Current volta voltage ev k 1 2 e f2 e f1 e wiederman

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Unformatted text preview: ↑ Peltier coefficien Heating and cooling of junctions, respectively, by (ΠA - ΠB)j if el. current. Volta voltage: eV K = Φ 1 − Φ 2 = E F2 − E F1 λE Wiederman-Franz law: σ = LT , S- 2 2 L = 2.45 × 10-8 WΩK-2 Summary n-semiconductor (p-semiconductor analogous) S- 3 2 Summary S- 4 2 Summary σ = e(nµn + pµp) n(T): strong exponential dependence µ(T): weak dependence, only matters in saturation range µ∝ T-3/2 scattering by phonons µ∝ T3/2 scattering by charged impurities Cf. metals: n(T) = const. σ(T) ∝ µ(T) Conduction electrons in magnetic field Lorentz force ⇒ • Orbit on surfaces E(k) = const. Metals: Fermi surfaces Semiconductors: surfaces E(k) = const near minimum of conduction band or maximum of valence band. • Orbits ⊥ B Orbital frequency: ωc = e B mc h 3 dA mc = , cyclotron mass, 2π dE S- 5 2 mc = m for free el. Summary Cyclotron resonance in HF field for ω = ωc ⇒ meff Landau levels: condensation of electrons on ″Landau tubes″ (1-dim. electron gas || B) ωc ∝ B ⇒ oscillations of D(EF) with B 1 h2 2 E = const + n + hω c + kz 2m 4243 1 3 2 1 2 B = (0, 0, Bz) ⇒ translational harmonic oscillator invatiance in z − direction Hall effect Electrons and holes experience same Lorentz force ⇒ for n = p only Hall voltage if µn ≠ µp 1 RH = − , n-semiconductor: ne S- 6 2 Summary 1 RH = − p-semiconductor: pe Diamagnetism Orbital momentum of electrons ⇒ magneti...
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This note was uploaded on 01/19/2010 for the course MATERIALS M504 taught by Professor Adelung during the Spring '02 term at Uni Kiel.

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