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Spin Dynamics in Low Dimensional Magnetic Structures 低维磁性结构中的自旋动力学
Australian Journal of Physics Pub Date : 2000-08-15 DOI: 10.1071/PH00006
R. Stamps
{"title":"Spin Dynamics in Low Dimensional Magnetic Structures","authors":"R. Stamps","doi":"10.1071/PH00006","DOIUrl":"https://doi.org/10.1071/PH00006","url":null,"abstract":"Maxwell’s equations applied to low-dimensional magnetic structures result in a number of interesting features. For example, the magnetic fields generated by two-dimensional arrays of Heisenberg spins can stabilise long range magnetic order and determine critical temperatures. Aspects of this problem are discussed, and considerations for the dynamic response of weakly coupled arrays of fine magnetic particles are presented. Finally, a form of effective medium theory designed to overcome difficulties in treating magnetostatic interactions in magnetic nanostructures is described.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123406710","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: 1
Density matrix renormalisation group method and symmetries of the Hamiltonian 密度矩阵重整化群方法与哈密顿量的对称性
Australian Journal of Physics Pub Date : 2000-08-15 DOI: 10.1071/PH00023
I. McCulloch, M. Gulácsi
{"title":"Density matrix renormalisation group method and symmetries of the Hamiltonian","authors":"I. McCulloch, M. Gulácsi","doi":"10.1071/PH00023","DOIUrl":"https://doi.org/10.1071/PH00023","url":null,"abstract":"Substantial improvements in the computational effort in a density matrix renormalisation program can be made by utilising symmetries of the Hamiltonian. Extra quantum numbers are always desirable to include in the calculation, since it allows the Hilbert space of the superblock to be refined. Since the speed of the calculation is approximately O(n 3 ) in superblock states, the speed increase in targeting a specific total spin state can be considerable. In this paper a new density matrix renormalisation algorithm is presented which conserves the total spin. The general procedure obtained works for any operator, even operators that do not commute with the Hamiltonian.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116880791","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: 38
A Novel Constraint for the Simplified Description of Dispersion Forces 一种简化色散力描述的新约束
Australian Journal of Physics Pub Date : 2000-08-15 DOI: 10.1071/PH00046
J. Dobson, Bradley P. Dinte, Jun Wang, T. Gould
{"title":"A Novel Constraint for the Simplified Description of Dispersion Forces","authors":"J. Dobson, Bradley P. Dinte, Jun Wang, T. Gould","doi":"10.1071/PH00046","DOIUrl":"https://doi.org/10.1071/PH00046","url":null,"abstract":"We propose a novel use of an exact constraint in the construction of simple approximations for response functions of interacting many-electron systems. Within its simplest local version, the resulting theory gives improved approximations for static atomic dipolar polarisabilities without the direct use of wavefunctions or semi-empirical cutoffs. It leads to correct van der Waals energies between distant planar systems, but over-corrects existing cutoff theories for the van der Waals C 6 coefficient for atoms. It is argued that a nonlocal-response version of the constrained theory will do better.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132251738","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: 7
Finite Temperature Correlation Functions of One-dimensional Interacting Electron Systems 一维相互作用电子系统的有限温度相关函数
Australian Journal of Physics Pub Date : 2000-08-15 DOI: 10.1071/PH00024
G. Bowen, M. Gulácsi, A. Rosengren
{"title":"Finite Temperature Correlation Functions of One-dimensional Interacting Electron Systems","authors":"G. Bowen, M. Gulácsi, A. Rosengren","doi":"10.1071/PH00024","DOIUrl":"https://doi.org/10.1071/PH00024","url":null,"abstract":"The well-known bosonisation method of one-dimensional electron systems is extended to finite temperatures. As an example, the correlation functions of the non-interacting case are explicitly calculated. The presentation is pedagogical and is intended to be accessible to graduate students or physicists who are not experts in this field.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122517997","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: 1
Characterising the Metal-Insulator Transition in Two Dimensions 二维金属-绝缘体过渡的表征
Australian Journal of Physics Pub Date : 2000-08-15 DOI: 10.1071/PH00021
D. Neilson, J. Thakur, E. Tosatti
{"title":"Characterising the Metal-Insulator Transition in Two Dimensions","authors":"D. Neilson, J. Thakur, E. Tosatti","doi":"10.1071/PH00021","DOIUrl":"https://doi.org/10.1071/PH00021","url":null,"abstract":"We investigate the metal—insulator transition in 2D electron systems assuming a percolation mechanism connecting through a network of metallic domains. The size of the domains is determined by the level of disorder and the strength of the electron correlations. The domains are linked through quantum tunneling. We determine the dependence of the resistivity on electron density and temperature by calculating the tunnelling transmission through the potential barriers between the domains. The results are in good agreement with recent experimental measurements.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"261 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131419603","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: 2
Influence of Inversion Symmetry on the Metallic Behaviour in a Dilute Two-dimensional Hole System 反演对称性对稀二维空穴体系中金属行为的影响
Australian Journal of Physics Pub Date : 2000-08-15 DOI: 10.1071/PH00019
A. Hamilton, M. Simmons, M. Pepper, D. Ritchie
