Geometric contribution to adiabatic amplification in non-Hermitian systems

Abstract

Concepts from non-Hermitian quantum mechanics have proven useful in understanding and manipulating a variety of classical systems, such as those encountered in optics, classical mechanics, and metamaterial design. Recently, the non-Hermitian analog of the Berry phase for adiabatic processes was experimentally measured. In non-Hermitian systems, the Berry phase can have an imaginary part, which contributes to the amplification or decay of the total wave intensity. When the imaginary part of the Berry curvature is zero, this geometric amplification factor is determined solely by the initial and final points of the adiabatic path in parameter space, and it does not depend on how these points are connected by the path. We list classes of non-Hermitian Hamiltonians where this path independence is guaranteed by suitable symmetries, and we find that, for some of these classes, the amplification factor can be written only in terms of the Petermann factors of the initial and final points. Our result can, in turn, be used to experimentally obtain the Petermann factor by observing how the norm of the wave function changes under adiabatic processes. We validate our theory using a couple of concrete examples of physical relevance.

15 pages, 4 figures

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Cited by in corpus (6)

• Generalized Petermann factor of non-Hermitian systems at exceptional points
• Quantum geometrical effects in non-Hermitian systems
• Exceptionally deficient topological square-root insulators
• Topological photonics in nanoscaled systems with far field radiation and polarization singularities
• Minimal Hamiltonian deformations as bulk probes of effective non-Hermiticity in Dirac materials
• Covariant formulation of the Berry connection in non-Hermitian systems