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An array of embedded graphene ribbons, whose edges connect to a buffer layer, can be grown on 4HSiC(0001). The Raman D peak intensity of the armchair edge of the ribbon shows the same polarization dependence as that of the non-connected armchair edge of graphene. Considering the Raman scattering process of the D peak, this polarization dependence indicates that electrons and holes in the embedded graphene by incident photons are scattered back at the boundary of the embedded graphene ribbon and buffer layer. These results indicate polarized Raman scattering spectroscopy is useful for investigating the edge structure of embedded graphene.

In transition metal dichalcogenide (TMDC) heterostructures, interlayer coupling plays a crucial role in the design and emergence of diverse properties. Here, we show the control of the interlayer coupling in Janus WSSe/WS2 heterostructures by changing the stacking order. Low-frequency Raman measurements revealed that heterostructures with the S/S interface show strong interlayer coupling compared to those with the S/Se interface. In the case of the S/S interface, photoluminescence (PL) from WS2 was quenched due to charge transfer in the type-II band alignment, while, interestingly, in the case of the S/Se interface, it was enhanced. The stacking-order dependence of the interlayer coupling and photoluminescence are attributed to the direction of interfacial electric field caused by broken out-of-plane mirror symmetry in a WSSe layer. In the case of the S/S interface, the interfacial electric field promotes the charge transfer as evidenced by strong PL quenching. On the contrary, in heterostructures with the S/Se interface, the charge transfer is blocked as the electric field prevents carrier transfer and modulates the band offset. Our results clearly show that Janus TMDCs with intrinsic fields can be effectively used to manipulate the interlayer interactions and optical properties in heterostructures.

We report the growth of aluminum (111) thin film by atomic layer deposition (ALD) technique with dimethylethylaminealane (DMEAA) as a precursor. It is found that the metallic underlayer is essential to grow uniform aluminum films by DMEAA precursor. As a titanium thin film is used as the underlayer, grown aluminum thin film shows (111) orientation irrespective of substrates. The lattice constant and superconducting transition temperature of the aluminum thin films are the same as the bulk one. These findings suggest that ALD technique provides high quality of the aluminum thin films and have potential for the applications of superconducting devices. We discuss ALD technique with DMEAA precursor is the promising method for fabricating vertical small Josephson tunnel junctions, which can be used as the superconducting quantum bits., Comment: 13 pages, 3 figures, Accepted manuscript

Dynamical energy and momentum mapping for intervalley electron transfer in WSe2 was investigated with high-harmonic-based ultrafast ARPES. The measured ultrashort scattering time of 30 fs will provide a guide to lightwave control of valley pseudospin.

We investigate the coupling between quantum Hall (QH) edge channels (ECs) located at opposite sides of a 50-μm-wide Hall bar by exciting a charged wavepacket in one EC and detecting time-dependent current in the other EC. In a QH state, the current shows a peak followed by a dip, demonstrating the existence of capacitive coupling across the incompressible two-dimensional electron system (2DES). The observed magnetic field dependence of the amplitude and time delay of the current suggests that the capacitance is affected by the presence of localized states. We also show that the dominant manner of the coupling changes gradually as the system changes between the QH and non-QH states.

We report an approach for examining electron properties using information about the shape and size of a nanostructure as a measurement reference. This approach quantifies the spin precession angles per unit length directly by considering the time-reversal interferences on chaotic return trajectories within mesoscopic ring arrays (MRAs). Experimentally, we fabricated MRAs using nanolithography in InGaAs quantum wells which had a gate-controllable spin-orbit interaction (SOI). As a result, we observed an Onsager symmetry related to relativistic magnetic fields, which provided us with indispensable information for the semiclassical billiard ball simulation. Our simulations, developed based on the real-space formalism of the weak localization/antilocalization effect including the degree of freedom for electronic spin, reproduced the experimental magnetoconductivity (MC) curves with high fidelity. The values of five distinct electron parameters (Fermi wavelength, spin precession angles per unit length for two different SOIs, impurity scattering length, and phase coherence length) were thereby extracted from a single MC curve. The methodology developed here is applicable to wide ranges of nanomaterials and devices, providing a diagnostic tool for exotic properties of two-dimensional electron systems.

