Fig. 1
From: Observation of spin–orbit coupling induced Weyl points in a two-electron double quantum dot
Geometries of degeneracy points for simple spin systems in a Zeeman field. a–c A single spin-1/2. d–f Two interacting S = 1/2 spins with isotropic antiferromagnetic exchange. g–i Two interacting S = 1/2 spins subject to spin–orbit interaction, where μB is the Bohr magneton, B is the magnetic field, S, SL/R are the spin operators, \(g\), \(\widehat {\mathbf{g}}_{{\mathrm{L}}/{\mathrm{R}}}\) are the corresponding g-factors/g-tensors, and \(J\) and \(\widehat {\mathbf{J}}\) are the exchange coupling between the spins. b, e, h, Characteristic magnetic-field dependence of the energy spectrum, T are the triplets, and S is the singlet solution. Red dots mark the ground-state degeneracy points. c, f, i, Geometry of the magnetic-field values where the ground state is degenerate
