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Abstract: We examined the electron spin degree of freedom around the total Landau-level filling factor in a bilayer system via nuclear spins. In a balanced bilayer system, nuclear-spin-lattice relaxation rate , which probes low-energy electron spin fluctuations, increases gradually as the system is driven from the quantum Hall (QH) state through a phase transition to the compressible state. This result demonstrates that the electron spin degree of freedom is not frozen either in the QH or compressible states. Furthermore, as the density difference between the two layers is increased from balanced bilayer to monolayer configurations, around shows a rapid yet smooth increase. This suggests that pseudospin textures around the bilayer system evolves continuously into the spin texture for the monolayer system. [Copyright &y& Elsevier]

Throughout the body there are smooth muscle cells controlling a myriad of tubes and reservoirs. The cells show enormous diversity and complexity compounded by a plasticity that is critical in physiology and disease. Over the past quarter of a century we have seen that smooth muscle cells contain -- as part of a gamut of ion-handling mechanisms -- a family of cationic channels with significant permeability to calcium, potassium and sodium. Several of these channels are sensors of calcium store depletion, G-protein-coupled receptor activation, membrane stretch, intracellular Ca2+, pH, phospholipid signals and other factors. Progress in understanding the channels has, however, been hampered by a paucity of specific pharmacological agents and difficulty in identifying the underlying genes. In this review we summarize current knowledge of these smooth muscle cationic channels and evaluate the hypothesis that the underlying genes are homologues of Drosophila TRP (transient receptor potential). Direct evidence exists for roles of TRPC1, TRPC4/5, TRPC6, TRPV2, TRPP1 and TRPP2, and more are likely to be added soon. Some of these TRP proteins respond to a multiplicity of activation signals -- promiscuity of gating that could enable a variety of context-dependent functions. We would seem to be witnessing the first phase of the molecular delineation of these cationic channels, something that should prove a leap forward for strategies aimed at developing new selective pharmacological agents and understanding the activation mechanisms and functions of these channels in physiological systems. [ABSTRACT FROM AUTHOR]

Abstract Technical advancements in molecular genetics have shown various mitochondrial DNA (mtDNA) abnormalities in patients with mitochondrial myopathies. Recently, it has been revealed that, in these patients, the nuclear DNA carries sequences similar to those of the mtDNA (nuclear pseudogene) and it has several point mutations previously reported to be pathogenic. We verified the existence of the T3250C and T3291C mutations, which we have found in patients with mitochondrial myopathy, I [ABSTRACT FROM AUTHOR]

Examines the role of delayed rectifier K+ current (IK) in rabbit left atrium. Application of the whole cell voltage-clamp technique to isolated single myocytes; Contribution of IK with other K+ currents; Cell isolation; Electrical measurements; Identification of IK and sensitivity to E-4031.

K. Muraki, E. Ogo, H. Suefuji, H. Eto, C. Tsuji, C. Hattori, Y. Miyata, T. Abe, Poster: Physics track: Radiobiological and predictive modelling, and radiomics PO-1523: Predictive factors of over Grade 2 radiation pneumonitis for advanced non-small cell lung cancer. [Extracted from the article]

Examines the surface segregation of indium (In) atoms during molecular beam epitaxy. Influence of In surface segregation on the energy levels of indium gallium arsenide (InGaAs)/GaAS quantum wells; Dependence of In surface segregation on growth conditions; Effect of In desorption on In surface segregation.

