Effect of uniaxial mechanical stress on Shubnikov-de Haas oscillations in hole channels of silicon field-effect transistors

A study is made of the effect of uniaxial mechanical stress on Shubnikov-de Haas oscillations in two-dimensional hole channels of silicon field-effect transistors. It is shown that the main effect of the stress is a shift of the node of the beats of the oscillations. This shift corresponds in the case of compression (tension) to an increase (decrease) of the spin splitting in a zero magnetic field. In the case of two filled size-quantization subbands a mechanical stress of either sign causes a small fraction of the carriers to be transferred from the lower into the upper subband. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 9, 630–635 (10 November 1996)     

Comparison of Shubnikov-de Haas effect and cyclotron resonance on Si(100) MOS transistors under uniaxial stress

The stress induced population of the non-equivalent subbands E₀ to E′₀ is investigated by measurements of the magnetoconductivity — the Shubnikov-de Haas oscillations — and the cyclotron resonance taken on the same MOS transistor under identical conditions. In cyclotron resonance with increasing stress, a gradual transfer of carriers from E₀ to E′₀ is observed, whereas the Shubnikov-de Haas periodicity is unaffected and always yields a valley degeneracy of two. A domain model is required to resolve this apparent discrepancy.     

Shubnikov-de Haas oscillations in p-type inversion layers on n-type silicon

Surface Shubnikov-de Haas oscillations have been measured in p-type channels of (110) silicon field effect transitors between 1.4 and 4.2 K in magnetic fields up to 10 Tesla. Two electric subbands were revealed and the effective masses of the holes in both bands could be determined. For one subband the dependence of the mass on the surface electric field was investigated. At low gate voltages the g-factor of the holes was measured from the spin splitting of the Landau-levels.     

Shubnikov-de Haas effect in Bismuth in high magnetic fields

Shubnikov-de Haas effect in Bi was observed in pulsed high magnetic fields up to 420 kG. Hole resonances were observed up to the second (N = 1) and the third (N = 2) peaks for the magnetic fields along the bisectrix and the binary axes, respectively. From the analysis of the resonant magnetic fields, changes of the Fermi level and the carrier concentration were calculated. The field at which the semimetal to semiconductor transition will occur was estimated as 850 kG ∽ 1 MG for the field direction parallel to the binary axis. Anomalously large decrease of the magnetoresistance was observed above 300 kG.     

Shubnikov-de Haas effect on conductance fluctuations in two-dimensional random magnetic fields

Conductance fluctuations in two-dimensional random magnetic fields are investigated numerically in the case where the mean and the fluctuation of the random magnetic fields are of the same order. The conductance is evaluated by means of the Landauer formula. It is found that for a system with edge states, the conductance fluctuation exhibits clearly a Shubnikov-de Haas type oscillation in the weak field regime.     

Shubnikov-de Haas effect and effective mass inn-InP in dependence on carrier concentration

Shubnikov-de Haas investigations onn-InP are presented and the effective mass as a function of carrier concentration is determined. The experiments are carried out with bulk and liquid phase epitactically grown material and carrier concentrations betweenn=10¹⁷ and 10¹⁹cm^–3. Temperatures employed ranged fromT=2 to 77 K and magnetic fields were applied up toB=22 T. Supplementing Kane's theory by introducing both temperature and electron concentration dependence, the nonparabolicity of the effective mass for temperatures betweenT=0 K and 300 K is calculated. The result fits quite well to the experimental results.Dedicated to Prof. Dr. Günter Lautz on the occasion of his 70th birthday     

The effect of Zeeman splitting on Shubnikov-de Haas oscillations in two-dimensional systems

A theory of the Shubnikov-de Haas effect is developed for two-dimensional systems in a tilted magnetic field. The conductivity tensor is calculated for an arbitrary ratio r of the Zeeman splitting to the cyclotron splitting. Possible anisotropy of the g factor is taken into account. It is shown that at integer values of r, the main harmonic dominates in the spectrum of Shubnikov-de Haas oscillations and the phase of the oscillations depends on the parity of r. At half-integer values of r, the conductivity oscillations are determined by the harmonics of the second order of smallness.     

