LAUSR

Asymmetric destruction of the one-third magnetization plateau upon heating is found in the spin-$\frac{1}{2}$ kagome Heisenberg antiferromagnets by using the typical pure quantum state approach. The asymmetry originates from a density of states of low-lying excited states of ${N}_{\mathrm{s}}$ spin systems with magnetization $(1/3\ensuremath{-}2/{N}_{\mathrm{s}})$ that is larger than the density of states of low-lying states with magnetization $(1/3+2/{N}_{\mathrm{s}})$. 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 how the asymmetry originates from the unprecedented preservation of the ice rule around the plateau.