Effect of symmetry breaking on Dirac points in topological semimetal EuAgBi

<p>Combining symmetry breaking with topological theory constitutes a promising approach for advancing the understanding and control of topological phase transitions, which calls for experimental evidence from suitable material systems. We investigated Dirac points (DP) in noncentrosymmetric EuAgBi through the breaking of inversion symmetry (P), time-reversal symmetry (T), and sixfold rotational symmetry (C₆), using centrosymmetric BaAgBi as the reference. The analysis of various magnetic structures in EuAgBi achieved by controlling temperature and magnetic field shows that breaking P does not affect the existence of DP; breaking both P and T transforms DP into Weyl points (WP); and despite the reduced symmetry when P, T, and C₆ are all broken, WP remains formally unaffected in the field-induced ferromagnetic phase. Additionally, we have realized the possible coexistence of WP and DP along distinct directions. Furthermore, the noncentrosymmetric (P-broken) DP, previously predicted theoretically but lacking experimental evidence, were observed in paramagnetic EuAgBi using angle-resolved photoemission spectroscopy. Our results provide realistic examples of how distinct topological states can emerge under different symmetry-breaking scenarios.</p>