Interplay of magnetic and thermodynamic responses in the kagome-triangular system

Abstract: Inspired by the recent experimental progress in pyrochlore derivative \ce{RE3Sb3A2O14 (A=Mg, Zn)}, we investigate the Hubbard model on the kagome lattice with an additional hopping $t'/t$, which enables continuous interpolation between the kagome and triangular lattices by using determinant quantum Monte Carlo simulations. We analyze the evolution of magnetic correlations and thermodynamic responses across different values of $t'/t$ and on-site interaction $U$. It is found that increasing $t'/t$ suppresses short-range antiferromagnetic correlations, while the next-nearest-neighbor correlations exhibit a sign change near $t'/t \approx 0.3 \text{--} 0.4$. Within this regime, the specific heat shows a pronounced low-temperature peak, indicating an emergent spin-related energy scale. Increasing $U$ enhances magnetic correlations and shifts the associated $t'/t$ crossover points to larger values. We also discuss the sign problem to clarify which parameter region of our numerical simulations is accessible and reliable. Our results uncover the competition between frustration and correlations and the interplay of magnetic and thermodynamic responses in the kagome lattice, providing insights into correlated states in frustrated materials.