Superfluid density in the underdoped YBa2Cu3O7-x: evidence for d-density-wave order of the pseudogap

The investigation of the penetration depth lambda(ab)(T,p) in YBa2Cu3O7-x crystals allowed one to observe the following features of the superfluid density n(s)(T,p) proportional, variant lambda(-2)(ab)(T,p) as a function of temperature T0) depends on p slightly in the optimally and moderately doped regions (0.10相似文献   

Measurement of cyclotron masses of spin-orbit-split quasi-two-dimensional holes in GaAs(100) narrow quantum wells

The magnetic field dependence of the cyclotron mass of heavy holes in asymmetric GaAs(100) quantum wells is measured by optical detection of resonant microwave absorption for various concentrations of quasi-two-dimensional holes. The effect of spin-orbit splitting on the cyclotron masses of heavy holes is discovered and investigated. The energy spectrum of holes is calculated on the basis of experimental data. The energy range in which spin-plasmon oscillations are observed in hole systems with various concentrations is predicted.     

Non-Contradictory Aggregation of Strict Order Relations

We study the problem of collective choice. The profile of individual preferences of experts is defined by relations of strict order. A non-contradictory aggregate preference relation is based on the weighted majority graph that characterizes the degree of superiority of one alternative over another. The aggregate relation also defines a strict order and satisfies requirements to group decisions, namely, the monotony, the preservation of the Pareto relation, the minimality of the distance to expert preferences.     

Electron paramagnetic resonance study of the nuclear spin dynamics in an AlAs quantum well

The nuclear spin dynamics in an asymmetrically doped 16-nm AlAs quantum well grown along the [001] direction has been studied experimentally using the time decay of the Overhauser shift of paramagnetic resonance of conduction electrons. The nonzero spin polarization of nuclei causing the initial observed Overhauser shift is due the relaxation of the nonequilibrium spin polarization of electrons into the nuclear subsystem near electron paramagnetic resonance owing to the hyperfine interaction. The measured relaxation time of nuclear spins near the unity filling factor is (530 ± 30) min at the temperature T = 0.5 K. This value exceeds the characteristic spin relaxation times of nuclei in GaAs/AlGaAs heterostructures by more than an order of magnitude. This fact indicates the decrease in the strength of the hyperfine interaction in the AlAs quantum well in comparison with GaAs/AlGaAs heterostructures.     

Renormalization of the Effective Electron Mass Governing the Period of Microwave-Induced Resistance Oscillations in ZnO/MgZnO Heterojunctions

The phenomenon of microwave-induced magnetoresistance oscillations is studied in a series of ZnO/MgZnO heterojunctions characterized by different two-dimensional electron densities n. It is found that the effective electron mass m* determined from the period of microwave-induced magnetoresistance oscillations depends essentially on this parameter. For high densities, the value of m* tends to the effective electron mass in bulk ZnO, while for low densities, m* increases pronouncedly and becomes considerably larger than the electron cyclotron mass. The experimental results give clear evidence of a significant impact of the electron–electron interaction on microwave-induced magnetoresistance oscillations.     

c-axis penetration depth in Bi2Sr2CaCu2O8+δ single crystals measured by ac-susceptibility and cavity perturbation technique

The c-axis penetration depth Δλ_c in Bi₂Sr₂CaCu₂O_8+δ (BSCCO) single crystals as a function of temperature has been determined using two techniques, namely, measurements of the ac-susceptibility at a frequency of 100 kHz and the surface impedance at 9.4 GHz. Both techniques yield an almost linear function Δλ_c(T)∝T in the temperature range T<0.5T _c. Electrodynamic analysis of the impedance anisotropy has allowed us to estimate λ_c(0)≈50 µm in BSCCO crystals overdoped with oxygen (T _c≈84 K) and λ_c(0)≈150 µm at the optimal doping level (T _c≈90 K).     

Contactless Observation of Microwave Induced Resistance Oscillations in ZnO/MgxZn1 – xO Heterojunction

JETP Letters - In high-quality ZnO/MgxZn1 – xO heterojunctions, microwave-induced magnetoresistance oscillations have been investigated using a contactless technique. The basic detection...     

Study of the Radiation Capability of a Perfectly Conducting Half-Plane Excited by a Slot Perpendicular to the Conductor Edge

Radiophysics and Quantum Electronics - We solve the problem of excitation of an infinite, perfectly conducting half-plane by an external field in the slot line, which is perpendicular to the edge...     

Observation of Electron Spin Resonance in the Microwave-Induced Photovoltage

JETP Letters - The microwave-induced photovoltage in two-dimensional electron systems in an AlAs quantum well and a ZnO/MgZnO heterojunction under the conditions of the quantum Hall effect is...     

Spin relaxation in GaAs/AlGaAs quantum wells in the vicinity of odd filling factors

Electron spin resonance in GaAs/AlGaAs quantum wells in the vicinity of odd filling factors ν = 3, 5, and 7 is investigated. The spin relaxation time of two-dimensional electrons is determined from the width of the microwave resonance absorption line. Dependences of the spin relaxation time on the filling factor, temperature, and orientation of the magnetic field are investigated. The spin relaxation time decreases noticeably upon deviation from odd filling factors, and its maximum value depends on the angle between the magnetic field and the plane of the two-dimensional electron gas.