E. V. Bogdanov

SmB6 at high pressures: The transition from insulating to the metallic Kondo lattice

Abstract Temperature dependences of the resistivity have been studied in SmB 6 at pressures p ≲120 kbar. The suppression of the gap and the transition to the metallic conductivity observed at p ≳55 kbar is explained within the framework of the model which treats SmB 6 at p =0 as well as SmS at 6 kbar ≲ p ≲ 19 kbar as insulating Kondo lattices with JJ c and n m =1. We also report here preliminary results on SmB 6 current-voltage characteristics, and on magnetic ( H-T ) phase diagrams of CeB 6 at pressures p ≲11 kbar.

Electroluminescence and band structure in p-Al x Ga1−x As/GaAs1−y P y /n-Al x Ga1−x As under uniaxial compression

Band structure calculations in p-Al x Ga1−x As/GaAs1−y P y /n-Al x Ga1−x As heterostructure under uni-axial compression in the 1 1 0 direction indicates an increase in the optical energy gap with dE ph/dP ≈ 85 meV GPa−1, a decrease in the quantum well barriers and light hole–heavy hole crossover at uniaxial stress P ≈ 450–500 MPa. The observed increase in electroluminescence intensity and photon energy shift under uni-axial compression are explained by numerical calculation data.

Method for elastic uniaxial stress of single crystals: description and applications

The original method for a strong elastic uniaxial compression of single crystals up to 5 ÷ 6 kbar, calibration procedure and its applications for semimetal and semiconductor samples are described in details for the first time. This method simplifies sample installation and adjustment; it prevents the frequent destruction of samples, which often takes place in conventional methods of uniaxial compression between two anvils.

The emission spectrum of p-AlGaAs/GaAsP/n-AlGaAs diodes under uniaxial compression

AbstractNew experimental data are presented on the effects of uniaxial compression of up to 4 kbar along the [110] and [1

Uniaxial compression influence on electroluminescence spectra in p-Al x Ga1−x As/GaAs1−y P y /n-Al x Ga1−x As heterostructures

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Relaxation of low-temperature negative photoconductivity in p-GaAs/Al0.5Ga0.5As under normal and uniaxially stressed conditions

0] crystallographic directions on the spectra of electroluminescence and the current-voltage characteristics of diodes based on n-AlxGa1 − xAs/GaAsyP1 − y/p-AlxGa1 − xAs (y = 0.84) heterostructures that were designed for injection lasers. With increasing pressure, the spectra show a shift to shorter wavelengths, reaching 25 meV at 3 kbar; the intensity increases 2–3 times as well. Numerical calculations were carried out on the band structure of the investigated heterostructures under compression along the [110] axis, which indicate the increase in the effective band gap in the quantum well (QW) GaAsyP1 − y, with a pressure coefficient of about 8.5 meV/kbar and reduction of the barrier height at the boundaries of the QW. The calculations predict the possibility that light and heavy holes crossover at pressures above 4.5–5 kbar. The increase in the effective band gap completely describes the experimental data on the shift of the electroluminescence spectra. The mixing of light and heavy holes when approaching the band crosspoint is the probable cause of an increase in the intensity of radiation under uniaxial compression.

Pressure dependence of 2D hole mobility in thermoactivated photoconductivity effect observed in p‐GaAs/Al0.5Ga0.5As heterostructures

The band structure, size quatized levels, and wave functions in the conduction and valence bands of strained n-AlxGa1 − xAs/GaAsyP1 − y/p-AlxGa1 − xAs (y = 0.84) heterostructures are calculated numerically upon a uniaxial compression along the [110] direction. The calculation indicates a sublinear increase of the effective optical gap in the GaAs0.84P0.16 quantum well, strong mixing of states of light and heavy holes, and merging of the corresponding ground states in the quantum well of the valence band under a pressure of 4.5–5 kbar. The calculation of matrix elements of the electron-photon interaction operator for a system of possible interband transitions permits one to determine the optical gain for the TE and TM modes. The increase in this coefficient by two to fourfold under uniaxial compression agrees with the previously published experimental data on the increase of the electroluminescence intensity.

Pressure Dependence of the Direct Energy Gap in Bi1‐xsbx Semiconductor Alloys

We present new results on the influence of uniaxial stress up to P=400 MPa along [110] direction on the electroluminescence (EL) spectra of p-Al x Ga1−x As/GaAs1−y P y /n-Al x Ga1−x As double heterostructures. With increasing stress, the emission spectra demonstrate a blue shift of up to 20 meV at a pressure of P=400 MPa, while the EL intensity increases under compression. The results are discussed in terms of changes in the band structure under uniaxial compression.