We demonstrate time-resolved ARPES based on the 27th harmonic pulse with sub-10-fs duration. The measurement for the initial stage of carrier photoexcitation near the Dirac point of graphite confirms duration of 8 fs.

We investigate charge fractionalizations in artificial Tomonaga-Luttinger liquids (TLLs) composed of two capacitively coupled quantum Hall edge channels (ECs) in graphene. The interaction strength of the artificial TLLs can be controlled through distance W between the ECs. We show that the fractionalization ratio r and the TLL mode velocity v vary with W. The experimentally obtained relation between v and r follows a unique function predicted by the TLL theory. We also show that charged wavepackets are reflected back and forth multiple times at both ends of the TLL region., to be published in Phys. Rev. B Rapid Communication

A thorough understanding of the stability of graphene under ambient environmental conditions is essential for future graphene-based applications. In this paper, we study the effects of ambient temperature on the properties of monolayer graphene using terahertz time-domain spectroscopy as well as time-resolved terahertz spectroscopy enabled by an optical-pump/terahertz-probe technique. The observations show that graphene is extremely sensitive to the ambient environmental conditions and behaves differently depending on the sample preparation technique and the initial Fermi level. The analysis of the spectroscopic data is supported by van der Pauw and Hall effect measurements of the carrier mobility and carrier density at temperatures comparable to those tested in our THz spectroscopic experiments.

We report thermal effects on carrier dynamics in graphene revealed by terahertz spectroscopy. We attribute our observations to extreme sensitivity of carrier density and mobility to environmental changes.

We report a novel etchant-free transfer method of graphene using the intercalation of alkanethiol self-assembled monolayers (SAMs) at the graphene/Cu interfaces. The early stage of intercalation proceeds through graphene grain boundaries or defects within a few seconds at room temperature until stable SAMs are formed after a few hours. The formation of SAMs releases the compressive strain of graphene induced by Cu substrates and make graphene slightly n-doped due to the formation of interface dipoles of the SAMs on metal surfaces. After SAM formation, the graphene is easily delaminated off from the metal substrates and transferred onto insulating substrates. The etchant-free process enables us to decrease the density of charged impurities and the magnitude of potential fluctuation in the transferred graphene, which suppress scattering of carriers. We also demonstrate the removal of alkanethiol SAMs and reuse the substrate. This method will dramatically reduce the cost of graphene transfer, which will benefit industrial applications such as of graphene transparent electrodes.

We recently determined the values of intrinsic spin-orbit (SO) parameters for In 0.52 Al 0.48 As/In 0.53 Ga 0.47 As(10 nm)/In 0.52 Al 0.48 As (InGaAs/InAlAs) quantum wells (QW), lattice-matched to (001) InP, from the weak localization/antilocalization analysis of the low-temperature magneto-conductivity measurements [1]. We have then studied the subband energy spectra for the InGaAs/InAlAs double QW system from beatings in the Shubnikov de Haas (SdH) oscillations. The basic properties obtained here for the double QW system provides useful information for realizing nonmagnetic spin-filter devices based on the spin-orbit interaction [2]. Copyright © 2012 The Institute of Electronics, Information and Communication Engineers.

We report the experimental detection of the anisotropic spin–orbit interaction (SOI) in InGaAs/InAlAs quantum wells, using spin interference experiments in arrays of rectangular loops with their sides aligned to the [1 1 0] and [ 1 1 ¯ 0 ] crystallographic directions. While the gate voltage is tuned, the time reversal Aharonov–Casher (TRAC) oscillations exhibit higher frequencies when the loops have their longer side along the [1 1 0] direction, clearly highlighting the anisotropy of the SOI. We find that a simple spin interferometer model, including both the Rashba and the Dresselhaus SOIs, reproduces qualitatively the TRAC oscillations.

