ترغب بنشر مسار تعليمي؟ اضغط هنا

Local electronic properties in nanoscale systems

42   0   0.0 ( 0 )
 نشر من قبل Andre Mauricio Conceicao Souza
 تاريخ النشر 2007
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

The local electronic structure on nanoscale chains is investigated theoretically. We propose a mechanism to explain the even-odd oscillation of length distribution of atom chains. We study the spatial peak structure as obtained by scanning tunneling microscopy (STM) constant-current topography as a function of the electron-electron interaction, band filling and temperature. The site-dependent magnetic moment is also examined.

قيم البحث

اقرأ أيضاً

77 - G. Lang , H.-J. Grafe , D. Paar 2009
The charge distribution in RFeAsO$_{1-x}$F$_x$ (R=La, Sm) iron pnictides is probed using As nuclear quadrupole resonance. Whereas undoped and optimally-doped or overdoped compounds feature a single charge environment, two charge environments are dete cted in the underdoped region. Spin-lattice relaxation measurements show their coexistence at the nanoscale. Together with the quantitative variations of the spectra with doping, they point to a local electronic order in the iron layers, where low- and high-doping-like regions would coexist. Implications for the interplay of static magnetism and superconductivity are discussed.
We investigate the electronic and structural changes at the nanoscale in vanadium dioxide (VO2) in the vicinity of its thermally driven phase transition. Both electronic and structural changes exhibit phase coexistence leading to percolation. In addi tion, we observe a dichotomy between the local electronic and structural transitions. Nanoscale x-ray diffraction reveals local, non-monotonic switching of the lattice structure, a phenomenon that is not seen in the electronic insulator-to-metal transition mapped by near-field infrared microscopy.
We calculate ground-state energies and density distributions of Hubbard superlattices characterized by periodic modulations of the on-site interaction and the on-site potential. Both density-matrix renormalization group and density-functional methods are employed and compared. We find that small variations in the on-site potential $v_i$ can simulate, cancel, or even overcompensate effects due to much larger variations in the on-site interaction $U_i$. Our findings highlight the importance of nanoscale spatial inhomogeneity in strongly correlated systems, and call for reexamination of model calculations assuming spatial homogeneity.
The crystal structures and the physical (magnetic, electrical transport and thermodynamic) properties of the ternary compounds CeRhSi2 and Ce2Rh3Si5 (orthorhombic CeNiSi2- and U2Co3Si5-type structures, respectively) were studied in wide ranges of tem perature and magnetic field strength. The results revealed that both materials are valence fluctuating systems, in line with previous literature reports. Direct evidence for valence fluctuations was obtained by means of Ce LIII-edge x-ray absorption spectroscopy and Ce 3d core-level x-ray photoelectron spectroscopy. The experimental data were confronted with the results of ab initio calculations of the electronic band structures in both compounds.
In the framework of ab initio dynamical mean field theory for realistic electronic structure calculations a new perturbation scheme which combine the T-matrix and fluctuating exchange approximations has been proposed. This method is less computationa lly expensive than numerically exact quantum Monte Carlo technics and give an adequate description of the electronic structure and exchange interactions for magnetic metals. We discuss a simple expression for the exchange interactions corresponding to the neglecting of the vertex corrections which becomes exact for the spin-wave stiffness in the local approximation. Electronic structure, correlation effects and exchange interactions for ferromagnetic nickel have been discussed.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا