  In this study, we address the phase coherent transport in a
sub-micrometer-sized Hall bar made of epitaxial Bi2Se3 thin film by probing the
weak antilocalization (WAL) and the magnetoresistance fluctuation below 22 K.
The WAL effect is well described by the Hikami-Larkin-Nagaoka model, where the
temperature dependence of the coherence length indicates that electron
conduction occurs quasi-one-dimensionally in the narrow Hall bar. The
temperature-dependent magnetoresistance fluctuation is analyzed in terms of the
universal conductance fluctuation, which gives a coherence length consistent
with that derived from the WAL effect.