Background: Chronic Fatigue Syndrome/ Myalgic Encephalomyelitis (CFS/ME) is a complex multifactorial disorder of unknown cause having multi-system manifestations. Although the aetiology of CFS/ME remains elusive, immunological dysfunction and more particularly reduced cytotoxic activity in natural killer (NK) cells is the most consistent laboratory finding. The Transient Receptor Potential (TRP) superfamily of cation channels play a pivotal role in the pathophysiology of immune diseases and are therefore potential therapeutic targets. We have previously identified single nucleotide polymorphisms in TRP genes in peripheral NK cells from CFS/ME patients. We have also described biochemical pathway changes and calcium signaling perturbations in NK cells from CFS/ME patients. Notably, we have previously reported a decrease of TRP cation channel subfamily melastatin member 3 (TRPM3) function in NK cells isolated from CFS/ME patients compared with healthy controls after modulation with pregnenolone sulfate and ononetin using a patch-clamp technique. In the present study, we aim to confirm the previous results describing an impaired TRPM3 activity in a new cohort of CFS/ME patients using a whole cell patch-clamp technique after modulation with reversible TRPM3 agonists, pregnenolone sulfate and nifedipine, and an effective TRPM3 antagonist, ononetin. Indeed, no formal research has commented on using pregnenolone sulfate or nifedipine to treat CFS/ME patients while there is evidence that clinicians prescribe calcium channel blockers to improve different symptoms. Methods: Whole-cell patch-clamp technique was used to measure TRPM3 activity in isolated NK cells from twelve age- and sex-matched healthy controls and CFS/ME patients, after activation with pregnenolone sulfate and nifedipine and inhibition with ononetin. Results: We confirmed a significant reduction in amplitude of TRPM3 currents after pregnenolone sulfate stimulation in isolated NK cells from another cohort of CFS/ME patients compared with healthy controls. The pregnenolone sulfate-evoked ionic currents through TRPM3 channels were again significantly modulated by ononetin in isolated NK cells from healthy controls compared with CFS/ME patients. In addition, we used nifedipine, another reversible TRPM3 agonist to support the previous findings and found similar results confirming a significant loss of the TRPM3 channel activity in CFS/ME patients. Conclusions: Impaired TRPM3 activity was validated in NK cells isolated from CFS/ME patients using different pharmacological tools and whole-cell patch-clamp technique as the gold standard for ion channel research. This investigation further helps to establish TRPM3 channels as a prognostic marker and/ or a potential therapeutic target for CFS/ME. [ABSTRACT FROM AUTHOR]

By using a back-gate operation, a high-quality two-dimensional electron gas (2DEG) is formed in an undoped GaAs/AlGaAs inverted heterostructure. A high mobility of around 3×10[sup 6] cm[sup 2]/V s at 1.6 K is obtained for the structure without any compensating surface doping. The electron density is controllable down to 7×10[sup 9] cm[sup -2]. The relation between electron density and mobility is studied for samples both with and without a surface gate. The obtained results indicate that background impurities and an inhomogeneity of the electric field coming from the surface govern the mobility in a low-electron-density region and that the interface inhomogeneity becomes important at a high electron density. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We experimentally investigate the width of extended states in disorder-broadened Landau levels (LLs) in top-gated epitaxial graphene on silicon carbide using two different methods: gated transport spectroscopy and activation gap measurements on integer quantum Hall states. The transport spectroscopy reveals that the widths of the extended states in the zero-energy (N = 0) and first excited (TV = 1) LLs are of similar magnitude over the ranges of magnetic field (4-16 T) and temperature studied (1.6-150 K). Under certain assumptions we find that the extended-state width follows a power-law temperature dependence with the exponent η ~ 0.3 in the N = 0 (N = 1) LL, with almost no (very weak) magnetic-field dependence. Activation gap measurements at the filling factors of v = 2 and 6 give results consistent with transport spectroscopy for the N = 1 LL, but indicate a larger broadening for the N = 0 LL than deduced from the spectroscopy. [ABSTRACT FROM AUTHOR]

We report a frequency-conversion technique for edge magnetoplasmons in a quantum Hall device. The nonlinear conductance of a quantum point contact (QPC) results in the generation of high harmonics of an input microwave and the mixing of two input frequencies. We controlled the conversion efficiency by tuning the nonlinear conductance via a gate voltage. The amplitudes of the frequency-converted waves agree well with those expected from the measured dc nonlinear conductance. We demonstrate the technique up to our instrumental limit of 12 GHz and show that formation of charge-density waves does not change the nonlinear characteristics of the QPC. [ABSTRACT FROM AUTHOR]

We investigate integer filling factor phases of many-N-electron vertically coupled semiconductor quantum dot artificial molecules when the inter-dot coupling is strong and weak. The experimental results are analyzed within local-spin density- functional theory. Maximum density droplets composed of electrons in both bonding and anti-bonding, or just bonding states are revealed. Interesting isospin physics (i.e., isospin transitions) can occur particularly when the inter-dot coupling is reduced. [Copyright &y& Elsevier]

