31 results on '"G. Gervais"'
Search Results
2. Large composite fermion effective mass at filling factor 5/2.
- Author
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Petrescu M, Berkson-Korenberg Z, Vijayakrishnan S, West KW, Pfeiffer LN, and Gervais G
- Abstract
The 5/2 fractional quantum Hall effect in the second Landau level of extremely clean two-dimensional electron gases has attracted much attention due to its topological order predicted to host quasiparticles that obey non-Abelian quantum statistics and could serve as a basis for fault-tolerant quantum computations. While previous works have establish the Fermi liquid (FL) nature of its putative composite fermion (CF) normal phase, little is known regarding its thermodynamics properties and as a result its effective mass is entirely unknown. Here, we report on time-resolved specific heat measurements at filling factor 5/2, and we examine the ratio of specific heat to temperature as a function of temperature. Combining these specific heat data with existing longitudinal thermopower data measuring the entropy in the clean limit we find that, unless a phase transition/crossover gives rise to large specific heat anomaly, both datasets point towards a large effective mass in the FL phase of CFs at 5/2. We estimate the effective-to-bare mass ratio m
* /me to be ranging from ~ 2 to 4, which is two to three times larger than previously measured values in the first Landau level., (© 2023. The Author(s).)- Published
- 2023
- Full Text
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3. Anomalous electronic transport in high-mobility Corbino rings.
- Author
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Vijayakrishnan S, Poitevin F, Yu O, Berkson-Korenberg Z, Petrescu M, Lilly MP, Szkopek T, Agarwal K, West KW, Pfeiffer LN, and Gervais G
- Abstract
We report low-temperature electronic transport measurements performed in two multi-terminal Corbino samples formed in GaAs/Al-GaAs two-dimensional electron gases (2DEG) with both ultra-high electron mobility ( ≳ 20 × 10
6 cm2 / Vs) and with distinct electron density of 1.7 and 3.6 × 1011 cm-2 . In both Corbino samples, a non-monotonic behavior is observed in the temperature dependence of the resistance below 1 K. Surprisingly, a sharp decrease in resistance is observed with increasing temperature in the sample with lower electron density, whereas an opposite behavior is observed in the sample with higher density. To investigate further, transport measurements were performed in large van der Pauw samples having identical heterostructures, and as expected they exhibit resistivity that is monotonic with temperature. Finally, we discuss the results in terms of various lengthscales leading to ballistic and hydrodynamic electronic transport, as well as a possible Gurzhi effect., (© 2023. The Author(s).)- Published
- 2023
- Full Text
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4. Competing Charge Density Waves Probed by Nonlinear Transport and Noise in the Second and Third Landau Levels.
- Author
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Bennaceur K, Lupien C, Reulet B, Gervais G, Pfeiffer LN, and West KW
- Abstract
Charge density waves (CDWs) in the second and third Landau levels (LLs) are investigated by both nonlinear electronic transport and noise. The use of a Corbino geometry ensures that only bulk properties are probed, with no contribution from edge states. Sliding transport of CDWs is revealed by narrow band noise in reentrant quantum Hall states R2a and R2c of the second LL, as well as in pinned CDWs of the third LL. Competition between various phases-stripe, pinned CDW, or fractional quantum Hall liquid-in both LLs are clearly revealed by combining noise data with maps of conductivity versus magnetic field and bias voltage.
- Published
- 2018
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5. Mechanical Flip-Chip for Ultra-High Electron Mobility Devices.
- Author
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Bennaceur K, Schmidt BA, Gaucher S, Laroche D, Lilly MP, Reno JL, West KW, Pfeiffer LN, and Gervais G
- Abstract
Electrostatic gates are of paramount importance for the physics of devices based on high-mobility two-dimensional electron gas (2DEG) since they allow depletion of electrons in selected areas. This field-effect gating enables the fabrication of a wide range of devices such as, for example, quantum point contacts (QPC), electron interferometers and quantum dots. To fabricate these gates, processing is usually performed on the 2DEG material, which is in many cases detrimental to its electron mobility. Here we propose an alternative process which does not require any processing of the 2DEG material other than for the ohmic contacts. This approach relies on processing a separate wafer that is then mechanically mounted on the 2DEG material in a flip-chip fashion. This technique proved successful to fabricate quantum point contacts on both GaAs/AlGaAs materials with both moderate and ultra-high electron mobility.
