NTT Basic Research Laboratories

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Multidisciplinary Materials Design and Science Laboratory
Advanced Applied Physical Science Laboratory
Quantum Science and Technology Laboratory
Nanophotonics Center
Research Center for Theoretical Quantum Physics
October 31, 2001

Semiconductor ferromgnet in a quantum-dot artificial crystal

We predict that a quantum-dot lattice is formed in a quantum wire network and exhibits ferromagnetism. A theoretical calculation based on a local spin density approximation shows that quantum dots can be formed on the crossings of 0.104 micrometer-wide InAs quantum wires, which form a Kagome lattice having a flat band. This dot lattice has the ferromagnetic ground state when the flat band is half-filled, even though it contains no magnetic elements. We also demonstrate that the ferromagnetism can be turned on and off in a controllable manner by changing the electron filling.
[Reference: Applied Physics Letters 78, 3702 (2001).]

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