We report an unambiguous detection of the crytalline anisotropy of the spin-orbit interaction in (001) InAlAs/InGaAs/InAlAs quantum wells using nanofabricated rectangular loop arrays, where the sides of the constituent loops are aligned along either the [110] or [ 1 1 0 ] crystallographic axis. The fabrication and measurements were performed on the epi-wafer samples whose spin properties were characterized previously [Koga et al. Phys. Rev. Lett 89 (2002) 046801]. We find that the experimentally observed spin interference patterns — the amplitude modulation of the Al’tshuler–Aronov–Spivak oscillations as a function of the gate voltage — are in good agreement with the results of the spin interferometer model extended for rectangular loops and including both the Rashba and Dresselhaus spin-orbit interactions.

We have observed the well-kown quantum Hall effect (QHE) in epitaxial graphene grown on silicon carbide (SiC) by using, for the first time, only commercial NdFeB permanent magnets at low temperature. The relatively large and homogeneous magnetic field generated by the magnets, together with the high quality of the epitaxial graphene films, enables the formation of well-developed quantum Hall states at Landau level filling factors $\nu=\pm 2$, commonly observed with superconducting electro-magnets. Furthermore, the chirality of the QHE edge channels can be changed by a top gate. These results demonstrate that basic QHE physics are experimentally accessible in graphene for a fraction of the price of conventional setups using superconducting magnets, which greatly increases the potential of the QHE in graphene for research and applications., Comment: 9 pages, 3 figures

We propose a lateral spin-blockade device that uses the interband Rashba effect in a symmetric double quantum well (QW), where the Rashba effect in the conventional sense vanishes because of its inversion symmetry. The interband Rashba effect manifests itself in the off-diagonal term (represented by the parameter eta) in the QW space using the bonding and antibonding basis [Esmerindo Bernardes, John Schliemann, Minchul Lee, J. Carlos Egues, and Daniel Loss, Phys. Rev. Lett. 99, 076603 (2007)]. In such a system, spin selection is possible by tuning the device length, gate electric field and in-plane magnetic field. We particularly show illustrative mechanisms using a one-dimensional model with k = (k(F), 0), where the selected spin can be blocked completely in the presence of the in-plane magnetic field. While the inclusion of the finite k(y) and/or the gate electric field deteriorates the spin polarization P, finite values remain for P (P>11%). Our proposal can also be regarded as an effective way of enhancing a variation of the Rashba-Edelstein effect, the generation of bulk spin polarization by electric current, based on semiconductor band engineering technology.

Recently, spin interference effect based on the Rashba effect in a square loop (SL) geometry is proposed theoretically [Koga et al., Phys. Rev. B 70, 161302(R) (2004)] and demonstrated experimentally [Koga et al., Phys. Rev. B 74 in press] using In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As quantum wells (QW), where the spin precession angle θ per side of the SL can be controlled by the applied gate voltage via the Rashba spin-orbit coupling constant α. In the present work, we include the effect of the bulk inversion asymmetry, so-called Dresselhaus term, in our model calculation. We found that the agreement between the experimental and simulation results are greatly improved by the inclusion of the Dresselhaus term in the model calculation. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report etching-free and iodine-free transfer of highly aligned array of armchair-edge graphene nanoribbons (ACGNRs) and their field-effect transistor (FET) characteristics. They were prepared by on-surface polymerization on Au(788) templates. The ACGNRs were mechanically delaminated and transferred onto insulating substrates with the aid of a nano-porous support layer composed of hydrogen silsesquioxane (HSQ). The key process in the mechanical delamination is the intercalation of octanethiol self-assembled monolayers (SAMs), which penetrate the HSQ layer and intercalate between the ACGNRs and Au(788). After the transfer, the octanethiol SAMs were removed with Piranha solution, enabling the reuse of the Au single crystals. The FETs fabricated with the transferred ACGNR array showed ambipolar behavior when the channel length was as long as 60 nm. Quasi-one-dimensional conductivity was observed, which implies a good alignment of GNRs after the transfer. In contrast, short-channel ACGNR FETs (channel length ∼20 nm) suffer from a geometry-dependent short-channel effect. This effect is more severe in the FETs with ACGNRs parallel to the channel, which is an ideal geometry, than in ones perpendicular to the channel. Since the ID-VD curve is well fitted by the power-law model, the short-channel effect likely stems from the space-charge limited current effect, while the wide charge-transfer region in the GNR channel can be another possible cause for the short-channel effect. These results provide us with important insights into the designing short-channel GNR-FETs with improved performance.

