Effect of Quantum Fluctuations on Magnetic Ordering in CaV$_3$O$_7$

TL;DR

This paper investigates how quantum fluctuations influence magnetic ordering in CaV$_3$O$_7$, revealing that quantum effects stabilize a stripe phase not predicted by classical theory, with specific coupling ratios estimated from experiments.

Contribution

The study introduces a modified spin wave theory to demonstrate quantum stabilization of the stripe phase in a $1/4$-depleted square spin-$1/2$ Heisenberg model, aligning with experimental data.

Findings

Quantum fluctuations stabilize the stripe phase for $J'/J > 0.69$.

Classical theory does not predict the observed magnetic order.

Estimated coupling constants are approximately equal ($J oughly J'$).

Abstract

We present a theoretical model for CaV$_3$O$_7$: the $1/4$-depleted square spin-$1/2$ Heisenberg model which includes both the nearest-neighbor coupling ($J$) and the next-nearest-neighbor coupling ($J'$), where $J$ and $J'$ are antiferromagnetic. Recent experiments of the neutron diffraction by Harashina et.al. report the magnetic ordering at low temperatures, which may be called as a stripe phase. It is shown that the observed spin structure is not stable in the classical theory. By employing the modified spin wave theory, we show that the stripe phase is stabilized by the quantum fluctuations for $J'/J > 0.69$. In CaV$_3$O$_7$, the coupling constants are estimated as $J \sim J'$ by comparing the theoretical and experimental results.