Transport properties of a 1000-nm HgTe film: the interplay of surface and bulk carriers

We report on systematic study of transport properties of a 1000-nm HgTe film. Unlike thinner and strained HgTe films, which are known as high-quality three-dimensional (3D) topological insulators, the film under study is much thicker than the limit of pseudomorphic growth of HgTe on a CdTe substrate. Therefore, it is expected to be fully relaxed and has the band structure of bulk HgTe, i.e., a zero gap semiconductor. Additionally, the system is characterized by the bands inversion, so that the two-dimensional (2D) topological surface states are expected to exist. To check this claim we studied classical and quantum transport response of the system. We demonstrate that by tuning the top-gate voltage one can change the electron-dominating transport to the hole one. The highest electron mobility is found to be more than 300 × 103 cm2/Vs. The system exhibits Shubnikov-de Haas (SdH) oscillations with a complicated pattern and shows up to 5 independent frequencies in corresponding Fourier spectra. They are attributed to the topological surface states, Volkov-Pankratov states and spin-degenerate bulk states in the accumulation layer near the gate. The observed peculiarities of the quantum transport are the strong SdH oscillations of the Hall resistance, and the suppressed oscillatory response of the topological surface states.

Probing Quantum Capacitance in a 3D Topological Insulator

We measure the quantum capacitance and probe thus directly the electronic density of states of the high mobility, Dirac type two-dimensional electron system, which forms on the surface of strained HgTe. Here we show that observed magnetocapacitance oscillations probe-in contrast to magnetotransport-primarily the top surface. Capacitance measurements constitute thus a powerful tool to probe only one topological surface and to reconstruct its Landau level spectrum for different positions of the Fermi energy.

Transport properties of a 3D topological insulator based on a strained high-mobility HgTe film

We investigate the magnetotransport properties of strained 80 nm thick HgTe layers featuring a high mobility of μ ∼ 4 × 10(5) cm(2)/V · s. By means of a top gate, the Fermi energy is tuned from the valence band through the Dirac-type surface states into the conduction band. Magnetotransport measurements allow us to disentangle the different contributions of conduction band electrons, holes, and Dirac electrons to the conductivity. The results are in line with previous claims that strained HgTe is a topological insulator with a bulk gap of ≈ 15 meV and gapless surface states.

[Effect of local anesthetics and phorbol ester on intracellular pH and rate of development of sea urchin embryos]

The unfertilized eggs of sand-dollars (Scaphechinus mirabilis) were treated with local anesthetics (novocaine, lidocaine, trimecaine) or phorbol ester for 10 min. The treatment with the local anesthetics increased pH of the cytoplasm in the unfertilized eggs (pHc) and changed the value of the pHc increment in response to fertilization, as compared with the control eggs. In the treated embryos, the onset of immigration of the primary mesenchyme cells was delayed but the hatching was accelerated. The phorbol ester treatment rapidly accelerated development from gastrulation on and practically did not affect the preceding stages.

[Concentration and distribution of insulin and insulin-like protein in the organs of normal and diabetic mice]

Presence of insulin or insulin-like protein has been studied in mouse liver, kidneys, lungs, duodenum, jejunum, submandibular and parotid salivary glands, in femoral, diaphragmal and abdominal wall muscles by means of the immunofluorescent method. In order to understand the role of the extrapancreatic insulin for compensation of the insular insufficiency, corresponding organs have been examined in mice with alloxan diabetes. The immunoreactive insulin is proved to be present only in cells of the granular parts of the salivary tubules of the submandibular and striated ducts of the parotid glands. As demonstrates microfluorometry, a relative amount of insulin in the submandibular gland cells is 1.5 times and in the parotid gland cells--2 times as small as in beta-cells of the pancreatic glands. Under alloxan diabetes insulin content in the salivary gland cells decreases by 1.3-1.9 times (in the beta-cells--by 2.7 times). This may designate that the extrapancreatic insulin (or insulin-like protein) participates in compensation of hypoinsulinemia. In mice with alloxan diabetes, immunoreactivity of insulin is also revealed in hepatocytes.

[Cytofluorimetric study of small, intensely fluorescing cells in the atria of rats following a single injection of guanethidine]

The fluorescence intensity of small high-fluorescent (SHF) cells of rat auricles was measured after the treatment by the modified Falk method in health and 3,14 and 72 hours after a single injection of guanethidine. No significant changes in the fluorescence intensity were found on analysis of the entire pool of SHF auricular cells and of individual SHF cells, while SHF cells of the clasters of the superior caval vein and interauricular septum manifest counterphasic deviations from the basal line of fluorescence, with these deviations being most remarkable 14 hours after the injection. The changes in the fluorescence intensity of SHF cells, which were seen within the periods of time corresponding with the minimum noradrenaline content in the heart allow the conclusion that SHF cell function is in good agreement with the heart noradrenaline level. The line of changes in the catecholamine content of SHF cells in the areas under consideration is likely to attest to the regional principle of the SHF cell pool organization in auricular tissue.