Spin Polarization Phenomena and Pseudospin Quantum Hall Ferromagnetism in the HgTe Quantum Well

The parallel field of a full spin polarization of the electron gas in a \Gamma8 conduction band of the HgTe quantum well was obtained from the magnetoresistance by three different ways in a zero and quasi-classical range of perpendicular field component Bper. In the quantum Hall range of Bper the spin polarization manifests in anticrossings of magnetic levels, which were found to strongly nonmonotonously depend on Bper.Comment: to be published in AIP Conf. Proc.: 15-th International Conference on Narrow Gap Systems (NGS-15

Effect of the Magnetic Prehistory on the Low-Temperature Heat Capacity of the La(Fe0.88Al0.12-xSix)13 Compounds

The measured heat capacity C of solids is thought in general to involve the change of the internal energy which is a state property. Therefore the electron density of states at the Fermi level is derived from the low-temperature data C=γ T + β T3. The La(Fe0.88Al 0.12-xSix)13 compounds are the antiferromagnets (AFM) TN=200 K with 0<x<0.03 and the ferromagnets (FM) with 0.03<x<0.12 TC=194 K. For x=0.024 and x=0.027 a metamagnetic phase transition from AFM to the field-induced FM (FIFM) occurs in low external magnetic field. The FIFM state of the sample remains if the magnetic field turns off. The measurements of the low-temperature heat capacity in this FIFM state have shown an increase of coefficient γ in comparison with the value both the AFM and the FM. The measured heat capacity depends on a thermodynamic path and thus is not a state property. The change of the work of the magnetostrictive strain of the sample as a part of the low-temperature heat capacity is discussed. © 2010 IOP Publishing Ltd

Temperature dependence of quantum lifetime in n-InGaAs/GaAs structures with strongly coupled double quantum wells

Longitudinal ρxx(B) and Hall ρxy(B) magnetoresistances are experimentally investigated as a function of in-plane and transverse magnetic fields in n-InGaAs/GaAs nanostructures with strongly-coupled double quantum wells in the temperature range T = 1.8-70 K and magnetic fields B = 0-9.0 T. Experimental data on the temperature dependence of quantum lifetime in diffusive (kBT/τtr ≪ 1) and ballistic (kBT/τtr ≫ 1) regimes are reported. It has been found that in the ballistic regime in the temperature range where kBT/EF < 0.1, the observed quadratic temperature dependence of quantum lifetime is determined by inelastic electron-electron scattering. However, the temperature dependence of quantum lifetime cannot be quantitatively described by the existing theories in the whole temperature range. © 2013 American Institute of Physics

Effects of spin polarization in the HgTe quantum well

Magnetoresistivity features connected with the spin level coincidences under tilted fields in a Γ 8 conduction band of the HgTe quantum well were found to align along straight trajectories in a (B ⊥,B) plane between the field components perpendicular and parallel to the layer, meaning a linear spin polarization dependence on a magnetic field. Among the trajectories is a noticeable set of lines descending from a single point on the Baxis, which is shown to yield a field of the full spin polarization of the electronic system, in agreement with the data on the electron redistribution between spin subbands obtained from Fourier transforms of oscillations along circle trajectories in the (B ⊥,B) plane and with the point on the magnetoresistivity under pure Bseparating a complicated weak field dependence from the monotonous one. The whole picture of coincidences is well described by the isotropic g factor, although its value is twice as small as that obtained from oscillations under pure perpendicular fields. The discrepancy is attributed to different manifestations of spin polarization phenomena in the coincidences and within the exchange-enhanced spin gaps. In the quantum Hall range of B ⊥, the spin polarization manifests in anticrossings of magnetic levels, which were found to depend dramatically nonmonotonously on B ⊥. © 2012 American Physical Society

Tunneling effects in tilted magnetic fields in n-InGaAs/GaAs structures with strongly coupled double quantum wells

The effects of tunneling between two parallel two-dimensional electron gases in n-InGaAs/GaAs nanostructures with strongly coupled double quantum wells with a change in the in-plane component of a tilted magnetic field (up to Bnorm of matrix = 9.0 T) in the temperature range T = 1.8-70.0 K are investigated. A nonmonotonic temperature dependence of the inverse quantum lifetime τq -(T) is obtained from analysis of the dependence of the longitudinal resistance on the parallel component of the tilted magnetic field at fixed temperatures, ρxx(Bnorm of matrix, T). The quadratic portion of this dependence is found to be due to the contribution of inelastic electron-electron scattering. The decrease in the inverse quantum lifetime τq -(T) at T &gt; 0.1T F cannot be described within known theories; it seems, it is not related to the processes of electron momentum relaxation. © 2013 Pleiades Publishing, Ltd

Spin Polarization Phenomena and Pseudospin Quantum Hall Ferromagnetism in the HgTe Quantum Well

The parallel field of a full spin polarization of the electron gas in a Γ 8 conduction band of the HgTe quantum well was obtained from the magnetoresistance by three different ways in a zero and quasi-classical range of perpendicular field component B⊥. In the quantum Hall range of B⊥ the spin polarization manifests in anticrossings of magnetic levels, which were found to strongly nonmonotonously depend on B⊥. © 2011 American Institute of Physics.Authors are grateful to E. Palm, T. Murphy, J. H. Park, and G. Jones for help with the experiment. Supported by RFBR, pr ojects 11-02-00427, 09-02-96518. NHMFL is supported by NSF (DMR-0654118), the State of Florida, and the US DOE

Electronic transport features of MoTe2caused by quenching

The electro- and magnetoresistivity of MoTe2 single crystals before and after quenching were measured at temperatures from 1.8 to 300 K and in magnetic fields of up to 9 T. It was demonstrated that quenching can lead to strong changes in values of the electro-and magneresistivity studied as well as in their temperature and field dependences. The peculiarities of these electronic transport characteristics changes were studied in detail. © Published under licence by IOP Publishing Ltd.The research was carried out within the state assignment of the Ministry of Education and Science of the Russian Federation (theme “Spin”, No. АААА-А18-118020290104-2), supported in part by RFBR (Project No. 17-52-52008) and the Government of Russian Federation (Decree No. 211, Contract No. 02.A03.21.0006)