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TT: Fachverband Tiefe Temperaturen

TT 29: Frustrated Magnets: General

TT 29.14: Talk

Wednesday, March 29, 2023, 13:00–13:15, HSZ 201

Exact analytical solutions of a distorted spin-1/2 tetrahedron with ring exchange — Rolf Schumann¹ and •Stefan-Ludwig Drechsler² — ¹TU-Dresden, D-1169 Dresden, Germany — ²IFW-Dresden, D-1169 Dresden, Germany

We present exact analytical solutions for the eigenvalues of a general spin-1/2 Hamiltonian with 6 bilinear (Heisenberg) J_i and 3 ring exchange K_i couplings. Focusing on the experimentally interesting orthorhombically, tetragonally, trigonally and non-distorted ideal tetrahedra (ITH) we consider their thermodynamic properties as the magnetization M, susceptibility, entropy, and specific heat at any temperature T and external magnetic field H and derive from the magnetization steps M(H) at high-fields and low-T the saturation field H_s, the critical ferrimagnetic field H_c1, and the width of the corresponding plateau as a function of the cyclicity . As a result we find enhanced H_s and lowered H_c1 values with increasing ring exchange K>0 due to the reduced frustration. We present exact mapping equations to extract the relevant exchange integrals J_i and K_i from experimentally observed transition energies and provide an analytical mapping of the single-band Hubbard model on the ITH valid at any coupling strength U/t, where U is the onsite Coulomb repulsion and t the NN-hopping integral. The experimental situations with respect to the magnitude and sign of κ=J/K for Cu₂Te₂OBr₂, Cu₂OSeO₃, and Cu₄X₆L₄ with X=Cl,Br and L being various ligands are briefly discussed.