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 Decoding cement's shape promises greener concrete
08.12.2016 | Rice University

nachricht Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D
08.12.2016 | DOE/Brookhaven National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>