Ultra-low-temperature anomalies in heat capacities of metals caused by charge-density waves

A new fruitful area for low-temperature research is discussed. The contribution of phase excitations of incommensurate charge-density waves to the low-temperature heat capacities of metals is calculated, and the characteristic signature of phasons in calorimetric measurements is illustrated. The importance of anisotropy in the phason dispersion relation to the magnitude of the phason heat capacity and to the temperature at which the signature of the phasons can be seen is emphasized. Unless measurements are done at sufficiently low temperatures to freeze-out the phasons, it is possible to make significant errors in determining the electronic heat capacity. In particular the possibility of detecting phasons in potassium is discussed.