- Published
- 2015
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6. Two-dimensional magnetotransport in a black phosphorus naked quantum well.
- Author
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Tayari V, Hemsworth N, Fakih I, Favron A, Gaufrès E, Gervais G, Martel R, and Szkopek T
- Abstract
Black phosphorus (bP) is the second known elemental allotrope with a layered crystal structure that can be mechanically exfoliated to atomic layer thickness. Unlike metallic graphite and semi-metallic graphene, bP is a semiconductor in both bulk and few-layer form. Here we fabricate bP-naked quantum wells in a back-gated field effect transistor geometry with bP thicknesses ranging from 6±1 nm to 47±1 nm. Using a polymer encapsulant, we suppress bP oxidation and observe field effect mobilities up to 900 cm(2) V(-1) s(-1) and on/off current ratios exceeding 10(5). Shubnikov-de Haas oscillations observed in magnetic fields up to 35 T reveal a 2D hole gas with Schrödinger fermion character in a surface accumulation layer. Our work demonstrates that 2D electronic structure and 2D atomic structure are independent. 2D carrier confinement can be achieved without approaching atomic layer thickness, advantageous for materials that become increasingly reactive in the few-layer limit such as bP.
- Published
- 2015
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7. Critical flow and dissipation in a quasi-one-dimensional superfluid.
- Author
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Duc PF, Savard M, Petrescu M, Rosenow B, Del Maestro A, and Gervais G
- Abstract
In one of the most celebrated examples of the theory of universal critical phenomena, the phase transition to the superfluid state of (4)He belongs to the same three-dimensional (3D) O(2) universality class as the onset of ferromagnetism in a lattice of classical spins with XY symmetry. Below the transition, the superfluid density ρs and superfluid velocity v s increase as a power law of temperature described by a universal critical exponent that is constrained to be identical by scale invariance. As the dimensionality is reduced toward 1D, it is expected that enhanced thermal and quantum fluctuations preclude long-range order, thereby inhibiting superfluidity. We have measured the flow rate of liquid helium and deduced its superfluid velocity in a capillary flow experiment occurring in single 30-nm-long nanopores with radii ranging down from 20 to 3 nm. As the pore size is reduced toward the 1D limit, we observe the following: (i) a suppression of the pressure dependence of the superfluid velocity; (ii) a temperature dependence of v s that surprisingly can be well-fitted by a power law with a single exponent over a broad range of temperatures; and (iii) decreasing critical velocities as a function of decreasing radius for channel sizes below R ≃ 20 nm, in stark contrast with what is observed in micrometer-sized channels. We interpret these deviations from bulk behavior as signaling the crossover to a quasi-1D state, whereby the size of a critical topological defect is cut off by the channel radius.
- Published
- 2015
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8. 1D-1D Coulomb drag signature of a Luttinger liquid.
- Author
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Laroche D, Gervais G, Lilly MP, and Reno JL
- Abstract
One-dimensional (1D) interacting electronic systems exhibit distinct properties when compared to their counterparts in higher dimensions. We report Coulomb drag measurements between vertically integrated quantum wires separated by a barrier only 15 nanometers wide. The temperature dependence of the drag resistance is measured in the true 1D regime where both wires have less than one 1D subband occupied. As a function of temperature, an upturn in the drag resistance is observed below a temperature T* ~ 1.6 kelvin. This crossover in Coulomb drag behavior is consistent with Tomonaga-Luttinger liquid models for the 1D-1D drag between quantum wires.
- Published
- 2014
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9. Differential chemical profiling to identify ozonation by-products of estrone-sulfate and first characterization of estrogenicity in generated drinking water.