Local spin density functional theory calculations for double quantum dots are compared with experimental data to explain the evolution of addition energy spectra with the interdot distance. Realistic features such as finite thickness and nonidentical constituent dots are included in the calculation. We can thus evaluate the heteronuclear character of the diatomic artificial quantum molecules due to a small unavoidable mismatch introduced in their fabrication. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 [ABSTRACT FROM AUTHOR]

We investigate the dissociation of few-electron circular vertical semiconductor double quantum dot artificial molecules at 0 T as a function of interdot distance. Slight mismatch introduced in the fabrication of the artificial molecules from materials with nominally identical constituent quantum wells induces localization. This offsets the energy levels in the quantum dots by up to 2 meV, and can play a crucial role in the appearance of the addition energy spectra as a function of coupling strength particularly in the weak coupling limit. [Copyright &y& Elsevier]

We demonstrate a method for fabricating induced two-dimensional hole devices in (311)A GaAs. The method uses a metallic p+-GaAs capping layer as an in situ top gate that pins the Fermi energy close to the valence band, thereby allowing very small gate biases to be used to induce a two-dimensional hole system at a AlGaAs/GaAs interface. We present transport data from devices with different levels of background impurities. Modeling the mobility as a function of hole density gives a quantitative measure of the level of disorder and indicates that these systems can be used for a systematic study of the effects of disorder in strongly interacting low-dimensional systems. [ABSTRACT FROM AUTHOR]

Quantum spin Hall insulators (QSHIs), also known as two-dimensional topological insulators, have emerged as an unconventional class of quantum states with insulating bulk and conducting edges originating from nontrivial inverted band structures and have been proposed as a platform for exploring spintronics applications and exotic quasiparticles related to the spin-helical edge modes. Despite theoretical proposals for various materials, however, experimental demonstrations of QSHIs have so far been limited to two systems--HgTe/CdTe and InAs/GaSb--both of which are lattice-matched semiconductor heterostructures. Here, we report transport measurements in yet another realization of a band-inverted heterostructure as a QSHI candidate--InAs/InxGa1-xSb with lattice mismatch. We show that the compressive strain in the InxGa1-xSb layer enhances the band overlap and energy gap. Consequently, high bulk resistivity, two orders of magnitude higher than for InAs/GaSb, is obtained deep in the band-inverted regime. The strain also enhances bulk Rashba spin-orbit splitting, leading to an unusual situation where the Fermi level crosses only one spin branch for electronlike and holelike bands over a wide density range. These properties make this system a promising platform for robust QSHIs with unique spin properties and demonstrate the strain to be an important ingredient for tuning spin-orbit interaction. [ABSTRACT FROM AUTHOR]

We have experimentally identified the exchange-induced spin blockade in a GaAs double quantum dot. The transport is suppressed only when the eigenstates are well-defined singlet and triplet states, and thus sensitive to dynamic nuclear-spin polarization that causes singlet-triplet mixing. This gives rise to unusual current spectra, such as a sharp current dip and an asymmetric current profile near the triplet resonance of a double quantum dot. Numerical simulations suggest that the current dip is a signature of identical nuclear-spin polarization in the two dots, which is attractive for coherent spin manipulations in a material with nuclear spins. [ABSTRACT FROM AUTHOR]

Studies of spin degrees of freedom near odd-integer filling ?=3 in the second Landau level have engendered conflicting accounts of the spin properties in this regime. Using resistively detected NMR as a probe of local spin density, we explore the nature of the ground state in the quantum Hall regime near ?=3. Our Knight shift measurements reveal anomalies in NMR spectral line shapes near ?=3, which demonstrate the presence of solid phases formed from charged quasiparticles, with maximal spin polarization (i.e., no additional spin flips) at each ?. The long nuclear spin relaxation times demonstrate the absence of Skyrmions, or spin textures, in this phase. On the basis of these observations, we attempt to reconcile conflicting reports on the quasiparticle properties and spin wave excitations at ?~3, which may engender new paradigms for the understanding of spin excitations in a collinear ferromagnet with broken translational symmetry. [ABSTRACT FROM AUTHOR]

