Nature of isomerism in exotic sulfur isotopes

We clarify the origin of the anomalously hindered $E2$ decay from the $4^+_1$ level in $^{44}$S by performing a novel many-body analysis in the shell model. Within a unified picture about the occurrence of isomerism in neutron-rich sulfur isotopes, the $4^+_1$ state is demonstrated to be a $K=4$ isomer dominated by the two-quasiparticle configuration $\nu\Omega^{\pi}=1/2^-\otimes\nu\Omega^{\pi}=7/2^-$. The $4^+_1$ state in $^{44}$S is a new type of high-$K$ isomer which has significant triaxiality.