Cadmium telluride is a polar semiconductor

PHYSICS · Multi-part · Fermi University Physics · Condensed Matter, Materials & Soft Matter · Dielectric and optical properties of solids · Dielectric and optical properties of solids

Solid State Physics, Ch Collective and coupled excitations: plasmons, polaritons and polarons

Problem

Cadmium telluride is a polar semiconductor. Take

\varepsilon_\infty=7.1

\varepsilon_s=10.4

\hbar\omega_{LO}=21.1\,\mathrm{meV}

, and a conduction band mass, with the lattice held fixed, of

m^*=0.090\,m_e

. ((a)) Compute the Frohlich coupling constant

\alpha_F

. ((b)) Compute the weak-coupling polaron mass

m^{**}

and the percentage by which it exceeds

m^*

. Say which of the two masses a cyclotron-resonance experiment measures. ((c)) Gallium arsenide's polaron is

1.2\,\%

heavier than its band mass. Find which of the three inputs to

\alpha_F

chiefly accounts for the difference. ((d)) Classify the polaron as a single-particle, collective or coupled excitation, stating the criterion it meets, and say what the same formula predicts for silicon.

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