When the motion of electrons is restricted to a plane under a perpendicular magnetic field, a variety of quantum phases emerge at low temperatures, the properties of which are dictated by the Coulomb interaction and its interplay with disorder. At very strong magnetic field, the sequence of fractional quantum Hall liquid phases terminates in an insulating phase, which is widely believed to be due to the solidification of electrons into domains possessing Wigner crystal order. The existence of such Wigner crystal domains is signalled by the emergence of microwave pinning-mode resonances, which reflect the mechanical properties characteristic of a solid. However, the most direct manifestation of the broken translational symmetry accompanying the solidification-the spatial modulation of particles' probability amplitudes-has not been observed yet. Here, we demonstrate that nuclear magnetic resonance provides a direct probe of the density topography of electron solids in the integer and fractional quantum Hall regimes. The data uncover quantum and thermal fluctuations of lattice electrons resolved on the nanometre scale. Our results pave the way to studies of other exotic phases with non-trivial spatial spin/charge order. [ABSTRACT FROM AUTHOR]

The tunneling rates for spin-up and -down electrons are investigated for a GaAs quantum dot in an in-plane magnetic field by using a real-time single-electron counting scheme with a nearby charge detector. An extremely small spin-polarized current on the order of attoamperes is analyzed with the spin and energy dependences of the tunneling rates. Fully spin-polarized current is obtained when only a spin-up Zeeman sublevel is located in the transport window. When both Zeeman sublevels are allowed to contribute to the transport, we find that the tunneling rate for spin-up electrons is considerably higher than that for spin-down electrons. This partially spin-polarized current can be explained by the exchange-enhanced spin splitting in low-density regions near the tunneling barriers. [ABSTRACT FROM AUTHOR]

The model of interacting fermion systems in one dimension known as a Tomonaga-Luttinger liquid (TLL) provides a simple and exactly solvable theoretical framework that predicts various intriguing physical properties. Evidence of a TLL has been observed as power-law behaviour in electronic transport on various types of one-dimensional conductor. However, these measurements, which rely on d.c. transport involving electron tunneling processes, cannot identify the long-awaited hallmark of charge fractionalization, in which an injection of elementary charge e from a non-interacting lead is divided into the non-trivial effective charge e* and the remainder, e−e* (refs 6, 7, 8). Here, we report time-resolved transport measurements on an artificial TLL composed of coupled integer quantum Hall edge channels, in which we successfully identify single charge fractionalization processes. A wave packet of charge q incident from a non-interacting region breaks up into several fractionalized charge wave packets at the edges of the artificial TLL, from which transport eigenmodes can be evaluated directly. These results are informative for elucidating the nature of TLLs and low-energy excitations in the edge channels. [ABSTRACT FROM AUTHOR]

We demonstrate experimentally that graphene quantum capacitance Cq can have a strong impact on transport spectroscopy through the interplay with nearby charge reservoirs. The effect is elucidated in a field-effect-gated epitaxial graphene device, in which interface states serve as charge reservoirs. The Fermi-level dependence of Cq is manifested as an unusual parabolic gate voltage (Vg) dependence of the carrier density, centered on the Dirac point. Consequently, in high magnetic fields B, the spectroscopy of longitudinal resistance (Rxx ) vs Vg represents the structure of the unequally spaced relativistic graphene Landau levels (LLs). Rxx mapping vs Vg and B thus reveals the vital role of the zero-energy LL on the development of the anomalously wide v = 2 quantum Hall state. [ABSTRACT FROM AUTHOR]

By means of sequential and cotunneling spectroscopy, we study the tunnel couplings between metallic leads and individual levels in a carbon nanotube quantum dot. The levels are ordered in shells consisting of two doublets with strong- and weak-tunnel couplings, leading to gate-dependent level renormalization. By comparison to a one- and two-shell model, this is shown to be a consequence of disorder-induced valley mixing in the nanotube. Moreover, a parallel magnetic field is shown to reduce this mixing and thus suppress the effects of tunnel renormalization. [ABSTRACT FROM AUTHOR]

