It is notable that along the $N=Z$ line in the nuclear chart, extremely large collectivity emerges suddenly in the mass-80 region. By applying the Monte Carlo shell model (MCSM) and the Hartree-Fock-Bogolyubov plus generator coordinate method (HFB+gcm), we study this problem to find the origin. On the basis that both calculations reproduce the experimental data of the $N\approx Z$ nuclei with $A=64\sim 88$, we identify the backbone from full shell-model calculations that can explain the strong prolate deformation. We find that inclusion of the $2d_{5/2}$ orbit in the model space to cooperate with $1g_{9/2}$ is the key ingredient to describe the rapid increase of collectivity from ⁷⁰Se to ⁷⁶Sr and to produce the observed large $B(E2)$ values in ⁷⁶Sr, ⁷⁸Sr and ⁸⁰Zr. The quadrupole-quadrupole (QQ) interaction acting between the quasi-SU(3) partner orbits, $1g_{9/2}-2d_{5/2}$, is the driving force that changes the nuclear shape from oblate- to prolate-deformed. We further suggest that the quasi-SU(3) effect is particularly amplified in the $N\approx Z$ nuclei because these are the unique examples where quasi-SU(3) partner orbits can be formed, like the nuclear pairing, simultaneously in three different types: neutron-neutron (n-n), proton-proton (p-p), and neutron-proton (n-p), which respectively interact through the n-n, p-p, and n-p components of the QQ force to enhance the quadrupole collectivity coherently.

值得注意的是 $ñ=ž$在核图中的直线上，在质量80区突然出现了巨大的集体。通过应用蒙特卡洛壳模型（MCSM）和Hartree-Fock-Bogolyubov加生成器坐标法（HFB + gcm），我们研究了此问题以找到原点。在这两个计算基础上重现了实验的数据。$ñ\approx ž$ 核与 $\mathrm{一种}=64〜88$，我们从完整的壳模型计算中识别出骨架，这可以解释强烈的扁形变形。我们发现$\mathrm{2个}{d}_{5/\mathrm{2个}}$ 在模型空间中运行以与 $\mathrm{1个}{G}_{9/\mathrm{2个}}$是描述从⁹⁰ Se到⁷⁶ Sr的集体快速增加并产生所观察到的大颗粒的关键成分$乙（E\mathrm{2个}）$值分别为⁷⁶ Sr，⁷⁸ Sr和⁸⁰ Zr。在准SU（3）伙伴轨道之间起作用的四极-四极（QQ）相互作用，$\mathrm{1个}{G}_{9/\mathrm{2个}}-\mathrm{2个}{d}_{5/\mathrm{2个}}$是将核形状从扁形变形变为扁形变形的驱动力。我们进一步建议准SU（3）效应在$ñ\approx ž$原子核，因为它们是可以同时形成三种类型的准SU（3）伙伴轨道（如核对）的独特例子：中子-中子（nn），质子-质子（pp）和中子-质子（ np），它们分别通过QQ力的nn，pp和np分量相互作用，从而相干地增强了四极子的整体性。