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 Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz

nachricht New functional principle to generate the „third harmonic“
16.02.2017 | Laser Zentrum Hannover e.V.

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Switched-on DNA

20.02.2017 | Materials Sciences

Second cause of hidden hearing loss identified

20.02.2017 | Health and Medicine

Prospect for more effective treatment of nerve pain

20.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>