BEC Excitement Beckons While Physics Redux Strings Along

摘要

Observations of collective excitations in Bose-Einstein condensates have propelled papers #6 and #8 into the Top Ten for the first time. Bose-Einstein condensation (BEC) is a phenomenon in which a macroscopic number of atoms end up in the ground state of an ultracold magnetic trap. The macroscopic system exhibits quantum behavior: it is a coherent state of matter that relates to "normal" matter as laser light relates to "normal" light. At MIT, Wolfgang Ketterle's group first detected BEC in 1995 by turning off the trapping fields suddenly and looking at the velocity spectrum of sodium atoms as they flew out of the trap. BEC provides the theoretical basis for understanding superfluidity in liquid helium and superconductivity in metals. However, these systems have strong interactions between their constituent particles which alter the features of the BEC and make theoretical progress difficult. Dilute gas BEC is a much better environment for exploring the quantum behavior of the "fifth state" of matter.