- Author
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Bourgin M, Gervais G, Bichon E, Antignac JP, Monteau F, Leroy G, Barritaud L, Chachignon M, Ingrand V, Roche P, and Le Bizec B
- Subjects
- Chemical Fractionation, Endocrine Disruptors pharmacology, Estrone chemistry, Molecular Structure, Tandem Mass Spectrometry methods, Water Pollutants, Chemical toxicity, Drinking Water chemistry, Endocrine Disruptors chemistry, Estrone analogs & derivatives, Ozone chemistry, Water Pollutants, Chemical chemistry, Water Purification methods
- Abstract
For a few years, the concern of water treatment companies is not only focused on the removal of target micropollutants but has been extended to the investigation of potential biologically active by-products generated during the treatment processes. Therefore, some methods dedicated to the detection and structural characterization of such by-products have emerged. However, most of these studies are usually carried out under simplified conditions (e.g. high concentration levels of micropollutants, drastic treatment conditions, use of deionized or ultrapure water) and somewhat unrealistic conditions compared to that implemented in water treatment plants. In the present study, a real field water sample was fortified at the part-per-billion level (50 μg L(-1)) with estrone-3-sulfate (E1-3S) before being ozonated (at 1 mg L(-1)) for 10 min. In a first step, targeted measurements evidenced a degradation of the parent compound (>80%) in 10 min. Secondly, a non-targeted chemical profiling approach derived from metabolomic profiling studies allowed to reveal 11 ozonation by-products, among which 4 were found predominant. The estrogenic activity of these water samples spiked with E1-3S before and after treatment was assessed by the ER-CALUX assay and was found to decrease significantly after 10 min of ozonation. Therefore, this innovative methodological strategy demonstrated its suitability and relevancy for revealing unknown compounds generated from water treatment, and permitted to generate new results regarding specifically the impact of ozonation on estrone-3-sulfate. These results confirm that ozonation is effective at removing E1-3S in drinking water and indicate that the by-products generated have significantly lower estrogenic activity., (Copyright © 2013 Elsevier Ltd. All rights reserved.)
- Published
- 2013
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10. Quantum Hall effect in hydrogenated graphene.
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Guillemette J, Sabri SS, Wu B, Bennaceur K, Gaskell PE, Savard M, Lévesque PL, Mahvash F, Guermoune A, Siaj M, Martel R, Szkopek T, and Gervais G
- Abstract
The quantum Hall effect is observed in a two-dimensional electron gas formed in millimeter-scale hydrogenated graphene, with a mobility less than 10 cm2/V·s and corresponding Ioffe-Regel disorder parameter (k(F)λ)(-1) ≫ 1. In a zero magnetic field and low temperatures, the hydrogenated graphene is insulating with a two-point resistance of the order of 250h/e2. The application of a strong magnetic field generates a negative colossal magnetoresistance, with the two-point resistance saturating within 0.5% of h/2e2 at 45 T. Our observations are consistent with the opening of an impurity-induced gap in the density of states of graphene. The interplay between electron localization by defect scattering and magnetic confinement in two-dimensional atomic crystals is discussed.
- Published
- 2013
- Full Text
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11. Hydrodynamics of superfluid helium in a single nanohole.
- Author
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Savard M, Dauphinais G, and Gervais G
- Abstract
The flow of liquid helium through a single nanohole with radius smaller than 25 nm was studied. Mass flow was induced by applying a pressure difference of up to 1.4 bar across a 50 nm thick Si(3)N(4) membrane and was measured directly by means of mass spectrometry. In liquid He I, we experimentally show that the fluid is not clamped by the short pipe with diameter-to-length ratio D/L≃1, despite the small diameter of the nanohole. This viscous flow is quantitatively understood by making use of a model of flow in short pipes. In liquid He II, a two-fluid model for mass flow is used to extract the superfluid velocity in the nanohole for different pressure heads at temperatures close to the superfluid transition. These velocities compare well to existing data for the critical superflow of liquid helium in other confined systems., (© 2011 American Physical Society)
- Published
- 2011
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12. Positive and negative Coulomb drag in vertically integrated one-dimensional quantum wires.
