DHVA magnetic susceptibility of a 2D free electron gas

Summary The grand potential and energy of a noninteracting uncorrelated two-dimensional electron gas subject to Landau quantization in a magnetic field are examined here at low temperatures. The DeHaas-Van Alphen oscillatory magnetic susceptibility for the free 2D gas is calculated and the results presented here incorporate the effects of spin (by allowing that spin splitting may not, in general, equal Landau level separation) in formulae that have the same analytic structure for both even and odd numbers of filled Landau levels.

---

Riassunto Il gran potenziale e l'energia di un gas elettronico bidimensionale non correlato non interagente, soggetto a quantizzazione di Landau in un campo magnetico, sono esaminate qui a basse temperature. La suscettibilità magnetica oscillatoria di De Haas-Van Alphen per il gas libero 2D è calcolata e i risultati presentati qui incorporano gli effetti di spin (tenendo conto che il taglio di spin non può, in generale, eguagliare uguale separazione del livello di Landau) in formule che hanno la stessa struttura analitica per numeri sia pari che dispari dei livelli completi di Landau.

---

Резюме В зтой работе при низких температурах исследуется потенсиал и знергия невзаимодействующего некоррелированного двумерного злектроннного газа, подчинющегося квантованию Ландау в магнитном поле. Вычисляется осцилляторная магнитная восприимчивость де Гааза-ван Альфена для свободнго двумерного газа. Полученные результаты учитывают спиновые зффекты (допуская, что спиновое расщепление в общем случае может быть не равно интервалу между уровнями Ландау) в формулах, которые имеют ту же аналитическую структуру для четного и нечетного числа заполненных уровней Ландау.

     

Dynamical exchange corrections to the dielectric function in a two-dimensional electron gas

The effect of dynamical exchange interactions on the dielectric function of a two-dimensional electron gas is studied using a variational approach. Exchange effects are introduced via the local-field correction. The variationally obtained local-field factor is compared to the earlier perturbative result to first order in the electron-electron interaction.     

Dynamical exchange corrections to the dielectric function in a two-dimensional electron gas

The effect of dynamical exchange interactions on the dielectric function of a two-dimensional electron gas is studied using a variational approach. Exchange effects are introduced via the local-field correction. The variationally obtained local-field factor is compared to the earlier perturbative result to first order in the electron-electron interaction.     

On the paramagnetic and diamagnetic susceptibility of nuclei

Measured M1 ground state transition strengths over a wide range of nuclei are used for a determination of the paramagnetic susceptibility of nuclei. The diamagnetic susceptibility can at present only be estimated.     

On the finite size corrections to some random matching problems

We get back to the computation of the leading finite size corrections to some random link matching problems, first adressed by Mézard and Parisi [J. Phys. France 48, 1451 (1987)]. In the so-called bipartite case, their result is in contradiction with subsequent works. We show that they made some mistakes, and correcting them, we get the expected result. In the non bipartite case, we agree with their result but push the analytical treatment further. Received 28 April 2002 Published online 14 October 2002 RID="a" ID="a"e-mail: giorgio.parisi@roma1.infn.it RID="b" ID="b"e-mail: matthieu.ratieville@roma1.infn.it     

From spin flip excitations to the spin susceptibility enhancement of a two-dimensional electron gas

The g-factor enhancement of the spin-polarized two-dimensional electron gas was measured directly over a wide range of spin polarizations, using spin flip resonant Raman scattering spectroscopy on two-dimensional electron gases embedded in Cd(1-x)Mn(x)Te semimagnetic quantum wells. At zero Raman transferred momentum, the single-particle spin flip excitation, energy Z*, coexists in the Raman spectrum with the spin flip wave of energy Z, the bare giant Zeeman splitting. We compare the measured g-factor enhancement with recent spin-susceptibility enhancement theories and deduce the spin-polarization dependence of the mass renormalization.     

Finite width and local field corrections to spin coulomb drag in a quasi-two-dimensional electron gas

We study the spin Coulomb drag in a quasi-two-dimensional electron gas of finite transverse width, including local field corrections beyond the random phase approximation (RPA). We find that the finite transverse width of the electron gas causes a significant reduction of the spin Coulomb drag. This reduction, however, is largely compensated by the enhancement coming from the inclusion of many-body local field effects beyond the RPA, thereby restoring good agreement with the experimental observations by C. P. Weber et al. [Nature (London) 437, 1330 (2005)].     

Orbital susceptibility of the low density electron gas

The orbital susceptibility of the electron gas is calculated at densities so low that the ‘Wigner crystal’ picture is valid. These results are used to construct an interpolation for the orbital susceptibility which is exact in the high density limit and nearly exact at low densities.     

