  Strong magnetic fields at plasma-plasma interfaces can be naturally produced
in laser-plasma interactions. Using theoretical analysis and fully
three-dimensional particle-in-cell simulations, we demonstrate that
relativistic topological waves can be generated via Cherenkov and Doppler
resonances in the interaction of intense femtosecond laser pulses with
near-critical-density plasmas. At the self-magnetized plasma-plasma interface,
a new slow-wave branch appears. Its phase velocity is much smaller than the
group velocity of the laser pulse and the electron beam velocity. Therefore,
the Cherenkov resonance condition can be easily satisfied. Furthermore, since
electrons undergo betatron oscillations, Doppler resonances may also occur and
are responsible for the excitation of several frequency-shifted branches
observed in our simulations. After the passage of the laser pulse, we observe a
fast remnant mode with relativistic amplitude and frequency close to the local
plasma frequency. This mode continues to accelerate electrons further for many
tens of laser periods even after the laser pulse has left the plasma.
