Heavy-quark spin polarization induced by the Kondo effect in a magnetic field

We propose a new mechanism of the heavy-quark spin polarization (HQSP) in quark matter induced by the Kondo effect under an external magnetic field. The Kondo effect is caused by a condensate between a heavy and a light quark called the Kondo condensate leading to a mixing of the heavy- and light-quark spins. Thus, the HQSP is driven through the Kondo effect from light quarks coupling with the magnetic field in quark matter. For demonstration, we employ the Nambu-Jona-Lasinio type model under a magnetic field and investigate the HQSP within the linear response theory with vertex corrections required by the U(1)EM electromagnetic gauge invariance. As a result, we find that the HQSP arises significantly with the appearance of the Kondo effect. Our findings are testable in future sign-problem-free lattice simulations.