Local diamagnetic susceptibility of quasi-two-dimensional graphite

A sample of quasi-two-dimensional graphite (QTDG) whose magnetic properties are described within the Dirac fermion model is investigated by the nuclear magnetic resonance (NMR) and scanning tunneling microscopy (STM) techniques. The broad spectrum of the sample points to a large dispersion of crystallite sizes in this system, which is also confirmed by STM data. It is established that the local diamagnetic susceptibility may substantially exceed the average value over the sample and reaches an abnormally high value of ?1.3 × 10^?4 emu/g at T = 4.2 K, which is greater than the corresponding value of highly oriented graphite by a factor of four.     

对气体涨落的修正

在研究气体小体积元的涨落时,传统的关于大系统的平衡涨落结果是不够的.本文首先利用平均自由程方法说明了相邻的小单元之间由关联导致的对气体涨落修正的物理机制,然后运用气体输运方法计算了精确的修正结果.     

Correlation between diamagnetic susceptibility and electron spin resonance feature for various multiwalled carbon nanotubes

Determination of the structural features is a fundamental subject in nanotube research. A simple method is proposed to evaluate the structure of multiwalled carbon nanotubes (MWNTs) having either the concentric or the scrolled structure. Although transmission electron microscopy and Raman scattering did not indicate a distinct difference in the structural features of the MWNTs, the temperature dependence of the diamagnetic susceptibility showed a clear difference; one was temperature-independent constant diamagnetism and the others indicated temperature-dependent diamagnetic susceptibilities with different magnitudes. The former phenomenon can be explained by applying the nested concentric nature to the MWNTs, and the latter by the scrolled nature. The difference in the magnitude of the temperature dependence is evidence for the mixed nature of the concentric and scrolled structures. PACS 61.46.Fg; 75.75.+a; 76.30.Pk; 78.67.Ch; 81.07.De     

On the coherent states of a free electron laser

The coherence properties of the Free Electron Laser are examined both in the single mode and multimode case.     

Diamagnetic susceptibility of the electron gas in the cylindrical nanolayer

Diamagnetic properties of the electron gas in cylindrical nanolayer have been investigated. The dependence of mean energy, mean magnetization and mean magnetic susceptibility on the values of magnetic field is obtained. Comparison of these dependencies with the case, when the electron gas is localized in the cylindrical quantum dot, is carried out. In a nanolayer, the character of an effect of size quantization on the magnetic properties of the electron gas has been revealed.     

Nonadiabatic theory of diamagnetic susceptibility of molecules

A nonadiabatic theory of diamagnetic susceptibility of molecules is presented in which the electrons and nuclei are considered to be a united system of charged particles whose motion is simultaneously per-turbed by a magnetic field. It is found that on separating out the translational motion of the molecule as a whole, there is certain freedom in choosing the phase of the wave function. Its optimum choice corresponds to the gauge of the vector potential with which two contributions opposite in sign to the magnetic susceptibility—the first order diamagnetism and the second order paramagnetism—have minimum magnitudes. Expressions for non-adiabatic calculations of the diamagnetic susceptibility of atoms and molecules are derived. The diamagnetic contributions to the energy of the hydrogen, helium, and lithium atoms, the hydrogen molecule, the π^?μ^?π⁺μ⁺ and p ^? K ^? p ⁺ K ⁺ mesomolecules, and the positronium molecule e ^? e ^? e ⁺ e ⁺ are calculated. The nonadiabatic contribution of the nuclear motion to the diamagnetic susceptibility amounts to 0.01–0.1% for ordinary atoms and molecules, is increased by several hundred times on passing to mesomolecules, and reaches 50% for the positronium molecule.     

Quantum corrections to the energy density of a homogeneous Bose gas

Quantum corrections to the properties of a homogeneous interacting Bose gas at zero temperature can be calculated as a low-density expansion in powers of , where is the number density and a is the S-wave scattering length. We calculate the ground state energy density to second order in . The coefficient of the correction has a logarithmic term that was calculated in 1959. We present the first calculation of the constant under the logarithm. The constant depends not only on a, but also on an extra parameter that describes the low energy scattering of the bosons. In the case of alkali atoms, we argue that the second order quantum correction is dominated by the logarithmic term, where the argument of the logarithm is ,and is the length scale set by the van der Waals potential. Received 2 February 1999     

On the Coulomb energy of a finite-temperature electron gas

We rederive the Coulomb expansion of the electron gas average energy at finite temperature, starting from scratch, i.e., using only the framework of the grand canonical ensemble and not the finite-T Green's function formalism. We recover the analytical expressions of the exchange and correlation energy in both the high-T and theT=0 limits. We explicitly show the origin of the crossover of the correlation energy leading term frome ⁴ lne ² at zero temperature toe ³ at finiteT. We also discuss the relative importance of exchange and correlation in both limits.