Enhancement of Magnetic Fields in Photoemission Spectroscopy via Halbach Array

Angle-Resolved Photoemission Spectroscopy (ARPES) is a critical tool for mapping electronic structure in solid materials. Integrating magnetic fields into ARPES measurements has been challenging but highly desired, given its potential in visualizing field-driven electronic phenomena in superconductivity, symmetry breakings, and topological effects. Attempts have recently been made towards introducing magnetic fields in ARPES (magneto-ARPES), including using a basic solenoid (Huang et al.) or a magnetized nickel yoke (Ryu et al.). However, reported field strength has been insufficient to induce intrinsic electronic phenomena in materials. In this work, we propose to enhance the magnetic field by using a Halbach array, which is an arrangement of magnets in alternating directions. We used the Ansys Maxwell software to simulate the magnetic fields of various Halbach array designs. Our simulation shows that Halbach arrays can achieve significant enhancement of both the strength and confinement of the magnetic field, which are highly desired in magneto-ARPES designs. By combining the Halbach array design with highly accelerated photoelectrons in X-ray PEEM/LEEM setups, we estimate the overall performance could be up to two orders of magnitude better than with a basic solenoid design. Our proposal provides a new pathway for achieving magneto-ARPES.