Optical measurements on highly doped single-layer epitaxial graphene reveal that the photoexcitation of charge carriers leads to an enhancement of the THz transmission. In this paper, the results are explained in terms of the change in the carrier scattering rate due to the optical pump fluence and the THz electric field.

Polarized transmission and reflection spectra in the terahertz region were obtained from a graphene complementary split ring resonator device. The complementary structure combined with an ion gel gate electrode rendered the optical properties of the device tuneable. The oscillator strength at the intraband plasmon resonance was largely enhanced with the gate-voltage-induced doping, and absorption exceeded 2.3%/layer of the interband transition. The resonance frequency could also be largely increased with the gate voltage. These results suggest the possibility of graphene-based metamaterials with tuneable permeability or permittivity and tuneable resonance frequencies.

We developed a method of precise measurement of the dielectric constant under multi-extreme conditions, that is, under high pressures, high magnetic fields and low temperatures. We measured the dielectric constants and the magnetic susceptibility of single crystals of α ′ -NaV 2 O 5 under multi-extreme conditions. Anisotropic behavior of a relative dielectric constant was observed at the charge-ordering transition temperature under ambient pressure. With increasing hydrostatic pressure, the transition temperature decreased and another transition appeared below the first transition temperature. The susceptibility exhibited a sharp drop corresponding to the transition to the spin singlet state at the first transition temperature, while it showed no anomaly at the second transition temperature. These two transition temperatures were found to exhibit very weak magnetic field dependence in comparison with typical spin-Peierls compounds.

The bandwidth-controlled metal-insulator (MI) transition in pyrite-type NiS 2- x Se x has been investigated. The results indicate that the approach to the MI transition from the metallic side is pr...

Transport, thermal and elastic properties under the hydrostatic pressure p up to 21.2 kbar have been studied on the layered compound BaCoS 2 , which exhibits the Mott insulator→metal transition wit...

Yb4As3 shows anomalous transport phenomena below the phase-transition temperature associated with an order-disorder transition due to the atomic arrangement between Yb3+ and Yb2+. Although the LIII spectrum shows no change in valence above and below the temperature, the large increase of the trivalent component has been clearly observed with increasing pressure. Comparing the pressure- and temperature-dependent resistivity between Yb4As3 and Yb4Sb3, it is suggested that the anomalous transport properties of Yb4As3 are due to a characteristic electronic structure modulated with the phase transition.

