Recently, the team led by Associate Professor Li Linhu from the School of Physics and Astronomy at Sun Yat-sen University, supported by the National Natural Science Foundation of China's Young Scientists Fund and the Youth Project of the Major Talent Engineering of Guangdong Province, discovered a new phenomenon of occupation-dependent particle separation in the study of many-body non-Hermitian systems. The findings were published in Physical Review Letters.
The lead author of the paper, Qin Yi, a postdoctoral researcher at the School of Physics and Astronomy at Sun Yat-sen University, stated that many-body interactions can induce a variety of phenomena beyond the single-particle picture, which is one of the significant frontier topics in condensed matter and quantum physics. When coupled with the external environment, quantum many-body systems can be effectively described by non-Hermitian Hamiltonians. These Hamiltonians exhibit many properties distinctly different from Hermitian systems, attracting considerable attention from theoretical and experimental researchers in recent years.
Among these, the non-Hermitian skin effect, a major focus in non-Hermitian physics research, is primarily characterized by the massive accumulation of single-particle eigenstates at the system's boundaries, leading to unique physical phenomena such as non-reciprocal unidirectional transport and quantized steady-state response.
The researchers discovered an “occupation-dependent particle separation” phenomenon in a many-body non-Hermitian system, using hard-core bosons as an example, resulting from the synergistic production of the many-body statistical properties and the non-Hermitian skin effect. This phenomenon arises from the skin-effect reversal property in a class of single-particle models, i.e., when multiple non-Hermitian skin channels in the same direction exist in the system, their destructive coherence leads to an overall non-Hermitian skin effect in the opposite direction.
In the hard-core boson system, its hard-core nature restricts the coherence between different non-Hermitian skin channels, causing paired particles occupying the same cell to exhibit a non-Hermitian skin effect opposite to that of unpaired particles. This occupation-dependent non-Hermitian skin effect was further verified through calculations of local sub-lattice correlations and entanglement entropy. Dynamically, this phenomenon manifests as unidirectional or bidirectional transport for different many-body initial states, thereby providing a new mechanism for spatially separating paired and unpaired particles.
Li Linhu, the corresponding author of the paper, stated that this discovery reveals the significant impact of particle non-conservation and spatial configurations in subsystems (such as orbits, sub-lattices, or spins) on non-Hermitian physical properties, offering new insights for designing and exploring novel many-body non-Hermitian phenomena.
Relevant paper information: https://doi.org/10.1103/PhysRevLett.132.096501
