A microscopic (Hamiltonian-based) method for the quantum statistics of bosonic excitations in a two-mode magnon system is developed. Both the exchange and the dipole-dipole interactions, as well as the Zeeman term for an external applied field, are included in the spin Hamiltonian, and the model also contains the nonlinear effects due to parallel pumping and four-magnon interactions. The quantization of spin operators is achieved through the Holstein-Primakoff formalism, and then a coherent magnon state representation is used to study the occupation magnon number and the quantum statistical behaviour of the system. Particular attention is given to the cross correlation between the two coupled magnon modes in a ferromagnetic nanowire geometry formed by two lines of spins. Manipulation of the collapse-and-revival phenomena for the temporal evolution of the magnon number as well as the control of the cross correlation between the two magnon modes is demonstrated by tuning the parallel pumping field amplitude. The role of the four-magnon interactions is particularly interesting and leads to anti-correlation in some cases with coherent states.
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http://dx.doi.org/10.1088/1361-648X/aa67a3 | DOI Listing |
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January 2025
Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, China.
A novel polymer electrolyte based on CsPbI quantum dots (QDs) reinforced polyacrylonitrile (PAN), named as PIL, is exploited to address the low room-temperature (RT) ion conductivity and poor interfacial compatibility of polymer solid-state electrolytes. After optimizing the content of CsPbI QDs, RT ion conductivity of PIL largely increased from 0.077 to 0.
View Article and Find Full Text PDFBackground: The full pentavalent (DPT-HepB-Hib) vaccination is the main strategy to prevent five communicable diseases in early childhood, especially in countries with huge communicable disease burdens like Ethiopia. Exploring spatial distributions and determinants of full pentavalent vaccination status in minor ecological areas in Ethiopia is crucial for creating targeted immunization campaigns and monitoring the advancement of accomplishing sustainable development goals. This study aimed to investigate the spatial disparities and determinants of full pentavalent vaccination among 12-23-month-old children in Ethiopia.
View Article and Find Full Text PDFNature
January 2025
Department of Physics and Astronomy, Rice University, Houston, TX, USA.
It is commonly believed that there are only two types of particle exchange statistics in quantum mechanics, fermions and bosons, with the exception of anyons in two dimensions. In principle, a second exception known as parastatistics, which extends outside two dimensions, has been considered but was believed to be physically equivalent to fermions and bosons. Here we show that non-trivial parastatistics inequivalent to either fermions or bosons can exist in physical systems.
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January 2025
Department of Physics, Brown University, Providence, RI, USA.
Excitons, Coulomb-driven bound states of electrons and holes, are typically composed of integer charges. However, in bilayer systems influenced by charge fractionalization, a more interesting form of interlayer exciton can emerge, in which pairing occurs between constituents that carry fractional charges. Despite numerous theoretical predictions for these fractional excitons, their experimental observation has remained unexplored.
View Article and Find Full Text PDFNature
January 2025
Department of Physics, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China.
The concept of non-Hermiticity has expanded the understanding of band topology, leading to the emergence of counter-intuitive phenomena. An example is the non-Hermitian skin effect (NHSE), which involves the concentration of eigenstates at the boundary. However, despite the potential insights that can be gained from high-dimensional non-Hermitian quantum systems in areas such as curved space, high-order topological phases and black holes, the realization of this effect in high dimensions remains unexplored.
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