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Basic Electronic Structures and Charge Carrier Generation in Organic Optoelectronic Materials
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
When an energy-matched photon hits a semiconductor, an exciton is usually first formed as shown in Figure 3.24. An exciton is a bound state of an electron and an imaginary particle called hole (a vacant site of an electron with one positive charge) and thus is also called a correlated electron–hole pair. Correlated means free electron spins are not detectable via the electron spin resonance (ESR) or electron paramagnetic resonance (EPR) even if the excited single electron is at the LUMO orbital, and one remaining single electron is at HOMO orbital after the excitation. Exciton is a quasi particle. A quasiparticle refers to a particle-like entity arising in certain systems of interacting particles. It can be thought of as a single particle moving through the system, surrounded by a cloud of other particles that are being pushed out of the way or dragged along by its motion, so that the entire entity moves along somewhat like a free particle. Excitons are integer spin particles, thus obeying Bose statistics in the low-density limit. An exciton can diffuse in the material from one site to another called exciton diffusion or more frequently called energy transfer process (to be described in detail later). Excitons can be treated in two limiting cases that depend on the properties of the material in question.
Quantum Dynamics of Tribosystems
Published in Dmitry N. Lyubimov, Kirill N. Dolgopolov, L.S. Pinchuk, Quantum Effects in Tribology, 2017
Dmitry N. Lyubimov, Kirill N. Dolgopolov, L.S. Pinchuk
Quasiparticle is a fundamental concept in quantum theory, the introduction of which radically simplifies the physical picture of the world and the methods to describe a wide range of processes in systems of many particles with strong interaction. A quasiparticle is a special long-living multiparticular complex, which, unlike ordinary particles that form a system, weakly interacts with its environment. Therefore, a quasiparticle is in a special quantum state with its own wave function, energy, momentum, spin, etc. A quasiparticle, being a collective formation, is continuously renewing in motion composition that remains fixed only in extreme cases [73].
Alternative theories of cuprate superconductivity
Published in J. R. Waldram, Superconductivity of Metals and Cuprates, 2017
It has also been suggested that the cuprates might be similar to the heavy-fermion superconductors, in which, as we saw in Section 11.9, there is a large renormalization of the mass due to interactions between the s–d–f electrons and decaying magnetic fluctuations associated particularly with the same band. In both types of material there is evidence that the form of the residual interaction between the quasiparticles favours non-s-wave superconductivity. Until theories have been worked out in more detail for both cuprates and heavy fermions it remains unclear whether we are dealing with closely parallel mechanisms.
Variational approaches to quantum impurities: from the Fröhlich polaron to the angulon
Published in Molecular Physics, 2019
Xiang Li, Giacomo Bighin, Enderalp Yakaboylu, Mikhail Lemeshko
The concept of quasiparticle is one of the most fertile and far-reaching concepts in condensed-matter physics. When thinking in terms of quasiparticles one aims to describe collective excitations of a many-body system as effective emergent particles, hence the name [1].