Magnetic transition and polaron crossover in a two-site single polaron model including double exchange interaction

A two-site double exchange model with a single polaron is studied using a perturbation expansion based on the modified Lang-Firsov transformation. The antiferromagnetic to ferromagnetic transition and the crossover from small to large polaron are investigated for different values of the antiferromagnetic interaction ($J$) between the core spins and the hopping ($t$) of the itinerant electron. Effect of the external magnetic field on the small to large polaron crossover and on the polaronic kinetic energy are studied. When the magnetic transition and the small to large polaron crossover coincide for some suitable range of $J/t$, the magnetic field has very pronounced effect on the transport.Comment: REVTEX and ps files, accepted in the European Physical Jour.

First excited state calculation using different phonon bases for the two-site Holstein model

The single-electron energy and static charge-lattice deformation correlations have been calculated for the first excited state of a two-site Holstein model within perturbative expansions using different standard phonon bases obtained through Lang-Firsov (LF) transformation, LF with squeezed phonon states, modified LF, modified LF transformation with squeezed phonon states, and also within weak-coupling perturbation approach. Comparisons of the convergence of the perturbative expansions for different phonon bases reveal that modified LF approach works much better than other approaches for major range of the coupling strength.Comment: 11 pages (REVTEX), 4 postscript figure

In-Vitro Anti-oxidant And Antimicrobial Study of Ficus Hispida

Ficus hispida L. belongs to the Moraceae family and is used by the maaiba trible (indigenous medicine - man of Manipur, India) as an indigenous traditional medicine. Present study deals with the successive extraction of the aerial parts of Ficus hispida and in-vitro screening of anti-oxidant and anti-microbial activity. The phytochemical screening of the methanol extract of Ficus hispida shows the presence of secondary metabolite groups like alkaloid, phenolic compounds, flavonoid, glycosides, protein etc. Phenolic compounds are commonly found in both edible and nonedible plants and are responsible for various medicinal activities of plants, so our study is based on determining antioxidant activity and anti-microbial activity. Beside these, we also measured the total flavonoid and total phenolic content of the respective sample to understand the effect of polyphenolic compound on different pathophysiological state associated with high free radical production. The in-vitro investigation proves the efficiency of this plant in various diseases states

Polaronic Heat Capacity in The Anderson - Hasegawa Model

An exact treatment of the Anderson - Hasegawa two - site model, incorporating the presence of superexchange and polarons, is used to compute the heat capacity. The calculated results point to the dominance of the lattice contribution, especially in the ferromagnetic regime. This behavior is in qualitative agreement with experimental findings.Comment: 9 pages, Revtex, 4 postscript figure

Spin-polaron model: transport properties of EuB6_6

To understand anomalous transport properties of EuB$_6$, we have studied the spin-polaron Hamiltonian incorporating the electron-phonon interaction. Assuming a strong exchange interaction between the carriers and the localized spins, the electrical conductivity is calculated. The temperature and magnetic field dependence of the resistivity of EuB$_6$ are well explained. At low temperature, magnons dominate the conduction process, whereas the lattice contribution becomes significant at very high temperature due to the scattering with the phonons. Large negative magnetoresistance near the ferromagnetic transition is also reproduced as observed in EuB$_6$.Comment: 4 pages, 3 figures, accepted in Phys. Rev.

Comparison of perturbative expansions using different phonon bases for two-site Holstein model

The two-site single-polaron problem is studied within the perturbative expansions using different standard phonon basis obtained through the Lang Firsov (LF), modified LF (MLF) and modified LF transformation with squeezed phonon states (MLFS). The role of these convergent expansions using the above prescriptions in lowering the energy and in determining the correlation functions are compared for different values of coupling strength. The single-electron energy, oscillator wave functions and correlation functions are calculated for the same system. The applicability of different phonon basis in different regimes of the coupling strength as well as in different regimes of hopping are also discussed.Comment: 24 pages (RevTEX), 12 postscript figures, final version accepted in PRB(2000) Jornal Ref: Phys. Rev. B, 61, 4592-4602 (2000

Participation of Muslim Female Students in Online Education: A Survey

Contemporary India is a primitive, patriarchal society of various feudal tribes. When we refer to caste in Considering the education system to be secular in the sense, when dealing with minority participation, we must bear in mind the debate expressed by Irfan Ahmed that “the characterization of minorities is not just numbers but a comparative and powerless position vis-a-vis the majority community in a given government” . Socio-religious issues dominate the understanding of minority female students and their participation in the education system while the existing considerations are subject to the internal affairs of the state; The current social conditions affected by the pandemic have changed and forced these conditions to be watched out for in order to create a global education system. Using qualitavie and survey research methods. This study aims to take advantage of this global space to investigate the participation status of Muslim female students and to identify areas for improvement