Valence-Bond-Glass State with Singlet Gap in the Spin-1/2 Square-Lattice Random $J_1$-$J_2$ Heisenberg Antiferromagnet Sr$_2$CuTe$_{1-x}$W$_x$O$_6$

Masari Watanabe; Nobuyuki Kurita; Hidekazu Tanaka; Wataru Ueno; Kazuki Matsui; Takayuki Goto

doi:10.1103/PhysRevB.98.054422

paper

Valence-Bond-Glass State with Singlet Gap in the Spin-1/2 Square-Lattice Random $J_{1}$ - $J_{2}$ Heisenberg Antiferromagnet Sr $_{2}$ CuTe $_{1 - x}$ W $_{x}$ O $_{6}$

arXiv:1808.02614 · doi:10.1103/PhysRevB.98.054422

Abstract

The double-perovskite compounds Sr $_{2}$ CuTeO $_{6}$ and Sr $_{2}$ CuWO $_{6}$ are magnetically described as quasi-two-dimensional spin-1/2 square-lattice $J_{1} - J_{2}$ Heisenberg antiferromagnets with predominant $J_{1}$ and $J_{2}$ exchange interactions, respectively. We report the low-temperature magnetic properties of Sr $_{2}$ CuTe $_{1 - x}$ W $_{x}$ O $_{6}$ with randomness in the magnitudes of $J_{1}$ and $J_{2}$ . It was found that the low-temperature specific heat for $0.1 \leq x \leq 0.5$ has a large component proportional to the temperature $T$ above 1.2 K, although the low-temperature specific heat for the two parent systems is approximately proportional to $T^{3}$ . With decreasing temperature below 1.2 K, the $T$ -linear component decreases rapidly toward zero, which is insensitive to the magnetic field up to 9 T. This is suggestive of the singlet excitation decoupled from the magnetic field. The NMR spectrum for $x = 0.2$ exhibits no long-range order down to 1.8 K. These results indicates that the ground state of Sr $_{2}$ CuTe $_{1 - x}$ W $_{x}$ O $_{6}$ is a valence-bond-glass state with singlet gaps.

6 pages, 5 figures

Valence-Bond-Glass State with Singlet Gap in the Spin-1/2 Square-Lattice Random J1​-J2​ Heisenberg Antiferromagnet Sr2​CuTe1−x​Wx​O6​

Abstract

Valence-Bond-Glass State with Singlet Gap in the Spin-1/2 Square-Lattice Random $J_{1}$ - $J_{2}$ Heisenberg Antiferromagnet Sr $_{2}$ CuTe $_{1 - x}$ W $_{x}$ O $_{6}$