ently, many studies on the application of Er: YAG laser in the dental field have been reported. Er: YAG laser can ablate dental hard tissues with small thermal damages, and is clinically applied for removal of dental caries. However, there are few studies on apicoectomy using Er: YAG laser. The purpose of this study was to compare apicoectomy using Er: YAG laser and the conventional cutting method in vitro.Extracted single-rooted human teeth were used in this experiment. Root resection was performed with Er: YAG laser (output energy: 70mJ10pps) or a fissure bur mounted to a micro-motor. Resected root surfaces were evaluated with scanning electron microscopy.In addition, cutting efficiency of both methods and dye penetration of the cut surface were compared. After removing the tooth crown of 10 extracted single-rooted human teeth, root canals were cleaned, shaped and obturated. Then, the samples were randomly divided into two groups. Root resection by Er: YAG laser or micro-motor was perfOrtned, and working time was counted and the cut surface area measured. Then, all the root surfaces were sealed with nail polish except the resected surface. All roots were placed into 0.1% methylene blue dye for 7 days, rinsed and air-dried. Finally, they were split and the dye penetration from the resected surface was measured and statistically analyzed.The results were as follows:1. There were no smear layer or debris left on the resected surface cut by Er: YAG laser, and the shape of the cut surface was irregular. On the other hand, both smear layer and debris were observed on the surface cut by the conventional method, and the cut surface was smooth.2. The cutting efficiency of Er: YAG laser and micro-motor was 14.8 (±7.3) sec./mm2 and 4.4 (±1.7) sec./ram2, respectively. Cutting by Er: YAG laser significantly needed more time than that by micro-motor (t-test, P

Raman spectroscopy has been used in chemistry and physics to investigate the fundamental process involving light and phonons (quantum of lattice vibration). The carbon nanohorn introduces a new subject to Raman spectroscopy, namely topology. We show theoretically that a photo-excited carrier with a non-zero winding number activates a topological $D$ Raman band through the Aharonov-Bohm effect. The topology-induced $D$ Raman band can be distinguished from the ordinary $D$ Raman band for a graphene edge by its peak position., 12 pages, 3 figures

The aim of this study was to histopathologically investigate the effects of pulsed Nd: YAG laser irradiation on the periradicular tissues when applied in the root canal of the dog.Six adult mongrel dogs were anesthetized and the tooth pulps of the upper and lower premolars were extirpated. Each root canal was cleaned and shaped to a final apical file size #55. Non-irradiated root canals were served as control.The laser irradiation (100mJl0pps, 100mJ20pps, 100mJ30pps, 200mJ10pps and 200mJ20pps) was performed under an up-and-down motion in the root canal between the apical and cervical portion with an optical fiber (∅=400μm) for 30 sec. After the irradiation, a small cotton pellet soaked with formalin cresol was placed in the pulp chamber and the access cavity was filled with glass ionomer cement. The animals were sacrificed at 7 and 28 days postoperatively.The results were as follows:1. At 7 days postoperatively, no histopathological difference was found between the control and 100mJ10pps group. On the other hand, carbonization and defects of the root canal wall were observed in all laser-treated groups except the 100mJ10pps group.2. At 28 days postoperatively, alveolar bone resorption was often observed again in all laser-treated groups except the 100mJ10pps group. Furthermore, in the 100mJ20pps group, dentoalveolar ankylosis was observed in the periradicular tissues, and severe external root resorption was frequently seen in the 200mJ20pps group. However, in the 100mJ10pps group, the degree of inflammation in the periradicular tissues was similar to the control.3. It was concluded that pulsed Nd: YAG laser with irradiation energy less than 100mJ10pps could be used safely in the root canal of the dog.(J. Jpn. Soc. Laser Dent. 7: 12-21, 1996 Reprint requests to Dr. SEKINE)

We have fabricated a planar cold cathode based on a multilayer (ML)-graphene/SiO2/Si heterostructure. When voltage is applied between the ML graphene and Si layer, electrons tunnel from the Si layer to the ML-graphene through the SiO2. During this tunneling event, electrons repeatedly gain and lose energy in the SiO2 owing to the electric field and scattering, respectively. Electrons whose energy is larger than the work function of the ML-graphene are emitted from its surface to a vacuum. The thinness of the ML-graphene reduces the energy loss of electrons in it and thus improves electron emission characteristics.

