  Unconventional quantum states, most notably the two-dimensional (2D)
superconductivity, have been realized at the interfaces of oxide
heterostructures where they can be effectively tuned by the gate voltage
($V_G$). Here we report that the interface between high-quality EuO (111) thin
film and KTaO3 (KTO) (110) substrate shows superconductivity with onset
transition temperature $T_c^{onset}$ = 1.35 K. The 2D nature of
superconductivity is verified by the large anisotropy of the upper critical
field and the characteristics of a Berezinskii-Kosterlitz-Thouless transition.
By applying $V_G$, $T_c^{onset}$ can be tuned from ~ 1 to 1.7 K; such an
enhancement can be possibly associated with a boosted spin-orbit energy
${\epsilon}_{so}$ = $\hbar$ / ${\tau}_{so}$, where ${\tau}_{so}$ is the
spin-orbit relaxation time. Further analysis of ${\tau}_{so}$ based on the
upper critical field ($H_{c2}$) and magnetoconductance reveals complex nature
of spin-orbit coupling (SOC) at the EuO/KTO(110) interface with different
mechanisms dominate the influence of SOC effects for the superconductivity and
the magnetotransport in the normal state. Our results demonstrate that the SOC
should be considered as an important factor determining the 2D
superconductivity at oxide interfaces.
