  Understanding the flow of spins in magnetic layered structures has enabled an
increase in data storage density in hard drives over the past decade of more
than two orders of magnitude1. Following this remarkable success, the field of
'spintronics' or spin-based electronics is moving beyond effects based on local
spin polarisation and is turning its attention to spin-orbit interaction (SOI)
effects, which hold promise for the production, detection and manipulation of
spin currents, allowing coherent transmission of information within a device.
While SOI-induced spin transport effects have been observed in two- and
three-dimensional samples, these have been subtle and elusive, often detected
only indirectly in electrical transport or else with more sophisticated
techniques. Here we present the first observation of a predicted 'spin-orbit
gap' in a one-dimensional sample, where counter-propagating spins, constituting
a spin current, are accompanied by a clear signal in the easily-measured linear
conductance of the system.
