poplaqatar.blogg.se

Here we give a thermodynamic analysis that confirms the negative-temperature interpretation of the Purcell-Pound experiments.

Negative absolute temperatures were introduced into experimental physics by Purcell and Pound, who successfully applied this concept to nuclear spins nevertheless, the concept has proved controversial: a recent article aroused considerable interest by its claim, based on a classical entropy formula (the "volume entropy") due to Gibbs, that negative temperatures violated basic principles of statistical thermodynamics. Physics of negative absolute temperatures. The results are explained by directional scattering of electrons in two dimensions. The observed reversal of the current or potential in the middle terminal is interpreted as the analog of Bernoulli's effect in a Fermi liquid. The device displays momentum and current transfer ratios that far exceed unity. A three-terminal device formed by two electrostatic barriers crossing an asymmetrically patterned two dimensional electron gas displays an unusual potential depression at the middle contact, yielding absolute negative resistance. However, as the electron energies increased, in the intermediate regime, single or few intercarrier scattering events starts to dominate the transport properties of a conductor with sufficiently small dimensions. Intercarrier scattering does not influence the conductivity of the latter transport regime and does not exist in the former. The results are explained by directional scattering of electrons in two dimensions.Ī ballistic conductor is restricted to have positive three terminal resistance just as a Drude conductor. The observed reversal of the current or potential in the middle terminal can be interpreted as the analog of Bernoulli’s effect in a Fermi liquid. Absolute Negative Resistance Induced by Directional Electron-Electron Scattering in a Two-Dimensional Electron GasĪ three-terminal device formed by two electrostatic barriers crossing an asymmetrically patterned two-dimensional electron gas displays an unusual potential depression at the middle contact, yielding absolute negative resistance.