Vortex-Lattice Phases of Superfluid ${}_{}{}^3{}_{}{}^{}He$ in Rapid Rotation

Superfluid ${}^3\mathrm{He}$ in the angular velocity of $0.01{\Omega }_{c2\mathrm{}}\le \Omega \le {\Omega }_{c2\mathrm{}}$ is studied theoretically, where ${\Omega }_{c2\mathrm{}}$ is the upper critical field of order $\left({1-T/T}_c\right)\times {10}^7\mathrm{rad}/\mathrm{s}$. Five different phases have been found in the pressure- $\Omega$ plane. Especially, it is shown that the $A$-phase-core vortex experimentally found in the $B$ phase originates from Schopohl's polar state at ${\Omega }_{c2\mathrm{}}$ via an $A$-phase mixed-twist lattice with polar cores and the normal-core lattice of Ohmi, Tsuneto, and Fujita [Prog. Theor. Phys. 70, 647 (1983)].