Orbital ferromagnetism in interacting few-electron dots with strong spin-orbit coupling

Abstract

We study the ground state of N weakly interacting electrons (with N ≤ 10) in a two-dimensional parabolic quantum dot with strong Rashba spin-orbit coupling. Using dimensionless parameters for the Coulomb interaction λ ≲ 1 and the Rashba coupling α ≫ 1, the low-energy physics is characterized by an almost flat single-particle dispersion. From an analytical approach for α → ∞ and N = 2, and from numerical exact-diagonalization and Hartree-Fock calculations, we find a transition from a conventional unmagnetized ground state (for λ < λc) to an orbital ferromagnet (for λ > λc), with a large magnetization and a circulating charge current.We show that the critical interaction strength λc = λc(αa; N) vanishes in the limit α → ∞.