Probing quantum phase transition point by tuning an external anti trap

Area of Science:

• Atomic, Molecular, and Optical Physics
• Condensed Matter Physics
• Quantum Simulation

Background:

• Ultracold atoms in optical lattices are key for studying condensed-matter models like the Hubbard model.
• Bosonic atoms exhibit phase transitions between superfluid and Mott insulator states.
• Inhomogeneity in conventional optical lattices broadens phase transitions, obscuring critical points.

Purpose of the Study:

• To develop a method for precisely probing phase transition points in inhomogeneous cold atom systems.
• To overcome the limitations of broad phase transitions caused by Gaussian optical lattice geometry.

Main Methods:

• Utilized ultracold bosonic atoms in an optical lattice.
• Applied a blue-detuned laser to counteract the Gaussian inhomogeneity of the optical lattice.
• Monitored changes in visibility to identify phase transition indicators.

Main Results:

• Identified a distinct jump point in visibility corresponding to a specific trap depth.
• This jump signifies the precise onset of the Mott insulator phase in an inhomogeneous system.
• Demonstrated a simple and effective method for detecting quantum phase transitions.

Conclusions:

• The applied blue-detuned laser successfully compensates for lattice inhomogeneity, enabling precise phase transition detection.
• This technique provides a simple method to pinpoint the critical point for superfluid to Mott insulator transitions.
• The method is expected to be a valuable tool for various cold atom experiments studying phase transitions.