Tellurium-bridged two-leg spin ladder inBa2CuTeO6

Abstract

We present single-crystal growth and magnetic property studies of telluriumbridged copper spin-1/2 system Ba2CuTeO6. The spin-exchange interaction among copper spins via Cu-O-Te-O-Cu super-superexchange route leads to a novel two-leg spin ladder system. Spin susceptibility χ(T) data indicates that the triclinic Ba2CuTeO6 undergoes a stepwise crossover for exchange couplings revealed by a broad maximum near Tmax~75 K and an anisotropic cusp in ddT(T) at TN~15 K to signify a three dimensional (3D) antiferromagnetic long-range ordering (LRO). The 3D LRO has been suggested from the anisotropic behavior of (T) with strong c-axis spin anisotropy and the signature of spin flop transition from the isothermal magnetization below TN. Analysis of magnetic heat capacity (Cm) at TN~15 K indicates that most of the spin entropy (~92 % ) has already been released above TN, which supports the picture of consecutive spin entropy reduction upon cooling with Te-bridged two-leg spin ladder system with strong intraladder and interladder couplings. Theoretical DFT+U calculations have been performed to search for the ground state magnetic configuration and also to evaluate exchange coupling constants that support the magnetic model deduced from the combined spin susceptibility and crystal structure symmetry analysis. 2 1 0

Quantum criticality in the coupled two-leg spin ladder Ba2CuTeO6

“…Our data are in a good accordance with the previously reported results 23,24 . With decreasing temperature, χ(T ) first displays a broad maximum at about 75 K with the subsequent drop and then a small kink at about T N ∼ 15 K. The 75 K broad maximum is a common feature of low-dimensional antiferromagnets developing short-range spin correlations.…”

“…The S = 1/2 Cu 2+ ions are coupled through complex Cu-O-Te-O-Cu superexchange paths, giving rise to six main exchange interactions J i (i = 1 − 6). Depending on the relative strength of J 2 and J 3 , two different ladder models have been proposed: (i) a two-leg spin ladder with J 1 = J l and J 3 = J r 23 and (ii) a two-leg spin ladder with J 1 = J l and J 2 = J r within the bc plane 24 . The residual in-and inter-plane interladder couplings stabilize a possible low-temperature magnetic ordering.…”

“…At low temperatures, the RVB state is preempted by the development of long-range magnetic ordering at T N = 15−16 K, indicated by a small kink in the magnetic susceptibility 23,24 . However, the magnetic transition is largely hidden, while showing no magnetic Bragg peaks, no divergence of 1/T 1 , and no apparent λ-like anomaly in the specific heat.…”

S=12quantum critical spin ladders produced by orbital ordering inBa2CuTeO6

“…After submission of our manuscript another paper reporting the physical properties of Ba 2 CuTeO 6 was published by Rao et al [31]. Rao et al identify the same features as we do in susceptibility, also see the weak transition at H ≈ 1.5T in M(H ) and also fail to detect a sharp anomaly in zero field specific heat although they do see an extremely weak hump in the vicinity of T mag .…”

Tensor network state approach to quantum topological phase transitions and their criticalities of Z2 topologically ordered states

“…With such tensor network states, many properties of the topological phases, such as entanglement entropy, entanglement spectrum 9 , modular matrices 10 and all kinds of expectation values, can be efficiently calculated numerically. In one dimension, from the exact ground-state wave functions in the matrix product state representation, we have successfully decoded the quantum criticalities of the topological phase transitions from the symmetry protected topological (SPT) phases to their adjacent trivial phase with the same symmetry [11][12][13][14] .…”