Leo Esaki

Leo Esaki is a Japanese physicist who shared the 1973 Nobel Prize in Physics for discovering electron tunneling in semiconductors, demonstrated with the Esaki diode.

Quantum tunneling: A quantum process in which a particle crosses a barrier it could not surmount in classical physics. Esaki showed that electrons tunnel through a thin semiconductor junction barrier.
Sony: A Japanese multinational company founded in 1946 that developed and marketed consumer electronics and semiconductor devices. Esaki conducted his pioneering semiconductor research at Sony’s predecessor, Tokyo Tsushin Kogyo.
Nobel Prize in Physics: An annual award recognizing outstanding contributions to physics, established by the will of Alfred Nobel. Esaki shared the 1973 award for experimental discoveries concerning tunneling phenomena in semiconductors and superconductors.
Tunnel diode oscillator: An electronic oscillator that uses a tunnel diode’s negative differential resistance to sustain oscillations. It converts the diode behavior Esaki discovered into a source of high-frequency signals.
Quantum electronics: The study and engineering of electronic devices whose operation depends on quantum-mechanical effects. Esaki’s diode showed that quantum tunneling could be harnessed in a practical semiconductor device.
Esaki diode: A heavily doped semiconductor diode whose current-voltage curve includes a region of negative differential resistance. This device provided the experimental demonstration behind Esaki’s Nobel-recognized discovery.
Tokyo Tsushin Kogyo: The Japanese electronics company founded in 1946 that later became Sony. Esaki worked there when he discovered tunneling in heavily doped germanium.
IBM: An American technology company whose research organization has made contributions to computing and the physical sciences. Esaki joined IBM’s Thomas J. Watson Research Center and later directed it.
Microwave electronics: The design and use of electronic circuits operating at microwave frequencies. Tunnel diodes were used in circuits where their rapid response could support microwave-frequency operation.
Scanning tunneling microscope: An instrument that maps surfaces by measuring quantum tunneling current between a sharp tip and a sample. Its operation uses tunneling as a measurable signal, a broader technological legacy of Esaki’s discovery.

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IBM ResearchRelated: Esaki's IBM research on tunneling devices expanded the laboratory's influence in condensed-matter physics.