Collective behavior in solids and materials.
Answer five questions about Condensed Matter Physics and get instant feedback.
A tiny packet of vibration energy that moves through a crystal and can carry heat
Phonons come in many 'notes' (frequencies), and scattering between them or off defects largely controls a solid's thermal conductivity, which is why crystals and glasses conduct heat so differently.
What happens when a small change in temperature or pressure causes a big change in material behavior?
At the transition point, materials can absorb or release lots of energy as latent heat without changing temperature, like ice melting at $0\,\text{C}$, and properties can flip suddenly.
What changes with wavelength in a crystal, forming a dispersion relation?
Plotting frequency versus wavevector reveals acoustic and optical branches; near $k=0$, the slope gives the sound speed, and flat regions near the Brillouin-zone edge signal low group velocity.
What is an energy range with no allowed states, so conduction needs enough energy to cross it?
In semiconductors, tiny amounts of doping can create states near the band edges, letting the Fermi level shift and dramatically change conductivity without altering the crystal.
This image question appears in the interactive quiz.
Magnetic domains reduce energy by grouping aligned atomic moments into neighboring regions.
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