AsianScientist (Oct. 28, 2014) – A group of researchers from the University of Tokyo have become the first to experimentally prove the Kondo effect, a prediction first made in the field of electron physics 40 years ago. Their findings have been published in Physical Review Letters.
The Kondo effect, first proposed theoretically 1964, describes a phenomenon involving magnetic impurities in a metal. Even a single magnetic atom in a metal can cause the free electrons around it to also become magnetized. When this metal is cooled to sub-zero temperatures, the atom enters the scenario described by the problem of Schrödinger’s cat: existing in multiple quantum states simultaneously. Consequently, the electron cloud ends up magnetized in two different directions, both of which can be considered the north-pole points.
An electron scattered off the Kondo state preserves its spin because the localized magnetic moment is screened, but it acquires a so-called π/2 phase shift in the wave function; this can be viewed as a fingerprint of screening effect by the electron cloud. This π/2 phase shift predicted about 40 years ago is considered to be a hallmark of the Kondo effect. Numerous experimental attempts to observe have thus far failed due to technical difficulties.
An international team of researchers, led by Dr. Shintaro Takada at the University of Tokyo, have succeeded in observing the Kondo π/2 phase shift for the first time, thus experimentally confirming the Kondo effect.
They used a device known as a two-path interferometer, which enables detection of the electron scattering phase with great precision. Interferometers are used in many fields, including optics and astronomy, to measure the either characteristics of waves such as light, sound and radio, or the materials which transmit, reflect or refract those waves.
The study authors hope their results lead to further insights in the research of electronic properties in solids.
The full article can be found at: Takada et al. (2014) Transmission phase in the Kondo regime revealed in a two-path interferometer.
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Source: University of Tokyo
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