PGI-1 Talk: Sayan Banik

Quantum Theory of Materials Seminar

Skyrmion-Antiskyrmion Lattice: Coexistence of Topological Particle and Its Antiparticle

We report the finding of a thermodynamically stable skyrmion-antiskyrmion lattice (S-AL) in two-dimensional chiral magnets, a paradoxical phenomenon where skyrmions (Q = −1) and antiskyrmions (Q = 1) form a regular long-range ordered lattice despite their inherent propensity for mutual annihilation, akin to particle-antiparticle interactions. This net-zero global topological charge state, resulting from balanced populations of oppositely charged solitons, is demonstrated as a magnetic field-induced topological ground state in frustrated chiral magnets with competing anisotropic interactions—specifically Dzyaloshinskii-Moriya and frustrated exchange interactions—where reduced symmetry (C1v) plays a critical role.

We develop a micromagnetic model that describes the emergence of S-AL as a thermodynamically stable ground state. Using density functional theory and atomistic spin-lattice simulations, we identify three interfacial magnetic films— 2Fe/InSb(110), 2Fe/GaAs(110), and 2Fe/CdTe(110)—as ideal candidates. In these C1v-symmetric heterostructures, exchange frustration and symmetry-enforced anisotropic interactions stabilize the net-zero lattice against annihilation. We reveal a magnetic field-driven ground state phase sequence: cycloidal spin-spiral → S-AL → conical spin-spiral  → ferromagnet.

This finding establishes anisotropic frustrated chiral magnets as a material class enabling stable net-zero topological soliton lattices within a single magnetic layer, resolving the paradox of coexisting oppositely charged entities as the ground state.

Contact

Prof. Dr. Stefan Blügel
Phone: +49 2461 61-4249
Email: s.bluegel@fz-juelich.de

Sayan Banik
NISER India
Email: sayan.banik@niser.ac.in