  With their incomparable time-frequency accuracy, frequency combs have
significantly advanced precision spectroscopy, ultra-sensitive detection, and
atomic clocks. Traditional methods to create photonic, phononic, and magnonic
frequency combs hinge on material nonlinearities which are often weak,
necessitating high power densities to surpass their initiation thresholds,
which subsequently limits their applications. Here, we introduce a novel
nonlinear process to efficiently generate magnonic frequency combs (MFCs) by
exploiting exceptional points (EPs) in a coupled system comprising a
pump-induced magnon mode and a Kittel mode. Even without any cavity, our method
greatly improves the efficiency of nonlinear frequency conversion and achieves
optimal MFCs at low pump power. Additionally, our novel nonlinear process
enables excellent tunability of EPs using the polarization and power of the
pump, simplifying MFC generation and manipulation. Our work establishes a
synergistic relationship between non-Hermitian physics and MFCs, which is
advantages for coherent/quantum information processing and ultra-sensitive
detection.
