Thermal quantum physics in Lineland

Posted: Sunday, 9 March 2008

From left: Philipp Wicke, Aaldert van Amerongen, Klaasjan van Druten, and Jan-Joris van Es.

A team of researchers from the Netherlands and Australia (A. H. van Amerongen, J. J. P. van Es, P. Wicke, and N. J. van Druten of the University of Amsterdam, and K. V. Kheruntsyan of the University of Queensland node of the ARC Centre of Excellence for Quantum-Atom Optics) has succeeded in comparing the temperature and the density of a one-dimensional quantum gas to an exact theory that was developed back in 1969 by Nobel Laureate C. N. Yang and his brother C. P. Yang.

The results are published in the 7 March issue of the Physical Review Letters [Phys. Rev. Lett. 100, 090402 (2008)] and were selected as Editors' Suggestion as a means of promoting reading across fields.

Karen V. Kheruntsyan

The experiments in Amsterdam were performed using an 'atom chip' a lithographically produced pattern of gold wires on a silicon substrate. By sending currents through the wires, a gas of rubidium atoms is magnetically trapped and cooled to the point where the atoms can only move in one dimension. The atoms thus live in 'Lineland'. The needle-shaped atomic cloud, with a width less than a percent of a human hair, is cooled to temperatures down to 100 nanokelvin.

In this way, the first direct comparison was made possible between experiment and the nearly 40 years old Yang-Yang theory. The Yang-Yang exact solutions to the one-dimensional Bose gas model at finite temperature were a tour-de-force of mathematical and quantum many-body physics but have never been observed in a real physical system. The experimental techniques of laser cooling and magnetic trapping are now allowing physicists to precisely engineer these model systems in the laboratory.

Atom chip image (courtesy of A.H. van Amerongen, J.J.P. van Es and N.J. van Druten)

In addition, the experiment allowed access to the momentum distribution of the gas. This distribution cannot be directly obtained using the Yang-Yang method and the measurement thus poses a new challenge to theory.

Read full paper: Yang-Yang thermodynamics on an atom chip. A. H. van Amerongen, J. J. P. van Es, P. Wicke, K. V. Kheruntsyan, and N. J. van Druten, Phys. Rev. Lett. 100, 090402 (2008).

Further information: contact Dr Klaasjan van Druten, druten@science.uva.nl, +31 20 525 7118 or +31 642 909496; Dr Karen Kheruntsyan, karen.kheruntsyan@uq.edu.au, +61 7 33653420 or +61 7 33716832.