Orbital-dependent singlet state observed in quantum antiferromagnet chain BaCoTe₂O₇

Area of Science:

• Condensed Matter Physics
• Quantum Magnetism

Background:

• Recent theories highlight orbital effects in magnetic systems.
• Spin-3/2 systems present complex magnetic behaviors.

Purpose of the Study:

• Propose an orbital-dependent singlet state for spin-3/2 systems in BaCoTe2O7.
• Investigate magnetic transitions and the origin of the spin gap in this material.

Main Methods:

• Single crystal growth of BaCoTe2O7.
• Magnetic susceptibility, specific heat, and magnetization measurements.
• First-principles density functional theory (DFT) calculations.

Main Results:

• Antiferromagnetic ordering observed at approximately 6 K.
• Phase transition from singlet to triplet ground state identified via magnetization.
• Block magnetic structure reproduced by DFT calculations.
• Spin gap likely originates from a Heitler-London state.

Conclusions:

• BaCoTe2O7 exhibits antiferromagnetic ordering and a field-induced singlet-triplet transition.
• The material is a potential candidate for observing orbital-selective phases due to large U.
• The spin gap is possibly linked to the formation of a Heitler-London state.