Leo Esaki


Leo Esaki is a Japanese solid-state physicist who shared the 1973 Nobel Prize in Physics with Ivar Giaever and Brian Josephson for his work on tunneling in semiconductors, which led to his invention of the tunnel diode that exploits this phenomenon. His research was done when he was with Sony. He has also contributed in being a pioneer of semiconductor superlattices.

Education

Leo Esaki was born on March 12, 1925, in Osaka, Japan, and grew up in Kyoto, where he attended the Third Higher School. He then went on to study physics at Tokyo Imperial University, graduating with a B.S. in 1947.

Career and research

Sony

In 1956, Esaki became chief physicist at Tokyo Tsushin Kogyo.
In 1957, Esaki recognized that when the p–n junction width of germanium is thinned, the current–voltage characteristic is dominated by the influence of the tunnel effect. As a result, he discovered that as the voltage is increased, the current decreases inversely, indicating negative resistance.
This discovery was the first demonstration of solid tunneling effects in physics—and it was the birth of the first quantum electronic device, the tunnel diode. He received a Ph.D. from Tokyo Imperial University due to this breakthrough invention in 1959.

IBM

In 1960, Esaki moved to the United States and joined IBM's Thomas J. Watson Research Center, where he was appointed an IBM Fellow in 1967.
In 1969, Esaki predicted that semiconductor superlattices will be formed to induce a differential negative-resistance effect via an artificially one-dimensional periodic structural changes in semiconductor crystals. His unique "molecular-beam epitaxy" thin-film crystal growth method can be regulated quite precisely in ultrahigh vacuum. A 1987 comment by Esaki regarding the original paper notes:

"The original version of the paper was rejected for publication by Physical Review on the referee's unimaginative assertion that it was 'too speculative' and involved 'no new physics.' However, this proposal was quickly accepted by the Army Research Office..."

In 1972, Esaki realized his concept of superlattices in III-V group semiconductors. Later, this concept influenced many fields like metals and magnetic materials.

Later life

In 1992, Esaki returned to Japan, where he subsequently served as President of the University of Tsukuba and of the Shibaura Institute of Technology. Since 2006, he is President of Yokohama College of Pharmacy.
Since the death of Yoichiro Nambu in 2015, Esaki is currently the oldest Japanese Nobel laureate.

Family

Esaki's daughter, Anna Esaki, is married to Craig S. Smith, former Shanghai bureau chief of The New York Times and China bureau chief of The Wall Street Journal.

Esaki's "five don'ts" rules

At the 1994 Lindau Nobel Laureate Meetings, Esaki suggested a list of "five don'ts" which anyone in realizing his creative potential should follow. Two months later, the chairman of the Nobel Committee for Physics Carl Nordling incorporated the rules in his own speech.
  1. Don't allow yourself to be trapped by your past experiences.
  2. Don't allow yourself to become overly attached to any one authority in your field – the great professor, perhaps.
  3. Don't hold on to what you don't need.
  4. Don't avoid confrontation.
  5. Don't forget your spirit of childhood curiosity.

Commemoration

In recognition of three Nobel laureates' contributions, the bronze statues of Shin'ichirō Tomonaga, Leo Esaki, and Makoto Kobayashi were set up in the Central Park of Azuma 2 in Tsukuba in 2015.