Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists paint quantum electronics with beams of light

12.10.2015

Chance effect of lab's fluorescent lights leads to discovery

A team of scientists from the University of Chicago and the Pennsylvania State University have accidentally discovered a new way of using light to draw and erase quantum-mechanical circuits in a unique class of materials called topological insulators.


This is a picture of an artist's rendition of optically-defined quantum circuits in a topological insulator.

Credit: Peter Allen

In contrast to using advanced nanofabrication facilities based on chemical processing of materials, this flexible technique allows for rewritable 'optical fabrication' of devices. This finding is likely to spawn new developments in emerging technologies such as low-power electronics based on the spin of electrons or ultrafast quantum computers.

The research is published today in the American Association for the Advancement of Science's new online journal Science Advances, where it is featured on the journal's front page.

"This observation came as a complete surprise," said David D. Awschalom, Liew Family Professor and deputy director in the Institute of Molecular Engineering at UChicago, and one of two lead researchers on the project. "It's one of those rare moments in experimental science where a seemingly random event -- turning on the room lights -- generated unexpected effects with potentially important impacts in science and technology."

The electrons in topological insulators have unique quantum properties that many scientists believe will be useful for developing spin-based electronics and quantum computers. However, making even the simplest experimental circuits with these materials has proved difficult because traditional semiconductor engineering techniques tend to destroy their fragile quantum properties. Even a brief exposure to air can reduce their quality.

In Science Advances, the researchers report the discovery of an optical effect that allows them to "tune" the energy of electrons in these materials using light, and without ever having to touch the material itself. They have used it to draw and erase p-n junctions -- one of the central components of a transistor -- in a topological insulator for the first time.

Like many advances in science, the path to this discovery had an unexpected twist.

"To be honest, we were trying to study something completely different," said Andrew Yeats, a graduate student in Awschalom's laboratory and the paper's lead author. "There was a slow drift in our measurements that we traced to a particular type of fluorescent lights in our lab. At first we were glad to be rid of it, and then it struck us -- our room lights were doing something that people work very hard to do in these materials."

The researchers went back to Bulley & Andrews, the contractor that renovated the lab space for more information about the lights. "I've never had a client so obsessed with the overhead lighting," said Frank Floss, superintendent for Bulley & Andrews Construction. "I could have never imagined how important it would turn out to be."

The researchers found that the surface of strontium titanate, the substrate material on which they had grown their samples, becomes electrically polarized when exposed to ultraviolet light, and their room lights happened to emit at just the right wavelength. The electric field from the polarized strontium titanate was leaking into the topological insulator layer, changing its electronic properties.

Awschalom and his colleagues found that by intentionally focusing beams of light on their samples, they could draw electronic structures that persisted long after the light was removed.

"It's like having a sort of quantum etch-a-sketch in our lab," he said. They also found that bright red light counteracted the effect of the ultraviolet light, allowing them to both write and erase. "Instead of spending weeks in the cleanroom and potentially contaminating our materials," said Awschalom, "now we can sketch and measure devices for our experiments in real time. When we're done, we just erase it and make something else. We can do this in less than a second."

To test whether the new technique might interfere with the unique properties of topological insulators, the team measured their samples in high magnetic fields. They found promising signatures of an effect called weak anti-localization, which arises from quantum interference between the different simultaneous paths electrons can take through a material when they behave as waves.

"One exciting aspect of this work is that it's noninvasive" said Nitin Samarth, Professor and Downsbrough Head of Physics at Penn State, and a lead researcher on the project. "Since the electrical polarization occurs in an adjacent material, and the effect persists in the dark, the topological insulator remains relatively undisturbed. With these fragile quantum materials, sometimes you have to use a light touch."

To better understand the physics behind the effect, the researchers conducted a number of control measurements which showed that the optical effect is not unique to topological insulators, but that it can act on other materials grown on strontium titanate as well.

"In a way, the most exciting aspect of this work is that it should be applicable to a wide range of nanoscale materials such as complex oxides, graphene, and transition metal dichalcogenides," said Awschalom.

"It's not just that it's faster and easier. This effect could allow electrical tuning of materials in a wide range of optical, magnetic and spectroscopic experiments where electrical contacts are extremely difficult or simply impossible."

Media Contact

Steve Koppes
skoppes@uchicago.edu
773-702-8366

 @UChicago

http://www-news.uchicago.edu 

Steve Koppes | EurekAlert!

More articles from Physics and Astronomy:

nachricht SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>