ترغب بنشر مسار تعليمي؟ اضغط هنا

A consistent interpretation of the low temperature magneto-transport in graphite using the Slonczewski--Weiss--McClure 3D band structure calculations

51   0   0.0 ( 0 )
 نشر من قبل Duncan Maude
 تاريخ النشر 2009
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

Magnetotransport of natural graphite and highly oriented pyrolytic graphite (HOPG) has been measured at mK temperatures. Quantum oscillations for both electron and hole carriers are observed with orbital angular momentum quantum number up to $Napprox90$. A remarkable agreement is obtained when comparing the data and the predictions of the Slonczewski--Weiss--McClure tight binding model for massive fermions. No evidence for Dirac fermions is observed in the transport data which is dominated by the crossing of the Landau bands at the Fermi level, corresponding to $dE/dk_z=0$, which occurs away from the $H$ point where Dirac fermions are expected.

قيم البحث

اقرأ أيضاً

Scaling of semiconductor devices has reached a stage where it has become absolutely imperative to consider the quantum mechanical aspects of transport in these ultra small devices. In these simulations, often one excludes a rigorous band structure tr eatment, since it poses a huge computational challenge. We have proposed here an efficient method for calculating full three-dimensionally coupled quantum transport in nanowire transistors including full band structure. We have shown the power of the method by simulating hole transport in p-type Ge nanowire transistors. The hole band structure obtained from our nearest neighbor sp3s* tight binding Hamiltonian agrees well qualitatively with more complex and accurate calculations that take third nearest neighbors into account. The calculated I-V results show how shifting of the energy bands due to confinement can be accurately captured only in a full band full quantum simulation.
We have made thermal and electrical transport measurements of uncompressed pyrolytic graphite sheet (uPGS), a mass-produced thin graphite sheet with various thicknesses between 10 and 100 {mu}m, at temperatures between 2 and 300 K. Compared to exfoli ated graphite sheets like Grafoil, uPGS has much higher conductivities by an order of magnitude because of its high crystallinity confirmed by X-ray diffraction and Raman spectroscopy. This material is advantageous as a thermal link of light weight in a wide temperature range particularly above 60 K where the thermal conductivity is much higher than common thermal conductors such as copper and aluminum alloys. We also found a general relationship between thermal and electrical conductivities in graphite-based materials which have highly anisotropic conductivities. This would be useful to estimate thermal conductance of a cryogenic part made of these materials from its electrical conductance more easily measurable at low temperature.
We present temperature-dependent magneto-transport experiments around the charge neutrality point in graphene and determine the amplitude of potential fluctuations $s$ responsible for the formation of electron-hole puddles. The experimental value $s approx 20$ meV is considerably larger than in conventional semiconductors which implies a strong localization of charge carriers observable up to room temperature. Surprisingly, in the quantized regime, the Hall resistivity overshoots the highest plateau values at high temperatures. We demonstrate by model calculations that such a peculiar behavior is expected in any system with coexisting electrons and holes when the energy spectrum is quantized and the carriers are partially localized.
The 2D Fermi surface of 1st stage PdAl2Cl8 acceptor-type graphite intercalation compounds (GICs) has been investigated using the Shubnikov-de Haas (SdH) effect. One fundamental frequency is observed, the angular variation of which confirms its strong ly 2D nature, as previously found through electrical conductivity measurements. The energy spectrum can be described by the 2D band structure model proposed by Blinowski et al. We obtain the following parameter values: intraplane C-C interaction energy gamma_0 = 2.7 eV, Fermi energy E_F = -1.1 eV and carrier density n_SdH= 1.1x10^27 m^-3. Some fewer details are presented on stage 2 and 3 materials.
Contents: (1) Model of a lateral quantum dot system (2) Thermally-activated conduction: onset of the Coulomb blockade oscillations and Coulomb blockade peaks at low temperature (3) Activationless transport through a blockaded quantum dot: inela stic and elastic co-tunneling (4) Kondo regime in transport through a quantum dot: effective low-energy Hamiltonian; linear response; weak coupling regime; strong coupling regime; beyond linear response; splitting of the Kondo peak in a magnetic field; Kondo effect in quantum dots with large spin.
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