Proximate deconfined quantum critical point in SrCu₂(BO₃)₂.

Area of Science:

• Condensed matter physics
• Quantum magnetism
• Quantum phase transitions

Background:

• The deconfined quantum critical point (DQCP) is a theoretical framework describing exotic order-order transitions in quantum matter.
• Experimental realization of DQCPs has been challenging, limiting the study of their unique properties.

Purpose of the Study:

• To experimentally investigate the existence and properties of a DQCP in the quantum magnet SrCu2(BO3)2.
• To explore magnetic field-induced transitions under high pressure.

Main Methods:

• High-pressure 11B nuclear magnetic resonance (NMR) measurements were performed on SrCu2(BO3)2.
• Magnetic field-induced phase transitions were studied at low temperatures (0.07 K) and high pressures (up to 2.4 GPa).

Main Results:

• A magnetic field-induced transition from a plaquette singlet state to an antiferromagnetic state was observed above 1.8 GPa.
• First-order transition signatures diminished with increasing pressure.
• Quantum critical scaling and emergent O(3) symmetry were observed at 2.4 GPa, consistent with a proximate DQCP.

Conclusions:

• The study provides strong experimental evidence for a DQCP in SrCu2(BO3)2.
• The findings suggest that critical quantum fluctuations and emergent O(3) symmetry are key features of this system.
• SrCu2(BO3)2 serves as a promising experimental platform for future DQCP research.