Bose Einstein Condensate - BEC

Bose Einstein condensate (BEC), a defined as a state of matter, in which separate subatomic particles or atoms, cooled to approximately absolute zero (0 K, − 459.67 °F or − 273.15 °C; K = kelvin), coalesce into an entity of single quantum mechanical. It means one that can be defined by a wave function - on a near-macroscopic scale. This matter form was predicted by Albert Einstein in 1924 based on the quantum formulations of the Indian physicist named Satyendra Nath Bose.

More about Bose Einstein Condensate

Although this had been predicted for decades, the first atomic BEC was formed only in 1995, when Carl Wieman and Eric Cornell of JILA, a research institute operated jointly by the NIST (National Institute of Standards and Technology) and the University of Colorado at Boulder, cooled rubidium atom gas to 1.7 × 10⁻⁷ K more than absolute zero. Including Wolfgang Ketterle of the MIT - Massachusetts Institute of Technology, who created a BEC with sodium atoms, these researchers have received the 2001 Nobel Prize for Physics. BEC research has expanded the quantum physics understanding and has led to the discovery of new physical effects.

Traces back to 1924, BEC theory, when Bose considered how photon groups behave. Photons belong to the two great classes of submicroscopic or elementary particles described by whether their quantum spin is an odd half-integer (1/2, 3/2, …) or non-negative integer (0, 1, 2, …). The former type, known as bosons, includes photons, whose spin is given as 1. The latter type, which is fermions, includes electrons, whose spin is given as 1/2.

As noted by Bose, the two classes behave in a different way, noticed in Fermi-Dirac and Bose-Einstein statistics. As Pauli's exclusion principle says, fermions tend to avoid each other, for which reason every electron in a group occupies a separate quantum state (which is indicated by different quantum numbers, like an electron's energy). In contrast, an unlimited count of bosons may contain similar energy states and share a single quantum state.

BECs Are Related to Two Remarkable Phenomena of Low-Temperature 

This happens due to superfluidity, where each of the helium isotopes 3He and 4He produces a liquid that flows with zero friction, and superconductivity, where electrons move through a material with zero electrical resistance. The 4He atoms are bosons, and although 3He electrons and atoms are fermions, they can also undergo Bose condensation if they pair-up with the opposite spins to produce boson-like states with zero net spins. Deborah Jin, including her colleagues in 2003 at JILA have used paired fermions to create the first atomic fermionic condensate.

The research of BEC has yielded new optical and atomic physics, like the atom laser Ketterle demonstrated in the year 1996. A conventional light laser emits coherent photon beams; they are all exactly in phase and are focused on an extremely small, bright spot. In the same way, an atom laser forms a coherent beam of atoms that is focused at high intensity. Potential applications are more-accurate atomic clocks and enhanced techniques to manufacture integrated circuits and electronic chips.

BEC's most intriguing property is, it can slow downlight. In 1998, Lene Hau of Harvard University, including her colleagues, slowed light travelling through a BEC from its speed in the vacuum of 3 × 10⁸ meters per second to a mere of 17 meters per second, or up to 38 miles per hour. From then, Hau and others have completely stored and halted a light pulse within a BEC, later releasing the light unchanged or sending it to the second BEC. These manipulations hold promise for newer light-based telecommunication types, quantum computing, and optical storage of data, though the low-temperature requirements of BECs offer practical difficulties.

Experimental Observation

In 1938, John Allen, Don Misener, and Pyotr Kapitsa discovered that helium-4 became a new kind of fluid, which, now called superfluid, at temperatures below 2.17 K (which is the lambda point). Superfluid helium has several unusual properties, including zero viscosity (which is the ability to flow with no dissipating energy) and the quantized vortices' existence. Also, it was quickly believed that the superfluidity was because of the partial Bose-Einstein condensation of the liquid.

Several properties of superfluid helium appear in the gaseous condensates, which are created by Wieman and Ketterle, Cornell. Superfluid helium-4 is considered a liquid rather than a gas. This means the interactions between the atoms are said as relatively strong; the original Bose-Einstein condensation theory should be heavily modified to describe it. However, Bose-Einstein condensation remains fundamental to the superfluid helium-4 properties. It should also be noted that a fermion, helium-3, which also enters into a superfluid phase (at a very lower temperature), can be explained by the formation of the bosonic Cooper pairs of two atoms.