The fractional quantum Hall (FQH) effect at filling factor v = 5/2 has recently come under close scrutiny, as its ground state may possess quasi-particle excitations obeying nonabelian statistics, a property sought for topologically protected quantum operations. However, its microscopic origin remains unknown, and candidate model wave functions include those with undesirable abelian statistics. We report direct measurements of the electron spin polarization of the v = 5/2 FQH state using resistively detected nuclear magnetic resonance. We find the system to be fully polarized, which unambiguously rules out the most likely abelian contender and lends strong support for the v = 5/2 state being nonabelian. Our measurements reveal an intrinsically different nature of interaction in the first excited Landau level underlying the physics at v = 5/2. [ABSTRACT FROM AUTHOR]

We investigate how the orbital magnetic moments of electron and hole states in a carbon nanotube quantum dot depend on the number of carriers on the dot. Low temperature transport measurements are carried out in a setup where the device can be rotated in an applied magnetic field, thus enabling accurate alignment with the nanotube axis. The field dependence of the level structure is measured by excited state spectroscopy and excellent correspondence with a single-particle calculation is found. In agreement with band structure calculations we find a decrease of the orbital magnetic moment with increasing electron or hole occupation of the dot, with a scale given by the band gap of the nanotube. [ABSTRACT FROM AUTHOR]

Background and Purpose: Transient receptor potential canonical 5 (TRPC5) channels are widely expressed, including in the CNS, where they potentiate fear responses. They also contribute to other non-selective cation channels that are stimulated by G-protein-coupled receptor agonists and lipid and redox factors. Steroids are known to modulate fear and anxiety states, and we therefore investigated whether TRPC5 exhibited sensitivity to steroids.Experimental Approach: Human TRPC5 channels were conditionally expressed in HEK293 cells and studied using intracellular Ca2+ measurement, whole-cell voltage-clamp and excised patch techniques. For comparison, control experiments were performed with cells lacking TRPC5 channels or expressing another TRP channel, TRPM2. Native TRPC channel activity was recorded from vascular smooth muscle cells.Key Results: Extracellular application of pregnenolone sulphate, pregnanolone sulphate, pregnanolone, progesterone or dihydrotestosterone inhibited TRPC5 activity within 1-2min. Dehydroepiandrosterone sulphate or 17β-oestradiol had weak inhibitory effects. Pregnenolone, and allopregnanolone, a progesterone metabolite and stereo-isomer of pregnanolone, all had no effects. Progesterone was the most potent of the steroids, especially against TRPC5 channel activity evoked by sphingosine-1-phosphate. In outside-out patch recordings, bath-applied progesterone and dihydrotestosterone had strong and reversible effects, suggesting relatively direct mechanisms of action. Progesterone inhibited native TRPC5-containing channel activity, evoked by oxidized phospholipid.Conclusions and Implications: Our data suggest that TRPC5 channels are susceptible to relatively direct and rapid stereo-selective steroid modulation, leading to channel inhibition. The study adds to growing appreciation of TRP channels as non-genomic steroid sensors. [ABSTRACT FROM AUTHOR]

Understanding how the orbital motion of electrons is coupled to the spin degree of freedom in nanoscale systems is central for applications in spin-based electronics and quantum computation. Here we demonstrate such spin-orbit coupling in a carbon-nanotube quantum dot in the general multielectron regime and in the presence of finite disorder. Also, we find a systematic dependence of the spin-orbit coupling on the electron occupation of the quantum dot. Such a dependence has not been seen in any other system and follows from the curvature-induced spin-orbit-split Dirac spectrum of the underlying graphene lattice. Our findings suggest that the spin-orbit coupling is a general property of carbon-nanotube quantum dots, which should provide a unique platform for the study of spin-orbit effects and their applications. [ABSTRACT FROM AUTHOR]

