Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Molecular blockade

21.06.2010
Artificial ‘molecules’ with an asymmetric structure can control the flow of electrons in semiconductor materials

Nanoscale devices confine electrons and enable manipulation of electron spin—an inherent property akin to the direction in which the particle is rotating. An unexpected mechanism for this control in asymmetric structures has now been reported by Keiji Ono at the RIKEN Advanced Science Institute, Wako, in collaboration with a team of researchers from Japan and Taiwan.

Artificial systems that trap electrons in a tiny volume can display many of the properties of atoms because they create an analogous series of discrete electron energy levels. “One example is the Zeeman Effect in which an applied magnetic field splits a single electron energy level into two, depending on its spin,” explains Ono.

Taking this analogy further, two closely spaced ‘artificial atoms’ can behave like an artificial molecule. In principle, it is possible to transfer an electron between these atoms by tuning the energy level of an electron in one atom to that of the second by, for example, applying an electric field. Indeed, this phenomenon, known as resonant tunneling, occurs in artificial molecules consisting of two identical atoms. Ono and his team showed, however, that the situation is not so simple in artificial molecules comprising two different atoms.

They investigated a structure that was a stack of alternating layers of semiconductor. Electrons become trapped in the semiconductor with the smaller bandgap by the surrounding layers of wide-bandgap material. The top ‘atom’ was 7.5 nanometers thick and made of indium gallium arsenide. A 6.5-nanometer barrier separated this from the second atom: 10 nanometers of gallium arsenide. Etched pillars with a diameter of less than one micrometer confined the electrons in the transverse direction.

The difference in size and composition meant that the Zeeman Effect was stronger in the top atom than the bottom one. This made it impossible to align both of the Zeeman-split levels in the two atoms at the same time. Ono and colleagues demonstrated that because of this, when an energy state from one atom is aligned with one in the second, the electron flow through the molecule reduces, an effect they call spin blockade. The flow increased when they tuned the two Zeeman levels in one atom to the midpoint of those in the other atom.

“This finding can be used as a basic tool for selecting, filtering, or initializing an individual electron spin,” comments Ono. “I hope this can be applied to quantum information technology.”

The corresponding author for this highlight is based at the Low Temperature Physics Laboratory Single Quantum Dynamics Research Group, RIKEN Advanced Science Institute

Journal information

1. Huang, S.M., Tokura, Y., Akimoto, H., Kono, K., Lin, J.J., Tarucha, S. & Ono, K. Spin bottleneck in resonant tunneling through double quantum dots with different Zeeman splitting. Physical Review Letters 104, 136801 (2010)

gro-pr | Research asia research news
Further information:
http://www.riken.jp
http://www.researchsea.com

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 >>>