Fig. 2
From: Observation of spin–orbit coupling induced Weyl points in a two-electron double quantum dot
Detecting magnetic Weyl points through the conductance of a two-electron double quantum dot. a Device layout, showing the nanowire (black), and the metallic electrodes (gold) including the contacts NL, NR, and the finger gates below the nanowire. The gate-controlled electric double-well potential (red) confines one electron (blue) in each well. b Charge stability diagram: zero-bias conductance at zero magnetic field as a function of two gate voltages. Labels such as (1,1) specify the number of electrons on each dot. c Finite-bias differential conductance at zero magnetic field along the dotted horizontal line in b at VgR = 0.236 V, indicating an exchange splitting ΔE ≈ J0 ≈ 0.055 meV. The white curve shows a cut along the vertical dotted line at VgL = 0.526 V. d–f Magnetic-field dependence of the finite-bias conductance in the (1,1) charging state. d Data taken in a generic direction (here θ = 60° and ϕ = 90°) exhibit no ground-state degeneracy. Solid gray lines are ground-state energy gaps obtained from theoretical fits (see Methods). e In the “sweet” direction, θ ≈ 130° and ϕ ≈ 90°, a ground-state degeneracy (a magnetic Weyl point) emerges at B ≈ 70 mT. f θ dependence of the gap for ϕ = 90° and a magnetic field very close to the Weyl point, B = 75 mT ≈ B0. Time-reversed Weyl points emerge at θ ≈ 130° and θ ≈ 310°. g Visualization of the calculated ground-state Berry curvature vector field in the vicinity of the two magnetic Weyl points (red). The outward oriented hedgehog patterns indicate that the two Weyl points carry the same topological charge. h Magnetic-field and θ dependence of the zero-bias magnetoconductance, ΔG(B) = G(B) − G(B = 0) along the lines indicated on the left sketch by colored lines. The maximum at B ≈ 70 mT in the bottom right panel indicates a magnetic Weyl point, also marked on the surface of the sphere