Background and Purpose: The transient receptor potential melastatin-3 (TRPM3) channel forms calcium-permeable, non-selective, cationic channels that are stimulated by pregnenolone sulphate (PregS). Here, we aimed to define chemical requirements of this acute steroid action and potentially reveal novel stimulators with physiological relevance.Experimental Approach: We used TRPM3 channels over-expressed in HEK 293 cells, with intracellular calcium measurement and whole-cell patch-clamp recording techniques.Key Results: The stimulation of TRPM3 channels was confined to PregS and closely related steroids and not mimicked by other major classes of steroids, including progesterone. Relatively potent stimulation of TRPM3-dependent calcium entry was observed. A sulphate group positioned at ring A was important for strong stimulation but more striking was the requirement for a cis (beta) configuration of the side group, revealing previously unrecognized stereo-selectivity and supporting existence of a specific binding site. A cis-oriented side group on ring A was not the only feature necessary for high activity because loss of the double bond in ring B reduced potency and loss of the acetyl group at ring D reduced efficacy and potency. Weak steroid stimulators of TRPM3 channels inhibited effects of PregS, suggesting partial agonism. In silico screening of chemical libraries for non-steroid modulators of TRPM3 channels revealed the importance of the steroid backbone for stimulatory effects.Conclusions and Implications: Our data defined some of the chemical requirements for acute stimulation of TRPM3 channels by steroids, supporting the existence of a specific and unique steroid binding site. Epipregnanolone sulphate was identified as a novel TRPM3 channel stimulator. [ABSTRACT FROM AUTHOR]

Abstract: In this work we study the Zeeman splitting in induced ballistic 1D wires fabricated along two orthogonal crystallographic directions and . Our data shows that the g-factor anisotropy for the high symmetry direction can be explained by the 1D confinement only, whereas in the case of direction, the interaction between the 1D confinement and crystal anisotropy effects is evident. [Copyright &y& Elsevier]

Abstract: We investigate two closely spaced 2D electron systems in a quasi-Corbino geometry with independent contacts to both layers. Magneto-transport and drag experiments show that at the systems total filling factor 1 the drive current diminishes with increasing interlayer interaction (parameterized by the ratio of layer separation and magnetic length) while voltages of equal magnitude build up over both the drive and the drag layer. The identity of both voltages is resilient to thermal perturbations which contrasts markedly to the behavior observed in Hall bars. [Copyright &y& Elsevier]

Two-dimensional (2D) electronic systems can exhibit dramatic drops in resistivity, ρxx, as the temperature T→0, which has renewed debate as to whether 2D systems may have a metallic ground state. The metallic behaviour is only observed in low-disorder systems, where interactions between the carriers are strong. However, the strength of the metallic behaviour is not universal, with decreases in resistivity ranging from a few per cent to an order of magnitude as T→0. Here, we compare the metallic behaviour in 2D systems dominated by long- and short-range disorder. We thereby highlight the pivotal role played by the type of disorder in determining the strength of metallic behaviour in these systems. In doing so, we resolve recent confusion in the literature that has arisen from the application of interaction-based theories of metallic behaviour to 2D systems whose disorder environments are inconsistent with the assumptions made by these theories. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate a novel heterostructure for inducing 2D hole systems in (311)A GaAs–AlGaAs heterostructures that offers advantages over previous methods including low turn on voltages, easier fabrication and good interface roughness. The heterostructure incorporates a metallic p+-GaAs cap layer as an in situ top gate that pins the Fermi energy close to the valence band and can then be used to induce the 2D hole system at the GaAs/AlGaAs interface. [Copyright &y& Elsevier]

We measured an anisotropic magnetotransport that depends on directions of an in-plane field in a bilayer quantum Hall system. We found that the longitudinal resistance near the bilayer v = 1 quantum Hall state strongly varies when we changed an relative angle between the current and the in-plane field. It is a phenomenon peculiar to the bilayer v = 1 quantum Hail state, because this phenomenon does not appear in a monolayer system. [ABSTRACT FROM AUTHOR]

The tilting angular dependence of the energy gap was measured in the bilayer quantum Hall state at the Landau level filling ν=1 by changing the density imbalance between the two layers. The observed gap behavior shows a continuous transformation from the bilayer balanced density state to the monolayer state. Even a sample with 33 K tunneling gap shows the same activation energy anomaly reported by Murphy et al. (Phys. Rev. Lett. 72 (1994) 728). We discuss a possible relation between our experimental results and the quantum Hall ferromagnet of spins and pseudospins. [Copyright &y& Elsevier]

