The Coulomb drag between two spatially separated one-dimensional (1D) electron systems in lithographically fabricated 2 µm long quantum wires is studied experimentally. The drag voltage V D shows peaks as a function of a gate voltage which shifts the position of the Fermi level relative to the 1D subbands. The maximum in V D and the drag resistance R D occurs when the 1D subbands of the wires are aligned and the Fermi wave vector is small. The drag resistance is found to decrease exponentially with interwire separation. In the temperature region 0.2 K T 1 K, R D decreases with increasing temperature in a power-law fashion R D ∝ T x with x ranging from −0.6 to −0.77 depending on the gate voltage. We interpret our data in terms of the Tomonaga-Luttinger liquid theory.

Our experimental studies of electron transport in wide (14 nm) HgTe quantum wells confirm the persistence of a two-dimensional topological insulator state reported previously for narrower wells, where it was justified theoretically. Comparison of local and nonlocal resistance measurements indicate edge state transport in the samples of about 1 mm size at temperatures below 1 K. Temperature dependence of the resistances suggests an insulating gap of the order of a few meV. In samples with sizes smaller than 10  μm a quasiballistic transport via the edge states is observed.

We present experimental and theoretical studies of the magnetoresistance oscillations induced by resonance transitions of electrons between tunnel-coupled states in double quantum wells. The suppression of these oscillations with increasing temperature is irrelevant to the thermal broadening of the Fermi distribution and reflects the temperature dependence of the quantum lifetime of electrons. The gate control of the period and amplitude of the oscillations is demonstrated.Comment: 5 pages 4 figures, to be published in the Physical Review

The dynamic ͑ac͒ conductivity tensor of quantum wells with two populated subbands in the presence of a magnetic field perpendicular to the well layer is calculated theoretically. The microscopic theory is based on the Kubo formalism assuming a detailed consideration of elastic scattering of electrons by the random disorder potential with arbitrary correlation length. The results describe the influence of magnetic field on the linear absorption of low-frequency electromagnetic radiation, and demonstrate the existence of magnetic oscillations that survive at high temperatures and whose maxima correspond to absorption of electromagnetic radiation at combined frequencies, determined by both the magnetic field and the subband separation. Different polarizations of the radiation field with respect to the quantum-well layer are considered. Analytical expressions are derived for the case of sufficiently weak magnetic field when the Landau levels are overlapping. Application of the theory to the static ͑dc͒ limit provides a consistent description of the magneto-intersubband oscillations of the resistivity in the systems with two populated subbands.

Magnetotransport measurements on a high-mobility electron bilayer system formed in a wide GaAs quantum well reveal vanishing dissipative resistance under continuous microwave irradiation. Profound zero-resistance states (ZRS) appear even in the presence of additional intersubband scattering of electrons. We study the dependence of photoresistance on frequency, microwave power, and temperature. Experimental results are compared with a theory demonstrating that the conditions for absolute negative resistivity correlate with the appearance of ZRS.