EXCITONS IN A QUANTUM-WIRE SUBJECTED TO A MAGNETIC-FIELD

We present variational calculations of the ground-state exciton bindin g energy and exciton radius in a quantum wire subjected to an external magnetic field. The magnetic field squeezes the exciton wave function , causing the binding energy to become very large and increase superli nearly with the field; at the same time, the exciton radius shrinks. T he squeezing is more effective in wider wires, where the exciton wave function is ''softer.'' These results are consistent with recently rep orted experimental observations.