Shubnikov-de Haas effect in the metallic state of Na0.3CoO2

Shubnikov-de Haas oscillations for two well-defined frequencies, corresponding, respectively, to areas of 0.8 and 1.36% of the first Brillouin zone, were observed in single crystals of Na(0.3)CoO2. The existence of Na superstructures in Na0.3CoO2, coupled with this observation, suggests the possibility that the periods are due to the reconstruction of the large Fermi surface around the Gamma point. An alternative interpretation in terms of the long sought-after epsilon'(g) pockets is also considered but found to be incompatible with existing specific heat data.     

Observation of Shubnikov-de Haas Oscillations in Large-Scale Weyl Semimetai WTe2 Films

Topological Weyl semimetal WTe2 with large-scale Him form has a promising prospect for new-generation spintronic devices.However,it remains a hard task to suppress the defect states in large-scale WTe2 films due to the chemical nature.Here we significantly improve the crystalline quality and remove the Te vacancies in WTe2 films by post annealing.We observe the distinct Shubnikov-de Haas quantum oscillations in WTe2 films.The nontrivial Berry phase can be revealed by Landau fan diagram analysis.The Hall mobility of WTe2 films can reach 1245cm^2V^-1s^-1 and 1423cm^2V^-1s^-1 for holes and electrons with the carrier density of 5× 10^19 cm^-3 and 2 × 10^19 cm^-3,respectively.Our work provides a feasible route to obtain high-quality Weyl semimetal films for the future topological quantum device applications.     

Shubnikov-de Haas effect of n-inversion layers in InSb grain boundaries

Hall effect and Shubnikov-de Haas effect have been investigated in a n-inversion layer adjacent to the grain boundary in p-InSb bicrystals. The observed quantum oscillations of the magnetoconductivity result from a superposition of the Shubnikov-de Haas effect in two occupied subbands. The electron densities of the subbands n_si(n_s1=3.5 × 10¹¹cm^-2;n_s0= 1.1 × 10¹²cm^-2) and the effective cyclotron mass of the lower subband m_c0=(0.023 ± 0.002)m₀ have been evaluated.     

Shubnikov-de Haas effect and semimetal-semiconductor transition in bismuth-antimony alloys in high magnetic fields

Shubnikov-de Haas effect is observed in Bi and BiSb alloys (containing 0.1?4.4 at.% Sb) in pulsed high magnetic fields up to 420 kG. It is found that the amplitude of the quantum oscillation remarkably increases by mixing a small amount of Sb in Bi, and that the magnitude of the Hall electric field in BiSb alloy (0.1 at.% Sb) is much larger than that in pure Bi. These observations demonstrate the difference in the scattering mechanism of carriers between Bi and BiSb alloys. The magnetic field induced semimetal to semiconductor transition is observed in BiSb alloy with 4.4 at.% Sb. From the analysis of the Shubnikov-de Haas oscillation in BiSb, the field at which the semimetal to semiconductor transition will occur in Bi is estimated as about 1 MG for the field direction parallel to the binary axis.     

Observation of Shubnikov-de Haas Oscillations in Large-Scale Weyl Semimetal WTe_2 Films

Topological Weyl semimetal WTe_2 with large-scale film form has a promising prospect for new-generation spintronic devices.However,it remains a hard task to suppress the defect states in large-scale WTe_2 films due to the chemical nature.Here we significantly improve the crystalline quality and remove the Te vacancies in WTe_2 films by post annealing.We observe the distinct Shubnikov-de Haas quantum oscillations in WTe_2 films.The nontrivial Berry phase can be revealed by Landau fan diagram anal.ysis.The Hall mobility of WTe_2 films can reach 1245 cm~2 V~(-1)s~(-1) and 1423 cm~2 V~(-1)s~(-1) for holes and electrons with the carrier density of 5×10~(19) cm~(-3) and2×10~(19) cm~(-3),respectively.Our work provides a feasible route to obtain high-quality Weyl semimetal films for the future topological quantum device applications.     

