Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Packing Electrons in a Nano Box: Control of Many-Body Correlation by Quantum Confinement

27.12.2010
Researchers have succeeded in controlling the few-particle quantum state of a semiconductor quantum dot, and changing its correlation energies.

A team headed by Dr. Takashi Kuroda, Senior Researcher, and Dr. Marco Abbarchi, Researcher, of the Quantum Dot Research Center (Managing Director: Kazuaki Sakoda), National Institute for Materials Science (President: Sukekatsu Ushioda), in joint research with Hokkaido University, succeeded in controlling the few-particle quantum state of a semiconductor quantum dot, and changing its correlation energies. This research achievement will make it possible to develop semiconductor non-linear devices which enable stable drive with low power consumption.


Atomic force microscope image of GaAs quantum dots used in this research.

When an electron and proton are brought into proximity in vacuum, the two particles are mutually attracted by Coulomb force and form a hydrogen atom. If another electron or proton is placed in addition, the many-body effect will result in formation of an ionic hydrogen molecule comprising a total of three particles.

This kind of quantum state also exists in solids. A pair of an electron and hole in a semiconductor form an exciton, analogous to a hydrogen atom. If another electron or hole is added, a complex state of three particles, called a charged exciton, is formed. In a semiconductor, unlike hydrogen in vacuum, it is possible to confine electrons an holes in quantum dots, i.e., an extremely small space on the order of several nanometers, and an increase in the stabilization energy of the multi-electronic state can be expected.

In this research, gallium arsenide (GaAs) quantum dots embedded in aluminum gallium arsenide (AlGaAs), fabricated by the droplet epitaxy method were used. This method was originally developed by NIMS. As a distinctive feature of the quantum dots, the length of the crystal lattice is perfectly matched between the guest and host materials. As a result, an unprecedented clean quantum structure was realized. We succeeded in observation of charged excitons by measuring the photon emission signals from single quantum dots. In particular, when the stabilization energy of charged excitons was compared with that of a quantum well structure of the same type of material, which was previously known to be ~1 meV, it was found to have a value more than 10 times larger.

This increase in many-body energy is due to a remarkable increase in the Coulomb force between in the many-particle system resulting from packing electrons in a 3-dimensional nano-space. This result elucidates for the first time the effect of confinement of a multi-electron state in a nano-space, which had not been known in the past, and thus is a result with extremely large scientific impact. From the viewpoint of applied technology, because electron correlation is also the source of diverse types of non-linear effect devices such as optical switching devices and lasers, if interaction intensity can be controlled using nanostructures, this can be expected to lead to the development of optical semiconductor devices which enable stable drive with low power consumption.

This result was published in the American scientific journal, Physical Review B, Vol. 82, Issue 20, Page 201301(R) (Nov. 15, 2010, DOI: 10.1103/PhysRevB.82.201301) under the title: Energy renormalization of exciton complexes in GaAs quantum dots, by M. Abbarchi et al.

For more information:

Takashi Kuroda
Nanophotonics Group, Quantum Dot Research Center
National Institute for Materials Science
TEL +81-29-860-4194
E-mail: kuroda.takashi@nims.go.jp

Mikiko Tanifuji | Research asia research news
Further information:
http://www.nims.go.jp/laser_kuroda
http://www.nims.go.jp
http://www.researchsea.com

More articles from Materials Sciences:

nachricht A new tool for discovering nanoporous materials
23.05.2017 | Ecole Polytechnique Fédérale de Lausanne

nachricht Did you know that packaging is becoming intelligent through flash systems?
23.05.2017 | Heraeus Noblelight GmbH

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>