Quantum-Squeezing-Induced Point-Gap Topology and Skin Effect.

Area of Science:

• Condensed Matter Physics
• Quantum Physics
• Topological Materials

Background:

• Topological phases of matter, such as quantum spin-Hall insulators, are typically characterized by bulk invariants and edge states.
• Non-Bloch topological physics extends topological concepts beyond the standard Bloch theorem, revealing phenomena like the skin effect where eigenstates localize.
• Quantum squeezing, a non-classical state of light or other quantum systems, has been explored for enhanced precision measurements.

Purpose of the Study:

• To theoretically predict and characterize a novel topological phase in a one-dimensional (1D) quadratic-bosonic system.
• To investigate the interplay between quantum squeezing and topology, leading to a symmetry-protected Z_{2} skin effect.
• To identify experimental signatures for observing this topological phase and its associated skin effect.

Main Methods:

• Theoretical prediction using a one-dimensional quadratic-bosonic Hamiltonian.
• Analysis of time-reversal symmetry and the introduction of a novel Z_{2} invariant.
• Investigation of the phase diagram to identify the parameter regime for the Z_{2} skin effect.
• Focus on zero energy states and the concept of real- and point-gap coexisting topological phases.

Main Results:

• Prediction of a squeezing-induced point-gap topology.
• Identification of a symmetry-protected Z_{2} skin effect, characterized by a novel Z_{2} invariant.
• The Z_{2} skin effect occurs in a phase characterized by coexisting real and point gaps.
• The predicted phenomena are experimentally observable through the steady-state power spectral density.

Conclusions:

• The study introduces quantum squeezing as a tool to enrich non-Bloch topological physics.
• A novel Z_{2} skin effect, protected by time-reversal symmetry, is theoretically demonstrated.
• The findings suggest potential applications in engineering symmetry-protected sensors based on the Z_{2} skin effect.