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
From ancient fossils to future cars
21.10.2016 | University of California - Riverside
Study explains strength gap between graphene, carbon fiber
20.10.2016 | Rice University
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences