can apply stress."
In addition to Li and Weinert, contributors to the paper include Ying Liu, Yaoyi Li and Shavani Rajput at UWM; Vlado Lazarov, Daniel Gilks, and Leonardo Lari at the University of York, U.K.; and Pedro Luis Galindo at Universidad de Cádiz, Spain.
Lian Li | EurekAlert!
A blueprint for clearing the skies of space debris
17.04.2015 | RIKEN
Quantum Physics – Hot and Cold at the Same Time
17.04.2015 | Ruprecht-Karls-Universität Heidelberg
Astronomers from Chalmers University of Technology have used the giant telescope Alma to reveal an extremely powerful magnetic field very close to a supermassive black hole in a distant galaxy
Astronomers from Chalmers University of Technology have used the giant telescope Alma to reveal an extremely powerful magnetic field very close to a...
A team of physicists from MPQ, Caltech, and ICFO proposes the combination of nano-photonics with ultracold atoms for simulating quantum many-body systems and creating new states of matter.
Ultracold atoms in the so-called optical lattices, that are generated by crosswise superposition of laser beams, have been proven to be one of the most...
According to new research out of the Texas A&M Health Science Center College of Medicine, that is indeed the case. Chetan Jinadatha, M.D., M.P.H., assistant...
Researchers from ICFO, MIT and UC Riverside have been able to develop a graphene-based photodetector capable of converting absorbed light into an electrical voltage at ultrafast timescales
The efficient conversion of light into electricity plays a crucial role in many technologies, ranging from cameras to solar cells.
Electrical charges not only move through wires, they also travel along lengths of DNA, the molecule of life. The property is known as charge transport.
In a new study appearing in the journal Nature Chemistry, authors, Limin Xiang, Julio Palma, Christopher Bruot and others at Arizona State University's...
13.04.2015 | Event News
25.03.2015 | Event News
19.03.2015 | Event News
17.04.2015 | Power and Electrical Engineering
17.04.2015 | Earth Sciences
17.04.2015 | Physics and Astronomy