Polar Phase of Superfluid 3He: Dirac Lines in the Parameter and Momentum Spaces

Resumo

The time reversal symmetric polar phase of the spin-triplet superfluid ³He has two types of Dirac nodal lines. In addition to the Dirac loop in the spectrum of the fermionic Bogoliubov quasiparticles in the momentum space (p_x, p_y, p_z ), the spectrum of bosons (magnons) has Dirac loop in the 3D space of parameters—the components of magnetic field (H_x,H_y,H_z ). The bosonic Dirac system lives on the border between the type-I and type-II.