Origin of spin-gap in CaV${}_4$O${}_9$: effect of frustration and lattice distortion

O. A. Starykh, M. E. Zhitomirsky, D. I. Khomskii +2

We study the origin of spin-gap in recently discovered material CaV${}_4$O${}_9$. We analyze the spin-$1/2$ Heisenberg model on the $1/5$ depleted square lattice with nearest neighbor…