Observation of a near-threshold enhancement in the $\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ mass spectrum from $e^{+}{e}^{-}\to \varphi \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ at $\sqrt{s}$ from 3.51 to 4.60 GeV

The process $e^{+}{e}^{-}\to \varphi \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ is studied using data samples collected with the BESIII detector at the BEPCII collider at center-of-mass energies $\sqrt{s}$ ranging from $3.51$ to $4.60\mathrm{G}\mathrm{e}\mathrm{V}$ . An intermediate resonance structure is observed near the threshold of $\Lambda \bar{\Lambda}$\mathrm{.}Ithasamassof$(2262 \pm 4 \pm 28)~{\rm{MeV}}/c^{2}$ and a width of $(72\pm 5\pm 43)\mathrm{M}\mathrm{e}\mathrm{V}$, where the quoted uncertainties are statistical and systematic, respectively. The $J^{PC}$ quantum numbers of $0^{-+}$ and $0^{++}$ are rejected, while other $J^{PC}$ hypotheses are possible, according to the helicity angle study. The energy-dependent cross section of the $e^{+}{e}^{-}\to \varphi \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ process is measured for the first time in this energy region, and contributions from excited $\psi$ states and vector charmonium-like $Y$-states are investigated.