  It has been suggested that a zero-bias conductance peak in quantum wires
signifies the presence of Kondo spin-correlations, which might also relate to
an intriguing 1D spin-effect known as the 0.7 structure. These zero-bias
anomalies (ZBA) are strongly temperature dependent, and have been observed to
split into two peaks in magnetic field, both signatures of Kondo correlations
in quantum dots. We present data in which ZBAs in general do not split as
magnetic field is increased up to 10 T. A few of our ZBAs split in magnetic
field but by significantly less than the Kondo splitting value, and evolve back
to a single peak upon moving the 1D constriction laterally. The ZBA therefore
does not appear to have a Kondo origin, and instead we propose a simple
phenomenological model to reproduce the ZBA which is in agreement mostly with
observed characteristics.
