Abstract
We study collective excitations in a helical electron liquid on a surface of three-dimensional topological insulator. Electron in helical liquid obeys Dirac-like equation for massless particles and direction of its spin is strictly determined by its momentum. Due to this spin-momentum locking, collective excitations in the system manifest themselves as coupled charge- and spin-density waves. We develop quantum field-theoretical description of spin-plasmons in helical liquid and study their properties and internal structure. Value of spin polarization arising in the system with excited spin-plasmons is calculated. We also consider the scattering of spin-plasmons on magnetic and nonmagnetic impurities and external potentials, and show that the scattering occurs mainly into two side lobes. Analogies with Dirac electron gas in graphene are discussed.PACS: 73.20.Mf; 73.22.Lp; 75.25.Dk.
Highlights
Topological insulator is a new class of solids with nontrivial topology, intrinsic to its band structure
Three-dimensional topological insulators are insulating in the bulk, but have gapless surface states with numerous unusual properties
We develop quantum field-theoretical formalism to describe plasmons in graphene and spinplasmons on a surface of 3D topological insulator based on random phase approximation (RPA)
Summary
Topological insulator is a new class of solids with nontrivial topology, intrinsic to its band structure. Collective excitations (plasmons) in helical liquid on the surface of topological insulator was considered in [11]. A starting point for quantum field-theoretical consideration of plasmons on the surface of topological insulator and in graphene is the many-body Hamiltonian of electrons with Coulomb interaction between them: H=
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