Evidence of the enhanced resonant tunneling effect in a triple-barrier heterostructure

The effect of properly lined-up quantum-well (QW) states, under an external bias, on the electron resonant tunneling is investigated in an InAlAs/InGaAs triple-barrier structure. The degree of alignment of two QW confined ground states at a resonant voltage is analyzed with low-temperature measurement. The experimental data shows the enhanced resonant tunneling effects, and proves that the second QW structure added to the InGaAs/ InAlAs double-barrier heterostructure can act as an effective tool for probing and extracting the resonant tunneling properties deep in a QW.     

Spin-dependent resonant tunneling in a periodic non-magnetic heterostructure with spin-orbit effects

We theoretically investigate the electron transport in a periodic non-magnetic heterostructure with both Dresselhaus and Rashba spin-orbit effects. We show that the transport properties obviously depend on the number of periods and the large spin polarization can be achieved in such a structure. We also show that for m>1, the resonance splitting occurs in the transmission curves of both spin-up and spin-down electrons when the transmission curves are plotted as a function of the electron energy or the well width.     

Theory of resonant photoemission in black phosphorus

Resonant photoemission in black phosphorus is studied theoretically with a model of simplified energy bands. It is shown that a core exciton state plays an essentially important role both in the resonant enhancement of the photoemission peak at the binding energy 10.8eV and the Fano type interference at 2.7eV, which have recently been observed experimentally.     

Theory of resonant electron scattering in amorphous metals

The crossover temperature T_K is calculated at which the motion of the tunneling atom and the conduction electron charge screening cloud is gradually coupled together. The first theoretical estimation is given to show that the formation of the resonance provides a realistic explanation for the electrical resistivity minimum and for the inelastic electron scattering rate relevant in localization theory if T_K ≈ 1 ? 5 K°.     

Theory of resonant forbidden Raman scattering in semiconductors

The Raman tensors for the electric field-induced and wavevector dependent scattering from LO phonons in semiconductors have been calculated near critical points using a perturbation treatment. The resulting expressions have analytic closed forms such that the dependence of the forbidden scattering intensity on the incident photon energy and the applied d.c. electric field can be evaluated from available energy band parameters. The forbidden LO scattering intensity of GaAs in the back scattering configuration has been numerically calculated near the e₁ and E₁ gaps as functions of the incident photon energy and the dc electric field. The result shows strong interference between the two scattering processes. The allowed TO and LO Raman scattering intensities of GaAs were also calculated at a wavelength of 1.06 μm from the SHG and Faust-Henry coefficients, and compared with the forbidden LO intensity.     

Detection of single photons by a resonant tunneling heterostructure with a quantum dot layer

Light absorption by GaAs/AlAs heterostructures with a layer of self-assembled InAs quantum dots (QDs) at resonant tunneling through an energy-selected QD has been investigated. A high sensitivity of the current through this selected tunneling channel to the absorption of single photons with a wavelength λ ≲ 860 nm up to a temperature of 50 K is demonstrated; this sensitivity is caused by the Coulomb effect of the photoexcited holes captured by surrounding QDs on the resonance conditions. It is shown that single-photon absorption can discretely change the current through the system under study by a factor of more than 50. The captured-hole lifetimes have been measured, and a model has been developed to qualitatively describe the experimental data. It is also demonstrated that the InAs monolayer can effectively absorb photons. The properties of the heterostructure studied can be used not only to detect photons but also to design logical valves and optical memory devices.     

Theory of indirect resonant inelastic X-ray scattering

We express the cross section for indirect resonant inelastic X-ray scattering in terms of an intrinsic dynamic correlation function of the system that is studied with this technique. The cross section is a linear combination of the charge response function and the dynamic longitudinal spin density correlation function. This result is asymptotically exact for both strong and weak local core-hole potentials. We show that one can change the relative charge and spin contribution to the inelastic spectral weight by varying the incident photon energy.     

Laser control of magneto-polaron in transition metal dichalcogenides triangular quantum well

We study the dynamic of magneto-polaron condensate in monolayer two dimensional (2D) transition metal dichalcogenides (TMDs) materials of 2H types in triangular quantum well potential. Within both the quantum mechanical Schrödinger approach (QMSA) and the improved Wigner-Brillouin theory (IWBT), Landau energies levels (LELs) are derived. We have shown that the magneto-polaron condensation is enhanced in monolayer MoSe₂ compared to MoS₂, WS₂ and WSe₂. We derive various levels by increasing a magnetic field and laser parameter. We show that the quantum confinement lifts the degeneracy of the Landau levels (LLs) resulting in an anticrossing and crossing. The dephasing effect due to the quantum well potential's parameter plays an important role in the magneto-polaron energy corrections, which are also affected by the amplitude of the laser field. The system presents Stückelberg oscillations which is important for practical applications.     

Weak-coupling expansion for the free energy of the magneto-polaron in two dimensions

Previous weak-coupling expansions of the ground-state energy for a Fröhlich type polaron in two dimensions subject to a perpendicular uniform magnetic field are extended to non-zero temperatures by using the path-integral representation. For every temperature the second-order contribution becomes positive for sufficiently high fields implying that a seemingly natural generalisation of the Jensen-Feynman inequality does not exist.     

Theory of four-photon scattering in conditions of intense resonant excitation

Journal of Applied Spectroscopy -     

Cyclotron resonance and screening effects in GaAs-GaAlAs heterojunctions

Cyclotron resonance absorption has been studied in several high quality GaAs-GaAlAs heterojunctions. The dependence of the effective mass upon frequency, electron concentration and temperature has been measured and gives a nonparabolicity that is some 20% smaller than that measured in bulk GaAs. This is contrary to simple theory which predicts an enhanced polaron contribution in two-dimensional systems, and we attribute this difference to strong screening of the electron-phonon interaction. The presence of a small magnetic field component parallel to the interface introduces a coupling at energies corresponding to the electric subband separations. These couplings have been studied as a function of electron concentration and the results interpreted in terms of changes in the depletion charge in the GaAs layer.     

Theory of resonant acoustic transmission through subwavelength apertures

A complete landscape is presented of the acoustic transmission properties of subwavelength apertures (slits and holes). First, we study the emergence of Fabry-Perot resonances in single apertures. When these apertures are placed in a periodic fashion, a new type of transmission resonance appears in the spectrum. We demonstrate that this resonance stems from the excitation of an acoustic guided wave that runs along the plate, which hybridizes strongly with the Fabry-Perot resonances associated with waveguide modes in single apertures. A detailed discussion of the similarities and differences with the electromagnetic case is also given.     

A study of estimation method for conduction band offset in semiconductor heterostructure by using triple-barrier resonant tunneling diodes

A method for evaluating a band offset of a heterojunction is proposed by measuring temperature dependence of current–voltage (I–V) characteristics in triple-barrier resonant tunneling diodes (TBRTDs). The method was applied for investigating a conduction band offset by using GaAs_0.25P_0.75/GaAs TBRTDs with thin strain heterobarriers grown by MOCVD and ΔE_c was estimated as 200–240 meV. In the strain-barrier TBRTDs, negative differential resistance was observed below 100 K.     

Thermoelectric power of GaAs-GaAlAs heterostructures in high magnetic fields

We report measurements of the diagonal component of the thermoelectric power in a superlattice and a heterojunction of GaAs and GaAlAs. The qualitative variation of the thermopower with magnetic field is in agreement with both theoretical studies and previous experimental measurements. Quantitatively, the behaviour of the superlattice agrees with calculations for an ideal two-dimensional system, but both the magnitude and temperature dependence of the thermopower in the heterojunctions cannot be explained by existing theories.