Extended Data Fig. 10: Exact diagonalization of exciton relative motion in crossed electric and magnetic fields.

a, Energy of the MLESO as a function of the in-plane electric field strength F_x at B = 0 T. A quadratic dependence with the electric field is observed, as expected from the dc Stark effect. b, The probability density |ψ(r = 0)|², proportional to the exciton oscillator strength, decreases by about 10–15% with increasing electric field F_x. Hence, a decrease in oscillator strength, as seen in the experiment, should primarily arise from COM quantum confinement of excitons. c, d, Calculated probability density |ψ(r)|² for F_x = 0 and F_x = 30 V μm⁻¹, respectively. e, Probability density |ψ(x, y = 0)|² in the direction of the electric field for F_x = 0 (blue) and F_x = 30 V μm⁻¹ (red). The oscillations seen at finite electric field arise from reflections from the finite-sized box assumed in the calculations. The black curve is a guide to the eye, to show the small but finite component of the wave function that exists outside the Coulomb potential. f, MLESO energy shift with respect to the energy E(B = 0 T) as a function of B, for different values of F_x. The magnitude of the predicted shift is on the same order as in the experimental observation.