Thermal and dynamical properties of the S=1/2 bilayer breathing-kagome Heisenberg magnet - application to Ca₁₀Cr₇O₂₈ -

Recent experimental studies suggested that Ca₁₀Cr₇O₂₈ [1] is a promising candidate for a quantum spin liquid (QSL) ground state. Several theoretical studies applied to the proposed Hamiltonian and captured many features of experiments; however, they involved some level of approximation and left open the role of quantum effects at finite temperature.

We investigated the thermal and dynamical properties of the proposed Hamiltonian, S=1/2 bilayer breathing-kagome Heisenberg model, using the non-biased exact diagonalization (ED) and thermal pure quantum state (TPQ) methods. Especially, our sophisticated ED code enabled us to treat a much larger system up to about 2000 spins at high field. We succeeded in reproducing both ring and pinch point structures, which were observed in the inelastic neutron scattering measurements as the characteristic features of the QSL state, in the calculated dynamical spin structure factors without any approximation to our Hamiltonian. Our TPQ calculations could also show good agreement with the experimental thermodynamic results in specific heat and magnetization curves[2].

[1] C. Balz, et al, Nat. Phys. 12, 942 (2016). [2] T. Shimokawa, R. Pohle, H. Yan and N. Shannon, in preparation.