Efimov state
Encyclopedia
The Efimov effect is an effect in the quantum mechanics
of Few-body systems
predicted by the Soviet theoretical physicist V. N. Efimov
in 1970. Efimov’s effect refers to a scenario in which three identical boson
s interact, with the prediction of an infinite series of excited three-body energy levels when a two-body state is exactly at the dissociation threshold. One corollary is that there exist bound states (called Efimov states) of three bosons even if the two-particle attraction is too weak to allow two bosons to form a pair.
In 2005, for the first time the research group of Rudolf Grimm
und Hanns-Christoph Nägerl from the Institute of experimental physicists (University of Innsbruck, Austria) experimentally confirmed such a state in an ultracold gas of caesium
atoms. In 2006 they published their findings in the scientific journal Nature.
Further experimental proof for the existence of Efimov state has been given recently by independent groups.. The characteristic universal scaling factor (22.7) of the states has also been confirmed almost 40 years after Efimov's purely theoretical prediction.
The interest in the "universal phenomena" of cold atomic gases is still growing, especially because of the long waited experimental results. The discipline of universality in cold atomic gases nearby the Efimov states are sometimes commonly referred to as "Efimov physics".
The unusual Efimov state has an infinite number of similar states. These states are completely identical except that their sizes and energy level
s scale by a universal factor of 22.7 (in the case of three identical bosonic particles).
The Efimov states are independent of the underlying physical interaction, and can in principle be observed in all quantum mechanical systems (molecular, atomic, and nuclear).
The states are very special because of their "non-classical" nature: The size of each three particle Efimov state is much larger than the force-range between the individual particle pairs. This means that the state is purely quantum mechanical. Similar phenomena are observed in two-neutron halo-nuclei, such as lithium-11. (Halo nuclei could be seen as special Efimov states, depending on the subtle definitions.)
A (three-particle) Efimov state where the (two-body) sub-systems are unbound, are often depicted symbolically by the Borromean rings
. This means that if one of the particles are removed, the remaining two fall apart. In this case the Efimov state is also called a Borromean state.
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...
of Few-body systems
Few-body systems
In quantum mechanics and classical mechanics, a few-body system consists of a small number of well-defined structures or point particles.In quantum mechanics, examples of few-body systems include light nuclear systems , small molecules, light atoms , atomic collisions, and quantum...
predicted by the Soviet theoretical physicist V. N. Efimov
Vitaly Efimov
Vitaly N. Efimov is a Russian theoretical physicist. He proposed the existence of a novel and exotic state of matter now dubbed the Efimov State as a researcher in A.F...
in 1970. Efimov’s effect refers to a scenario in which three identical boson
Boson
In particle physics, bosons are subatomic particles that obey Bose–Einstein statistics. Several bosons can occupy the same quantum state. The word boson derives from the name of Satyendra Nath Bose....
s interact, with the prediction of an infinite series of excited three-body energy levels when a two-body state is exactly at the dissociation threshold. One corollary is that there exist bound states (called Efimov states) of three bosons even if the two-particle attraction is too weak to allow two bosons to form a pair.
In 2005, for the first time the research group of Rudolf Grimm
Rudolf Grimm
Rudolf Grimm is an experimental physicist from Austria. His work centres on ultracold atoms and quantum gases. He was the first scientist worldwide who, with his team, succeeded in realizing a Bose-Einstein condensation from molecules.-Career:Grimm graduated in physics from the University of...
und Hanns-Christoph Nägerl from the Institute of experimental physicists (University of Innsbruck, Austria) experimentally confirmed such a state in an ultracold gas of caesium
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
atoms. In 2006 they published their findings in the scientific journal Nature.
Further experimental proof for the existence of Efimov state has been given recently by independent groups.. The characteristic universal scaling factor (22.7) of the states has also been confirmed almost 40 years after Efimov's purely theoretical prediction.
The interest in the "universal phenomena" of cold atomic gases is still growing, especially because of the long waited experimental results. The discipline of universality in cold atomic gases nearby the Efimov states are sometimes commonly referred to as "Efimov physics".
The unusual Efimov state has an infinite number of similar states. These states are completely identical except that their sizes and energy level
Energy level
A quantum mechanical system or particle that is bound -- that is, confined spatially—can only take on certain discrete values of energy. This contrasts with classical particles, which can have any energy. These discrete values are called energy levels...
s scale by a universal factor of 22.7 (in the case of three identical bosonic particles).
The Efimov states are independent of the underlying physical interaction, and can in principle be observed in all quantum mechanical systems (molecular, atomic, and nuclear).
The states are very special because of their "non-classical" nature: The size of each three particle Efimov state is much larger than the force-range between the individual particle pairs. This means that the state is purely quantum mechanical. Similar phenomena are observed in two-neutron halo-nuclei, such as lithium-11. (Halo nuclei could be seen as special Efimov states, depending on the subtle definitions.)
A (three-particle) Efimov state where the (two-body) sub-systems are unbound, are often depicted symbolically by the Borromean rings
Borromean rings
In mathematics, the Borromean rings consist of three topological circles which are linked and form a Brunnian link, i.e., removing any ring results in two unlinked rings.- Mathematical properties :...
. This means that if one of the particles are removed, the remaining two fall apart. In this case the Efimov state is also called a Borromean state.