We evaluate the degree of disorder in electrolyte-gating devices through transport measurements in graphene. By comparing the mobility in ion- and standard metal-gated devices, we show that the deposition of the ionic liquid introduces charged impurities that limit the mobility in graphene to 3 × 103 cm2 V−1 s−1. At higher temperatures (>50 K), phonons in the ionic liquid further reduce the mobility, making its upper limit 2 × 103 cm2 V−1 s−1 at room temperature. Since the degree of disorder is independent of the base material, these results are valuable for understanding disorder effects in general devices using electrolyte gating.

The purpose of this study was to investigate the effect of Nd: YAG laser irradiation on Streptococcus mutans.Roots of intact bovine incisors were used in this experiment. After cleaning and shaping of the root canal, they were acid-etched for 1 minute and ultrasonically irrigated. The root surface was coated with nail enamel and the samples were sterilized. Each root canal was filled with 50μl of culture medium where S. mutans was incubated at 37°C for 24 hours. One hundred roots were divided into 10 groups according to irradiation energy and addition of evans blue in the culture medium. Non-irradiated samples were used as control.The culture medium in the root canal was irradiated under up-and-down motion between the apical and cervical portion of the root canal with an optical fiber (∅=600, μm) for 30 seconds using Nd: YAG laser (100mJ or 200mJ and 10 or 30 pps). After the irradiation, bacterial samples of 10μl were taken from each root canal and incubated aerobically on Mitis Salivalius Agar at 37°C for 72 hours. The number of colonies on the medium was counted and colony-forming-units (CFUs) /ml were calculated.Thermal change caused by Nd: YAG laser irradiation in the root canal and culture medium was also monitored with a thermal camera. In addition, the irradiated dentin surface of the canal wall was observed with SEM.The results were as follows:1. In comparison with the control group, the CFUs in 100mJ 10pps, 200mJ 10pps, 100mJ 30pps and 200mJ 30pps irradiated groups without evans blue were reduced to 41%, 37%, 16% and 2%, respectively. Likewise, the CFUs in 100mJ 10pps, 200mJ 10pps, 100mJ 30pps and 200mJ 30pps irradiated groups with evans blue were reduced to 46%, 34%, 3% and 0%, respectively. The bactericidal effect in all experimental groups was statistically significant compared with the control group (t-test, P

We present a semiclassical interpretation of the time-reversal spin interference (SI) observed in the square loop arrays made of In 0.53 Ga 0.47 As quantum wells. The simulated amplitude of SI as a function of the Rashba parameter α captured characteristic features in the experimental results if γ8 eV3 is assumed for the bulk Dresselhaus spin-orbit constant γ. Our work proves the validity of the semiclassical approach to predict the effect of time-reversal quantum interference in mesoscopic systems and the values of the spin-orbit coefficients recently deduced from the weak localization/antilocalization experiment. © 2011 American Physical Society.

Carrier density and temperature-dependent transport properties of monolayer graphene grown on SiC(0001) were systematically studied. With increasing temperature, resistivity at the charge neutrality point decreases, while resistivity away from the charge neutrality point, where the carrier density is above 1 \ifmmode\times\else\texttimes\fi{} 10${}^{11}$ cm${}^{\ensuremath{-}2}$, increases. From Hall measurements and the temperature dependence of conductivity, carrier density at the charge neutrality point at 2 K is estimated to be 1 \ifmmode\times\else\texttimes\fi{} 10${}^{10}$ cm${}^{\ensuremath{-}2}$ or below. Such low carrier density implies a small potential fluctuation in graphene on SiC(0001). The carrier density at the charge neutrality point increases with increasing temperature and thus the resistivity decreases. At carrier densities away from the charge neutrality point, the mobility decreases with increasing temperature and the resistivity increases. We analyzed the decrease of mobility, assuming phonon scatterings that originate from the substrate.

