The Copper Fermi Surface

Plate 57 speaks for itself: “Sphere with necks.”

The Physics

Copper's conduction electrons fill a nearly spherical Fermi surface, but it bulges out to touch the Brillouin zone faces along ⟨111⟩, forming necks. Pippard mapped it in 1957.

E_F = ħ² k_F² / (2 m)

• E_F: Fermi energy, J (quoted in eV)
• ħ: reduced Planck constant, J s
• k_F: Fermi wavevector, m⁻¹
• m: electron mass, kg

Free-electron model: E_F ≈ 7.0 eV. Necks reach the zone faces along ⟨111⟩.

Sources

• A. B. Pippard, Phil. Trans. R. Soc. A 250, 325 (1957).
• N. W. Ashcroft, N. D. Mermin, Solid State Physics, Table 2.1.

On the poster

Plate 057, “The Copper Fermi Surface”: the pixel-art plate with its slogan “Sphere with necks.”, the key equation and the facts panel shown above. Pixelated Physics. Physics. Personified.