Generation of Mega-Gauss Magnetic Vortices in Plasmas

Magnetic fields play an essential role in numerous fields, such as material physics, condensed matter physics, accelerator physics and astrophysics. As these fields rapidly expand, the ability to generate small-scale intense magnetic structures with different topologies becomes increasingly important. Plasma is an attractive medium to generate such structures due to its extraordinary ability to sustain strong currents with microscopic spatial scales. Here, using theory and three-dimensional particle-in-cell simulations, we show that a mega-gauss magnetic vortex with a helical rotating structure can be generated when a relativistic ionization front passes through a Laguerre Gaussian (LG) long-wavelength IR laser pulse with orbital angular momentum (OAM). By changing the OAM mode, the plasma current and thus the topology of the magnetic structure can be controlled. We also show that, by employing an ionization front generated by a superposition of co-propagating, beating short-wavelength LG ionization laser pulses, the topological charge of the magnetic vortex can be further manipulated. This is interesting from a fundamental perspective and important for applications, such as quantum topological system manipulation. This magnetic structure also has the potential to be used as an ultrashort-wavelength and high-amplitude vortical undulator, which would provide ultrashort-wavelength X-ray with OAM in compact systems, with no need for helically bunched electron beams.