Scalarized Kerr-Newman Black Holes

Abstract: In this paper, we construct scalarized rotating black holes within the framework of Einstein-Maxwell-scalar models. These models incorporate non-minimal couplings that can induce tachyonic instabilities, leading to the spontaneous scalarization of Kerr-Newman (KN) black holes. By exploring the domain of existence, we observe that the presence of scalarized KN black holes is suppressed by the black hole spin, with a maximum spin threshold beyond which scalarized solutions cease to exist. Intriguingly, we find that in specific parameter regimes, scalarized KN black holes can exhibit the presence of two unstable and one stable light rings on the equatorial plane, manifesting in both prograde and retrograde directions.