Field-Driven Quantum Criticality in the Spinel Magnet ZnCr_{2}Se_{4}

Area of Science:

• Condensed Matter Physics
• Quantum Magnetism

Background:

• Frustrated magnets like ZnCr2Se4 exhibit complex magnetic behaviors due to competing interactions.
• Understanding spin state transitions under external magnetic fields is crucial for exploring quantum phenomena.

Purpose of the Study:

• To investigate the magnetic properties and quantum phase transitions of the frustrated magnet ZnCr2Se4.
• To characterize the low-energy excitations and quantum criticality in this 3D material.

Main Methods:

• Detailed measurements of dc and ac magnetic susceptibilities.
• Specific heat and thermal conductivity experiments were conducted.
• Phase diagram mapping under varying magnetic fields.

Main Results:

• Observed spin state transitions from helix to spiral to fully polarized states with increasing magnetic field.
• Identified a direct quantum phase transition from the spiral to the fully polarized state.
• Detected unconventional T^2-dependent specific heat and temperature-independent mean free path, indicating strong quantum fluctuations.

Conclusions:

• ZnCr2Se4 displays field-driven quantum criticality, a rare phenomenon in 3D magnets.
• The findings suggest frustrated quantum criticality with extended critical modes.
• The study highlights unconventional properties near the quantum critical point.