Physica Pub Date : 1974-10-15 DOI: 10.1016/0031-8914(74)90267-5

J. Ward, J. Cooper, E.W. Smith

引用次数: 0

Excitation spectrum and electromagnetic properties of the electron-exciton bound states in molecular crystals 分子晶体中电子-激子束缚态的激发谱和电磁特性

Physica Pub Date : 1974-10-15 DOI: 10.1016/0031-8914(74)90265-1

C. Mavroyannis

{"title":"Excitation spectrum and electromagnetic properties of the electron-exciton bound states in molecular crystals","authors":"C. Mavroyannis","doi":"10.1016/0031-8914(74)90265-1","DOIUrl":"10.1016/0031-8914(74)90265-1","url":null,"abstract":"<div>A self-consistent approach is used to study the excitation spectrum due to the coherent electron-exciton pairing for a two-level system of a molecular crystal. It is shown that the interaction between an excited electron and a Frenkel exciton, which are located at adjacent lattice sites in the crystal, leads to the formation of a bound state provided that certain conditions are satisfied. The excitation spectrum is found to be of the superconductivity type and the electron-exciton quasiparticle moves through the crystal with definite energy and wavevector. The gap function due to the electron-exciton pairing is calculated at zero temperature and an expression for the ground-state energy is derived. Then the electromagnetic properties of the electron-exciton bound states are discussed. An expression for the dielectric function is obtained describing the interaction between the transverse photons and the two charged quasiparticles which arise from the electron-exciton pairing. In the presence of electron-exciton pairing, the paramagnetic current consists of two terms arising from the two frequency modes, which in the long-wavelength limit cancel each other to the order of Δ/EνO, where Δ is the gap function due to the electron-exciton pairing and EνO is the energy difference between the excited and ground state. Thus for Δ ⪡ EνO the diamagnetic current in the long-wavelength limit is the same as in London's theory indicating the existence of the Meissner effect. In the absence of pairing the diamagnetic current vanishes.</div>","PeriodicalId":55605,"journal":{"name":"Physica","volume":"77 2","pages":"Pages 343-360"},"PeriodicalIF":0.0,"publicationDate":"1974-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0031-8914(74)90265-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75461125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6

Persistent currents in the saturated He-II film, induced by rotation 旋转引起的饱和He II薄膜中的持续电流

Physica Pub Date : 1974-10-01 DOI: 10.1016/0031-8914(74)90281-X

H.J. Verbeek, E. Van Spronsen, H. Van Beelen, R. De Bruyn Ouboter, K.W. Taconis

引用次数: 5

1/f noise in thermo EMF of intrinsic and extrinsic semiconductors 本征和非本征半导体热EMF中的1/f噪声

Physica Pub Date : 1974-10-01 DOI: 10.1016/0031-8914(74)90277-8

Th.G.M. Kleinpenning

引用次数: 66

Anderson-Grüneisen parameter δ and the temperature dependence of the bulk modulus of some fluorides 某些氟化物体积模量的anderson - grisen参数δ和温度依赖性

Physica Pub Date : 1974-10-01 DOI: 10.1016/0031-8914(74)90280-8

R. Ramji Rao

引用次数: 3

Kinetic equation for a high intensity monomode laser 高强度单模激光器的动力学方程

Physica Pub Date : 1974-10-01 DOI: 10.1016/0031-8914(74)90286-9

P. Mandel

引用次数: 0

Energy levels and hyperfine structures in the (5d + 6s)3 configurations of La I La I的(5d + 6s)3构型的能级和超精细结构

Physica Pub Date : 1974-10-01 DOI: 10.1016/0031-8914(74)90283-3

Z. Ben Ahmed, C. Bauche-Arnoult, J.-F. Wyart

引用次数: 16

On the influence of heat transport on low- frequency paramagnetic spin—Lattice relaxation experiments 热输运对低频顺磁自旋-晶格弛豫实验的影响

Physica Pub Date : 1974-10-01 DOI: 10.1016/0031-8914(74)90278-X

J. Flokstra, G.J. Gerritsma, G.A. Hartemink, L.C. Van Der Marel

{"title":"On the influence of heat transport on low- frequency paramagnetic spin—Lattice relaxation experiments","authors":"J. Flokstra, G.J. Gerritsma, G.A. Hartemink, L.C. Van Der Marel","doi":"10.1016/0031-8914(74)90278-X","DOIUrl":"10.1016/0031-8914(74)90278-X","url":null,"abstract":"<div>In low-frequency relaxation experiments on paramagnetic crystals, placed in liquid helium, often dispersion- and absorption curves are found, strongly deviating from those following from the thermodynamic theory of Casimir and Du Pré. For the relaxation time τabs, related to the maximum in the absorption curve, a temperature dependence <math><mtext>τ</mtext><msub><mi></mi><mn>abs</mn></msub><mtext> </mtext><msup><mi></mi><mn>α</mn></msup><mtext>T</mtext><msup><mi></mi><mn>-α</mn></msup></math> with 1 < α < 6 has been found frequently, accompanied sometimes with a jump at the helium-transition temperature Tλ. We computed, starting from a model including the heat conduction of lattice and helium bath and a heat resistance from crystal to bath, dispersion- and absorption curves and found that, assuming the direct process for the spin—lattice relaxation, τabs(T) (related to the maximum of the calculated absorption curve) can be described roughly as mentioned above with a jump at Tγ.</div>","PeriodicalId":55605,"journal":{"name":"Physica","volume":"77 1","pages":"Pages 99-120"},"PeriodicalIF":0.0,"publicationDate":"1974-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0031-8914(74)90278-X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72792586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 14

Nonlinear magnetization of niobium near Hc2 铌在Hc2附近的非线性磁化

Physica Pub Date : 1974-10-01 DOI: 10.1016/0031-8914(74)90275-4

E.A. Burgemeister, Z. Dokoupil

引用次数: 3

Lowest-order optical second-harmonic process in a two-level system 二能级系统中的最低阶光学二次谐波过程

Physica Pub Date : 1974-10-01 DOI: 10.1016/0031-8914(74)90287-0

B.K. Mohanty

引用次数: 1

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