Dependence of the ferromagnetic-resonance parameters of polycrystalline ferrites on uniaxial elastic stress

Methods developed for taking into account the effect of magnetic crystallographic anisotropy on ferromagnetic resonance in polycrystalline ferrites are used to calculate the dependence of the line width of resonant ferromagnetic absorption and the magnitude of the resonant field of polycrystalline ferrites on uniaxial elastic stress.Translated from Izvestiya Vysshikh Uchetanykh Zavedenii Fizika, No. 10, pp. 49–55, October, 1970.     

Shubnikov-de Haas oscillations of massive Dirac fermions in a Dirac antiferromagnet SrMnSb2

We investigate the physical properties of massive Dirac fermions in SrMnSb₂ using transport, specific heat, electronic structure calculations, and Shubnikov-de Haas (SdH) oscillations. SrMnSb₂ is a candidate Dirac antiferromagnet, consisting of the MnSb layers and the distorted square net of Sb atoms with a zigzag chain structure. This structural distortion leads to gap opening at the band crossing point found in the square lattice of the sister compound SrMnBi₂ but leaves another Dirac band crossing near the Brillouin zone boundary. The small 2D Fermi surface with a light electron mass and a small Fermi energy is confirmed by the large resistivity anisotropy, the large Seebeck coefficient, and also the angle and temperature dependent SdH oscillations. The Berry phase obtained from the SdH oscillations is trivial, in contrast to the case of SrMnBi₂. The relatively large spin orbit coupling gap and the small Fermi energy in SrMnSb₂ is found to be essential to understand this contrasting behavior of the massive Dirac fermions as compared to SrMnBi₂. Our observations demonstrate that the Berry phase of the mobile electrons in SrMnSb₂ is sensitive to the Fermi level change and can be tuned by doping or deficiency.     

Beatings of Shubnikov-de Haas oscillations in a two-dimensional hole system in an InGaAs quantum well

The magnetoresistance of an InGaAs/GaAs heterostructure with a two-dimensional hole channel has been measured in quantizing magnetic fields. Beatings of Shubnikov-de Haas oscillations have been observed, which indicate that the spin degeneracy of the system is lifted owing to the spin-orbit interaction. The oscillation pattern is independent of the magnetic field component parallel to the two-dimensional system; this independence is characteristic of size-quantization heavy-hole subbands.     

Shubnikov-de Haas oscillations and the magnetic-field-induced suppression of the charge ordered state in Na(0.5)CoO2

We have performed electrical transport measurements at low temperatures and high magnetic fields in Na(0.5)CoO2 single crystals. Shubnikov-de Haas oscillations corresponding to only 1% of the area of the orthorhombic Brillouin zone were clearly observed, indicating that most of the original Fermi surface vanishes at the charge-ordering (CO) transition. In-plane magnetic fields were found to suppress strongly the CO state. For fields rotated within the conducting planes, we observe angular magnetoresistance oscillations whose periodicity changes from twofold to sixfold at the transition.     

Galvanomagnetic effects in graphite—III: The effect of neutron irradiation on the quantum limit Shubnikov-de Haas oscillations

Galvanomagnetic effects have been studied for a range of highly oriented, neutron-irradiated samples of graphite at 1.2–7K, in fields up to 9 Tesla. Irradiation doses were in the range $\text{0}\text{?}\text{?3× 10}{}^{17}\text{nvt}\text{(E> 1}\text{MeV}$). Asymptotic values of σ_xyB were used to obtain independent values of the carrier density difference (P-N). Shubnikov-de Haas frequencies, effective masses, Dingle temperatures and coincidence fields in the quantum limit were measured. Theoretical values for the variation of these quantities with the Fermi energy, (P-N) and with band overlap parameters were also obtained. The results could not be fitted to a simple model in which reasonable changes were allowed in ?_F and the band parameters.