S=1/2 quantum critical spin ladders produced by orbital ordering in Ba2CuTeO6

TL;DR

Ba2CuTeO6 exhibits weakly coupled S=1/2 spin ladders with signs of quantum criticality, showing magnetic anomalies and strong quantum fluctuations near a transition point, despite lacking long-range order.

Contribution

This study identifies Ba2CuTeO6 as a realization of quantum critical spin ladders influenced by orbital ordering, highlighting its proximity to a quantum critical point.

Findings

Magnetic susceptibility fits isolated spin ladder model with J~86 K.

Anomaly at T_mag=16 K suggests magnetic transition.

No long-range order detected in NMR, specific heat, or neutron diffraction.

Abstract

The ordered hexagonal perovskite Ba2CuTeO6 hosts weakly coupled S=1/2 spin ladders produced by an orbital ordering of Cu2+. The magnetic susceptibility chi(T) of Ba2CuTeO6 is well described by that expected for isolated spin ladders with exchange coupling of J~86 K but shows a deviation from the expected thermally activated behavior at low temperatures below T*~25 K. An anomaly in chi(T), indicative of magnetic ordering, is observed at T_mag=16 K. No clear signature of long-range ordering, however, is captured in NMR, specific heat or neutron diffraction measurements at and below T_mag. The marginal magnetic transition, indicative of strong quantum fluctuations, is evidence that Ba2CuTeO6 is in very close proximity to a quantum critical point between a magnetically ordered phase and a gapped spin liquid controlled by inter-ladder couplings.