Charge density wave with meronlike spin texture induced by a lateral superlattice in a two-dimensional electron gas

Abstract

The combined effect of a lateral square superlattice potential and the Coulomb interaction on the ground state of a two-dimensional electron gas in a perpendicular magnetic field is studied for different rational values of $\Gamma$, the inverse of the number of flux quanta per unit cell of the external potential, at filling factor $\nu =1$ in Landau level $N=0.$ When Landau level mixing and disorder effects are neglected, increasing the strength $W_0$ of the potential induces a transition, at a critical strength $W_0^{\left(c\right)},$ from a uniform and fully spin polarized state to a two-dimensional charge density wave (CDW) with a meronlike spin texture at each maximum and minimum of the CDW. The collective excitations of this vortex-CDW are similar to those of the Skyrme crystal that is expected to be the ground state near filling factor $\nu =1$. In particular, a broken U(1) symmetry in the vortex-CDW results in an extra gapless phase mode that could provide a fast channel for the relaxation of nuclear spins. The average spin polarization changes in a continuous or discontinuous manner as $W_0$ is increased depending on whether $\Gamma \in \left[1/2,1\right]$ or $\Gamma \in \left[0,1/2\right].$ The phase mode and the meronlike spin texture disappear at large value of $W_0,$ leaving as the ground state a partially spin-polarized CDW if $\Gamma \ne 1/2$ or a spin-unpolarized CDW if $\Gamma =1/2.$

11 pages with 9 eps figures

References in corpus (3)

• Engineering artificial graphene in a two-dimensional electron gas
• Making Massless Dirac Fermions from Patterned Two-Dimensional Electron Gases
• Spin Transitions in Graphene Butterflies at an Integer Filling Factor