  The ZrSiS-type compounds are Dirac semimetals and have been attracting
considerable interest in recent years due to their topological electronic
properties and possible applications. In particular, gapped Dirac nodes can
possess large spin Berry curvatures and thus give rise to large spin Hall
effect (SHE) and spin Nernst effect (SNE), which may be used to generate pure
spin current for spintronics and spin caloritronics without applied magnetic
field or magnetic material. In this paper we study both SHE and SNE in ZrXY (X
= Si, Ge; Y = S, Se, Te) based on \textit{ab initio} relativistic band
structure calculations. Our theoretical calculations reveal that some of these
compounds exhibit large intrinsic spin Hall conductivity (SHC) and spin Nernst
conductivity (SNC). The calculated SHC of ZrSiTe is as large as -755
($\hbar$/e)(S/cm). Since the electric conductivity of these Dirac semimetals
are much smaller than that of platinum which has the largest intrinsic SHC of
$\sim$2200 ($\hbar$/e)(S/cm), this indicates that they will have a larger spin
Hall angle than that of platinum. Remarkably, we find that both the magnitude
and sign of the SHE and SNE in these compounds can be significantly tuned by
changing either the electric field direction or spin current direction and may
also be optimized by slightly varying the Fermi level via chemical doping.
Analysis of the calculated band- and $k$-resolved spin Berry curvatures show
that the large SHE and SNE as well as their remarkable tunabilities originate
from the presence of many slightly spin-orbit coupling-gapped Dirac nodal lines
near the Fermi level in these Dirac semimetals. Our findings suggest that the
ZrSiS-type compounds are promising candidates for spintronic and spin
caloritronic devices, and will certainly stimulate further experiments on these
Dirac semimetals.
