Overview of Material Science Research

Hideaki Takayanagi
Materials Science Laboratory

@The Materials Science Laboratory (MSL) aims at producing new materials by controlling the arrangement and coupling among atoms and molecules. By producing such materials, MSL also aims to discover new quantum phenomena and to create new concepts. Toward these goals, the following four MSL groups investigate a wide variety of materials, from inorganic matter, such as semiconductors, to organic matter, such as neurotransmitters. The important feature of MSL is the effective sharing of nanofabrication and measurement techniques developed originally in each group.

Molecular and Bio-Science Research Group
Creating new organic materials based on the manipulation of single molecules, and researching information processing devices based on neural functions.

Superconducting Thin Films Research Group
Creating new high-Tc superconductors and applications to microwave communication using the molecular beam epitaxy method.

Superconducting Quantum Physics Research Group
Creating a quantum computer using superconductor, and creating new magnetic devices using quantum dot arrays.

Spintronics Research Group
Controlling the spin degree of freedom in a semiconductor and achieving new device functions in future electronics.
The four major results obtained in fiscal year 2001 are as follows.
1. The neuronal responses in rat hippocampus induced by low magnesium content. By measuring the spatial distribution of electrical activities using a special microelectrode array, it is found that electrical bursts became highly active in a magnesium-free medium. This indicates that magnesium ion could play a major role of neural activities in rat hippocampus.
2. In-situ MgB2 thin film growth by the molecular beam epitaxy (MBE) method. MgB2 has the highest superconducting transition temperature among non-oxide materials and is a promising for applications. The in-situ growth of MgB2 films without annealing at elevated temperatures is substantial progress toward the fabrication of Josephson junctions.
3. A single shot readout of states in a flux quantum bit (qubit) with a superconductor ring. This could be the basis for the creation of a quantum computer using superconductor. The readout of the states is performed with sufficient accuracy by a DC-SQUID (superconductor quantum interferometer) aligned closely to the qubit.
4. A novel spin-filter device that has almost 100 % spin-filtering efficiency. The proposed device consists of a triple-barrier structure made up of nonmagnetic semiconductors. Electrons with a specific spin state are extracted by adjusting the emitter-collector bias voltage.
The details of these accomplishments will be described in the following pages.