  Nonlocal spin polarization phenomena are thoroughly investigated in the
devices made of chiral metallic single crystals of CrNb$_3$S$_6$ and NbSi$_2$
as well as of polycrystalline NbSi$_2$. We demonstrate that simultaneous
injection of charge currents in the opposite ends of the device with the
nonlocal setup induces the switching behavior of spin polarization in a
controllable manner. Such a nonlocal spin polarization appears regardless of
the difference in the materials and device dimensions, implying that the
current injection in the nonlocal configuration splits spin-dependent chemical
potentials throughout the chiral crystal even though the current is injected
into only a part of the crystal. We show that the proposed model of the spin
dependent chemical potentials explains the experimental data successfully. The
nonlocal double-injection device may offer significant potential to control the
spin polarization to large areas because of the nature of long-range nonlocal
spin polarization in chiral materials.