We studied the electronic transport properties of monolayer and bilayer graphene in top-gated geometries. Monolayer and bilayer graphene were epitaxially grown by thermal decomposition of SiC. The half-integer quantum Hall effect under the gated environment was observed in monolayer graphene devices. The mobility of the monolayer and bilayer graphene devices showed distinct characteristics as a function of carrier density, which reflect their electronic structures. Strong temperature dependence at the charge neutrality point was observed in bilayer graphene devices, suggesting band gap opening.

We report the determination of the intrinsic spin‐orbit interaction (SOI) parameters and phase coherence times for In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As quantum wells (QWs) from the analysis of the weak antilocalization (WAL) measurements at dilution temperatures. We find that the Dresselhaus SOI is mostly negligible in this system and that the intrinsic parameters for the Rashba effect, aSO≡α/ is determined quantitatively to be aSOm*/me = (1.46–1.51×10−17NS[m−2])eA2, where NS is the sheet carrier density. We also provide the values of the phase coherent time τφ extracted from the WAL analysis and the transport mobility μ obtained from the Hall and Shubnikov‐de Haas (SdH) measurements.

Using the local Hall effect (LHE), we have succeeded in detecting a magnetic domain wall (DW) trapped in a permalloy Ni80Fe20 wire and in clearly distinguishing whether the DW structure is a head‐to‐head or a tail‐to‐tail DW. The LHE method has an advantage of large signal and makes it possible to investigate the inner DW structure.

A back-gate graphene p-n junction was achieved by selective interfacial modification of a chemical vapor deposition (CVD)-grown graphene field effect transistor (FET). Silane self-assembled monolayer (SAM) patterns were used to fabricate uniform p- and n-doped regions and a sharp p-n junction in the graphene FET channel. A gate-dependent photocurrent response was observed at the graphene p-n junction, and exhibited a maximum signal between two Dirac point voltages of SAM-doped graphene regions. A spatial photocurrent map shows that the photocurrent generated at the junction region was much larger than that from graphene/electrode junctions under the same incident laser power. This single-peak characteristic photocurrent in CVD graphene is dominated by the photothermoelectric contribution, and is highly sensitive to the power of incident laser. The SAM interfacial modification method provides a feasible route for the fabrication of efficient graphene-based photodetectors.

The transport properties of epitaxial graphene on SiC(0001) at quantizing magnetic fields are investigated. Devices patterned perpendicularly to SiC terraces clearly exhibit bilayer inclusions distributed along the substrate step edges. We show that the transport properties in the quantum Hall regime are heavily affected by the presence of bilayer inclusions, and observe a significant departure from the conventional quantum Hall characteristics. In particular, we observe anomalous values of the quantized resistance and a peculiar asymmetry with magnetic field which was not observed before for graphene on SiC. A quantitative model involving enhanced inter-channel scattering mediated by the presence of bilayer inclusions is presented that successfully explains the observed symmetry properties.

Resistivity and Hall effect measurements were made on single crystals of NiS2 and Ni(S0.9Se0.1)2 under high pressure in a temperature range between 4.2 and 300 K. NiS2 and Ni(S0.9Se0.1)2 show insulator-metal transitions. Anomalous behavior of resistivity corresponding to a para-antiferromagnetic transition was found in the metallic phase. The Hall coefficient and the Hall mobility decrease with increasing pressure. It is suggested that the electronic structure of Ni(S1−xSex)2 in the insulating phase is modified toward the phase boundary of the insulator-metal transition.

The Rashba spin-orbit interaction in InGaAs quantum wells (QW) is studied using the weak anti-localization analysis as a function of the structural inversion asymmetry (STA). A clear cross-over from positive to negative magnetoresistance near zero-magnetic field is observed by controlling the degree of the SIA in the QWs. This is a strong evidence of a zero-field spin splitting that is induced by the Rashba effect. The spin interference effect in a gate controlled mesoscopic loop structure is studied in the presence of the Rashba spin-orbit interaction. The oscillatory behaviors as a function of the gate voltage can be attributed to the spin interference effect. This result shows that the spin precession can be controlled by the gate voltage.