We have measured the temperature dependence of the conductance of long V-groove quantum wires fabricated using GaAs/AlGaAs heterostructures, in a wide temperature range (200 mK < T < 4.2 K). We find that for our quantum wires the Fermi velocity can be as low as nu(F) congruent to 5 x 10(4) m/s, corresponding to an interaction parameter value of g congruent to 0.56. This value suggests that our data are consistent with theories developed within the framework of the Luttinger liquid model in the presence of a single strong barrier (weak link).

When odd multiples of half flux quanta thread a cylindrical superconducting shell with a diameter d shorter than the zero temperature coherence length ξ(0), superconductivity is predicted to be destroyed. We show here that as d is reduced in comparison to ξ(0) the resistance attains the normal state value, which seems to be temperature independent in the vicinity of half flux quanta. The data are in agreement with recent theoretical results.

The sheet resistance as a function of temperature, magnetic field and its orientation for atomically flat SrTiO3/LaAlO3 interfaces with carrier densities of similar to 3 x 10(13) cm(-2) is reported. At low magnetic fields superconductivity is observed below 130 mK. The temperature dependence of the high field magnetoresistance and its strong anisotropy suggest possible magnetic ordering below 35 K. The origin of this ordering and its possible relation to superconductivity are discussed.

This chapter gives an experimental observation on the transport properties of long GaAs quantum wires. The transport properties of a wire strongly depend on temperature and wire length. Due to interactions between electrons, the conductance is predicted to decrease with temperature, as predicted by the Luttinger liquid model, with power-law dependences obtained in the limits of both weak and strong scatterers. Moreover, localization effects, as predicted by the many impurities theory, are expected to be relevant for wires containing a larger number of impurities or only at sufficiently low temperatures, even for macroscopically long wires. Controlled Vocabulary Terms Luttinger liquid; quantum wires

We report sub-meV (as low as 0.6meV) low-temperature photoluminescence linewidth and high low-temperature electron mobility (μ∼1−1.5×106cm2∕Vs) of GaAs quantum wells in AlGaAs barriers grown by standard metalorganic vapor phase epitaxy. These records values are achieved by epitaxial growth on (100) slightly misoriented substrates [⩽0.6 degrees off-(100) GaAs substrates] in combination with a high V/III ratio for AlGaAs growth. Such small misorientations are sufficient to drastically modify the optical and transport properties as well as the growth mode and surface morphologies of both GaAs and AlGaAs epitaxial layers, allowing greater interface quality and reduced impurity incorporation. The quantum wells so obtained show optical properties comparable to high-quality samples grown by molecular beam epitaxy. In addition, the slight misorientation considerably reduces the impact of substrate temperature on electron mobility, which allows achieving high values of μ within a much broader range of growth temperatures.

We have measured the temperature dependence of the conductance in long V-groove quantum wires fabricated in GaAs/AlGaAs heterostructures. Our data are consistent with recent theories developed within the framework of the Luttinger-liquid model, in the limit of weakly disordered wires. We show that, for the relatively low level of disorder in our quantum wires, the value of the interaction parameter g congruent with 0.66, which is the expected value for GaAs. However, samples with a higher level of disorder show conductance with stronger temperature dependence, which does not allow their treatment in the framework of perturbation theory. Fitting such data with perturbation-theory models leads inevitably to wrong (lower) values of g.