The temperature dependence of both components of the resistivity tensor ̺xx(T ) and ̺xy(T ) has been studied at T ≥ 4.2 K within IQHE plateaux around filling factors ν=2 and ν=4 of medium-mobility GaAs/AlGaAs heterostructures. In the middle of the mobility gap standard activated conductivity has been found with activation energies ∆ scaling well with h̄ωc/2 . At filling factors slightly below ν=2 ...

The suppression of transverse phonons by liquidlike diffusion in superionic conductors has been proposed as a means to dramatically reduce thermal conductivity in thermoelectric materials [H. Lui et al. Nat. Mater. 11, 422 (2012)NMAACR1476-112210.1038/nmat3273]. We have measured the ion transport and lattice dynamics in the original phonon-liquid electron-crystal Cu_{2}Se using neutron spectros...

We have measured the complex conductivity sigma(xx) of a two-dimensional electron system in the quantum Hall regime up to frequencies of 6 GHz at electron temperatures below 100 mK. Using both its imaginary and real part we show that sigma(xx) can be scaled to a single function for different frequencies and several transitions between plateaus in the quantum Hall effect. Additionally, the condu...

A temperature-induced crossover from hopping to metallic conductivity is observed for barely insulating samples of Ge:As and Ge:Sb with impurity concentration N just below the critical value Nc0. The values of the correlation length ξ are obtained on both sides of the transition. A method is developed for determination of a ‘delocalization temperature’ Td , which separates the hopping and metal...