In a bilayer system, various phase transitions occur due to the competition among the cyclotron, Zeeman and tunneling energies. We investigate effects of an in-plane magnetic field B||, which couples subband and Landau levels with the same spin and modulate wave functions extended to both layers, on transitions of quantum Hall states in such a system. As B|| is applied, we observe that crossings between opposite spin levels as well as those between the same spin levels disappear in characteristic sequences. While anticrossings of single-particle levels are sufficient to explain the observed behavior for crossings at ν=4, the data at ν=6 are not understood in a single-particle picture, and suggest Coulomb-induced mixing of different spin levels. [Copyright &y& Elsevier]

We find spin-dependent enhancement/suppression of scattering between fractional quantum Hall (FQH) edge channels (ECs), which originates from the hyperfine interaction between electron spins and nuclear spins. Nuclear magnetic resonance is detected via the FQH-EC transport, indicating the relevance of dynamic nuclear polarization (DNP). Spin polarizations of FQH ECs are inferred from the DNP. [Copyright &y& Elsevier]

We measured the magnetoresistance in bilayer quantum Hall (QH) state at fractional filling factor ν=2/3. Surprisingly, for different QH areas and two types of hysteresis were observed by controlling the total electron density and the density difference in two layers. Two QH areas and one type of hysteresis are novel characteristic of bilayer systems. [Copyright &y& Elsevier]

We have fabricated and characterized a single hole transistor in an undoped AlGaAs-GaAs heterostructure. Our device consists of a p-type quantum dot, populated using an electric field rather than modulation doping. Low temperature transport measurements reveal periodic conductance oscillations due to Coulomb blockade. We find that the low frequency charge noise is comparable to that in modulation-doped GaAs single electron transistors (SETs), and an order of magnitude better than in silicon SETs. [ABSTRACT FROM AUTHOR]

We demonstrate low temperature operation of an electron-hole bilayer device based on a 40 nm thick layer of silicon in which electrons and holes can be simultaneously induced and contacted independently. The device allows the application of bias between the electrons and holes enhancing controllability over density and confining potential. We confirm that drag measurements are possible with the structure. [ABSTRACT FROM AUTHOR]

We present a method to make Pt nanometer-spaced electrodes that are free of metallic particles and stable at ambient conditions. The nanogaps are fabricated using feedback-controlled electromigration to form few-atom contacts. When performing this procedure at elevated temperatures (>420 K), the Pt contacts undergo self-breaking so that nanometer separated electrode pairs are formed. Once cooled down to lower temperatures, the nanogaps stabilize and can be characterized in detail. We find that current-voltage characteristics can be well fitted to a Simmons model for tunneling and gap-size fluctuations at room temperature determined from these fits stay within 0.6 Å for at least 50 h. [ABSTRACT FROM AUTHOR]

Abstract: We compare directly the metallic behavior of high-quality, two-dimensional hole systems (2DHSs) in two GaAs device structures—one dominated by short-range disorder and the other by long-range disorder. We find that the type of disorder strongly affects the metallic behavior of the 2DHSs. In particular, we find that metallic behavior is enhanced in 2D systems with a high proportion of large-angle scattering events. [Copyright &y& Elsevier]

The authors have fabricated and studied a ballistic one-dimensional p-type quantum wire using an undoped AlGaAs/GaAs heterostructure. The absence of modulation doping eliminates remote ionized impurity scattering and allows high mobilities to be achieved over a wide range of hole densities and, in particular, at very low densities where carrier-carrier interactions are strongest. The device exhibits clear quantized conductance plateaus with highly stable gate characteristics. These devices provide opportunities for studying spin-orbit coupling and interaction effects in mesoscopic hole systems in the strong interaction regime where rs>10. [ABSTRACT FROM AUTHOR]

We investigate the relationship between the Zeeman interaction and the inversion-asymmetry-induced spin-orbit interactions (Rashba and Dresselhaus SOIs) in GaAs hole quantum point contacts. The presence of a strong SOI results in the crossing and anticrossing of adjacent spin-split hole subbands in a magnetic field. We demonstrate theoretically and experimentally that the anticrossing energy gap depends on the interplay between the SOI terms and the highly anisotropic hole g tensor and that this interplay can be tuned by selecting the crystal axis along which the current and magnetic field are aligned. Our results constitute the independent detection and control of the Dresselhaus and Rashba SOIs in hole systems, which could be of importance for spintronics and quantum information applications. [ABSTRACT FROM AUTHOR]