{"title":"Influence of Inversion Symmetry on the Metallic Behaviour in a Dilute Two-dimensional Hole System","authors":"A. Hamilton, M. Simmons, M. Pepper, D. Ritchie","doi":"10.1071/PH00019","DOIUrl":"https://doi.org/10.1071/PH00019","url":null,"abstract":"In the past five years numerous experimental studies of a wide variety of low disorder two-dimensional (2D) semiconductor systems have revealed an unexpectedly large decrease in the resistance as the temperature is lowered from T ~ 1 K, suggesting the existence of a 2D metal. Although numerous theories have been put forward to explain this metallic-like behaviour (which contradicts the expectations of one parameter scaling theory), its origins, and the question of whether it persists to T = 0, are still subjects of great debate. We present a detailed study of the influence of inversion symmetry on the B = 0 metallic behaviour in a low density GaAs hole gas close to the apparent two-dimensional metal—insulator transition. The strength of the metallic behaviour (determined by the size of the drop in resistance as T→ 0) is found to be almost independent of the electric field across the hole gas, and is predominantly determined by the magnitude of k F l at low temperatures (i.e. by the low temperature resistivity). These results suggest that the shape of the potential well and spin—orbit effects alone cannot account for the existence of metallic behaviour in low density, strongly interacting 2D systems.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115401321","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: 2
Magnetic fields in spaces with VII0 x VIII isometries. 具有VIII x VIII等距的空间磁场。
Australian Journal of Physics Pub Date : 2000-06-15 DOI: 10.1071/PH99097
C. Dariescu, M. Dariescu
{"title":"Magnetic fields in spaces with VII0 x VIII isometries.","authors":"C. Dariescu, M. Dariescu","doi":"10.1071/PH99097","DOIUrl":"https://doi.org/10.1071/PH99097","url":null,"abstract":"The aim of the present paper is to investigate some globally pathological features of a class of static planary symmetric exact solutions with a G6-group of motion, namely with g44 =i sinh 2 (fiz), by means of the null oblique geodesics and Penrose diagram. Finally, we derive general expressions for the A„(x;y;z)„=1;3 components of the vector potential, satisfying the source-free Maxwell equations and the Lorentz condition, pointing out the in∞uence of the global pathological properties on the behaviour of magnetostatic flelds in such universes. 1. The Geometry of the Model The properties of globally pathological manifolds and the behaviour of difierent matter sources in such universes have always been of real interest because of their implications for a better understanding of gravity and spacetime (Brans and Dicke 1961; Hoyle and Narlikar 1964; Guth 1981; Linde 1982; Collins et al. 1989). In addition to naked singularities, cosmic strings, Bianchi spacetimes, dynamical isotropisation, hollow cylinders and topological domain walls (Vilenkin and Shellard","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133320180","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: 2
The Bose{Einstein Condensation of Anyons 任意子的玻色-爱因斯坦凝聚
Australian Journal of Physics Pub Date : 2000-06-15 DOI: 10.1071/PH99062
Yong Liu
{"title":"The Bose{Einstein Condensation of Anyons","authors":"Yong Liu","doi":"10.1071/PH99062","DOIUrl":"https://doi.org/10.1071/PH99062","url":null,"abstract":"The probability for the Bose{Einstein condensation of anyons is discussed. It is found that the ideal anyon gas near Bose statistics can display BEC behaviour. In addition, the transition point and the speciflc heat are determined.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122735014","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: 0
Preparation of superpositions of SU(2) coherent states of the motion of a trapped ion. 捕获离子运动的SU(2)相干态叠加的制备。
Australian Journal of Physics Pub Date : 2000-06-15 DOI: 10.1071/PH99064
Shi-Biao Zheng
{"title":"Preparation of superpositions of SU(2) coherent states of the motion of a trapped ion.","authors":"Shi-Biao Zheng","doi":"10.1071/PH99064","DOIUrl":"https://doi.org/10.1071/PH99064","url":null,"abstract":"A scheme is presented for the generation of superpositions of two two-mode SU(2) coherent states of the motion for a trapped ion. In the scheme an ion is trapped in a two-dimensional isotropic harmonic potential and driven by two resonant laser beams. Under certain conditions, the motional two-mode SU(2) cat state can be generated after a conditional measurement on the internal state following the ion-laser interaction.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114853253","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
Scheme for direct measurement of the two-mode Wigner function in cavity QED and ion traps. 在腔QED和离子阱中直接测量双模Wigner函数的方案。
Australian Journal of Physics Pub Date : 2000-06-15 DOI: 10.1071/PH00004
Shi-Biao Zheng
{"title":"Scheme for direct measurement of the two-mode Wigner function in cavity QED and ion traps.","authors":"Shi-Biao Zheng","doi":"10.1071/PH00004","DOIUrl":"https://doi.org/10.1071/PH00004","url":null,"abstract":"A scheme is proposed for the reconstruction of two-mode entangled states in cavity QED and ion traps. For a two-mode field we show that the Wigner function can be obtained by measuring the probability of a two-level atom being in ground states after resonant interaction with two classical fields and dispersive interaction with the two-mode cavity field displaced by resonant sources. For the two-dimensional motion of a trapped ion the Wigner function is obtained by measuring the probability of the ion in its ground electronic state after displacing the ion motion and then resonantly exciting the ion.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126649094","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: 1
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