  An analytical theory for the surface-enhanced Raman optical activity (SEROA)
with the magnetic response of the substrate particle has been presented. We
have demonstrated that the SEROA signal is proportional to the magnetic
polarizability of the substrate particle, which can be significantly enhanced
due to the existence of the magnetic response. At the same time, a large
circular intensity difference (CID) for the SEROA can also be achieved in the
presence of the magnetic response. Taking Si nanoparticles as examples, we have
found that the CID enhanced by a Si nanoparticle is 10 times larger than that
of Au. Furthermore, when the molecule is located in the hotspot of a Si dimer,
CID can be 60 times larger. The phenomena originate from large magnetic fields
concentrated near the nanoparticle and boosted magnetic dipole emission of the
molecule. The symmetric breaking of the electric fields caused by the magnetic
dipole response of the nanoparticle also plays an important role. Our findings
provide a new way to tailor theRaman optical activity by designing
metamaterials with the strong magnetic response.
