Asymmetric melting of one-third plateau in kagome quantum antiferromagnets

Asymmetric destruction of the one-third magnetization plateau upon heating is found in the spin-1/2 kagome Heisenberg antiferromagnets using the typical pure quantum state approach. The asymmetry originates from larger density of states of low-lying excited sates of $N_{\mathrm{s}}$ spin systems with magnetization $(1\mathrm{/}3-2\mathrm{/}{N}_{\mathrm{s}})$ than that of low-lying sates with magnetization $(1\mathrm{/}3+2\mathrm{/}{N}_{\mathrm{s}})$. The enhanced specific heat and entropy that reflect the larger density of states in the lower-field side of the plateau are detectable in candidate materials of the kagome antiferromagnets. We discuss that the asymmetry originates from the unprecedented preservation of the ice rule around the plateau.