In the relatively new scientific frontier of topological insulators, theoretical and experimental physicists have been studying the surfaces of these unique materials for insights into the behavior of electrons that display some very un-electron-like properties.
In topological insulators, electrons can behave more like photons, or particles of light. The hitch is that unlike photons, electrons have a mass that normally plays a defining role in their behavior. In the world of quantum physics, where everyday materials take on surprising and sometimes astonishing properties, electrons on the outer surface of these insulators behave and look uncharacteristically like light.
These unique properties have piqued the interests of scientists who see future applications in areas such as quantum computing and spintronics, or other realms rooted in the manipulation of electronic properties. The early challenge to those researchers is to begin to understand some simple ground rules for controlling these materials.
Boston College researchers report that the placement of tiny ripples on the surface of a topological insulator engineered from bismuth telluride effectively modulates so-called Dirac electrons so they flow in a pathway that perfectly mirrors the topography of the crystal's surface.
Associate Professor of Physics Vidya Madhavan and Assistant Professor of Physics Stephen Wilson report in the current online edition of Nature Communications that scanning tunneling microscopy is capable of revealing the characteristics of these tiny waves as they rise and fall, enabling the researchers to draw a direct connection between the features of the ripples and modulation of the waves across the material's surface.
Instead of chaotic behavior, the electrons flow in a path that mirrors the metal composite's surface, the team reports in an articled titled "Ripple-modulated electronic structure of a 3D topological insulator."
"What we've discovered is that electrons respond beautifully to this buckling of the material's surface," said Madhavan, the project director.
So harmoniously do the waves flow across the ripples – placed approximately 100 nanometers apart – that the researchers say further modifications of the crystal's "nanoscale landscape" could produce enough control to produce a one-dimensional quantum wire capable of carrying current with no dissipation.
The rippled surface appears to exert greater control and run less risk of creating imperfections than other methods, such as introducing chemical dopants, used in attempts to modulate the flow of electrons on the surface of other topological insulators, the researchers found.
Madhavan said the team had to provoke the electrons, which lay placidly atop the surface-state of the insulator, much like the glassy surface of an undisturbed lake. The team disrupted the electrons by introducing impurities, which had an effect similar to that of dropping a stone in a calm lake. This provocation produced waves of electrons that behave like waves of light as they travel pathways that mirror the contours created in the crystal.
"We did not expect the electrons to follow the topography," said Madhavan. "The topography imposes a sinusoidal potential upon the waves. The ripples create that potential by giving the electrons a landscape to follow. This is a way of possibly manipulating these electrons in topological insulators."
In addition to Madhavan and Wilson, the project team included post-doctoral researcher Yoshinori Okada and graduate students Wenwen Zhou, Daniel Walkup and Chetan Dhital.
NOTE: The report "Ripple-modulated electronic structure of a 3D topological insulator" can be cited via a digital object identifier (DOI) number. The DOI for this article is 10.1038/ncomms2150
Ed Hayward | EurekAlert!
Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)
Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences