Trimerized Spin-$1/2$ Chain: Emergent Low-Energy Hamiltonian, Higher-Energy Excitations, and Magnetic and Thermodynamic Responses

Snehasish Sen, Sudhansu S. Mandal

We investigate a spin-1/2 antiferromagnetic chain with trimerized exchange couplings relevant to Na${}_2$Cu${}_3$Ge${}_4$O${}_{12}$. We show that the low-energy Hilbert space maps onto an…