  The nodal-line semimetals have attracted immense interest due to the unique
electronic structures such as the linear dispersion and the vanishing density
of states as the Fermi energy approaching the nodes. Here, we report
temperature-dependent transport and scanning tunneling microscope
(spectroscopy) (STM[S]) measurements on nodal-line semimetal ZrSiSe.Our
experimental results and theoretical analyses consistently demonstrate that the
temperature induces Lifshitz transitions at 80 and 106 K in ZrSiSe, which
results in the transport anomalies at the same temperatures. More strikingly,
we observe a V-shaped dip structure around Fermi energy from the STS spectrum
at low temperature,which can be attributed to co-effect of the spin-orbit
coupling and excitonic instability. Our observations indicate the correlation
interaction may play an important role in ZrSiSe, which owns the
quasi-two-dimensional electronic structures.