- Author
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Laroche D, Gervais G, Lilly MP, and Reno JL
- Abstract
Electron interactions in and between wires become increasingly complex and important as circuits are scaled to nanometre sizes, or use reduced-dimensional conductors such as carbon nanotubes, nanowires and gated high-mobility two-dimensional electron systems. This is because the screening of the long-range Coulomb potential of individual carriers is weakened in these systems, which can lead to phenomena such as Coulomb drag, where a current in one wire induces a voltage in a second wire through Coulomb interactions alone. Previous experiments have demonstrated Coulomb electron drag in wires separated by a soft electrostatic barrier of width ≳80 nm (ref. 12), which was interpreted as resulting entirely from momentum transfer. Here, we measure both positive and negative drag between adjacent vertical quantum wires that are separated by ∼15 nm and have independent contacts, which allows their electron densities to be tuned independently. We map out the drag signal versus the number of electron sub-bands occupied in each wire, and interpret the results both in terms of momentum-transfer and charge-fluctuation induced transport models. For wires of significantly different sub-band occupancies, the positive drag effect can be as large as 25%.
- Published
- 2011
- Full Text
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13. Quantum-classical crossover and apparent metal-insulator transition in a weakly interacting 2D Fermi liquid.
- Author
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Zhou X, Schmidt B, Proust C, Gervais G, Pfeiffer LN, West KW, and Sarma SD
- Abstract
We report the observation of an apparent parallel magnetic-field-induced metal-insulator transition in a high-mobility two-dimensional electron gas for which spin and localization physics most likely play no major role. The high-mobility metallic phase at low field is consistent with the established Fermi liquid transport theory including phonon scattering, whereas the phase at higher field shows a large insulatinglike negative temperature dependence at resistances much smaller than the quantum of resistance h/e(2). We argue that this observation is a direct manifestation of a quantum-classical crossover arising predominantly from the magneto-orbital coupling between the finite width of the two-dimensional electron gas and the in-plane magnetic field., (© 2011 American Physical Society)
- Published
- 2011
- Full Text
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14. Differential global profiling as a new analytical strategy for revealing micropollutant treatment by-products: application to ethinylestradiol and chlorination water treatment.
- Author
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Gervais G, Bichon E, Antignac JP, Monteau F, Leroy G, Barritaud L, Chachignon M, Ingrand V, Roche P, and Le Bizec B
- Subjects
- Fresh Water chemistry, Halogenation, Water Purification, Water Supply analysis, Chlorine Compounds analysis, Disinfectants analysis, Environmental Monitoring methods, Ethinyl Estradiol analysis, Water Pollutants, Chemical analysis
- Abstract
The detection and structural elucidation of micropollutants treatment by-products are major issues to estimate efficiencies of the processes employed for drinking water production versus endocrine disruptive compounds contamination. This issue was mainly investigated at the laboratory scale and in high concentration conditions. However, potential by-products generated after chlorination can be influenced by the dilution factor employed in real conditions. The present study proposes a new methodology borrowed to the metabolomic science, using liquid chromatography coupled to high-resolution mass spectrometry, in order to reveal potential chlorination by-products of ethinylestradiol in spiked real water samples at the part-per-billion level (5 μg L(-1)). Conventional targeted measurements first demonstrated that chlorination with sodium hypochlorite (0.8 mg L(-1)) led to removals of ethinylestradiol over 97%. Then, the developed differential global profiling approach permitted to reveal eight chlorination by-products of EE2, six of them being described for the first time. Among these eight halogenated compounds, five have been structurally identified, demonstrating the potential capabilities of this new methodology applied to environmental samples., (Copyright © 2011 Elsevier Ltd. All rights reserved.)
- Published
- 2011
- Full Text
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15. Adiabatic cooling with non-Abelian anyons.
- Author
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Gervais G and Yang K
- Abstract
We show in this Letter that the ground state degeneracy associated with the presence of non-Abelian anyons can be probed by using an adiabatic cooling process based on the non-Abelian entropy. In particular, we show that when the number of such anyons is increased adiabatically at sufficiently low temperatures, the non-Abelian liquid undergoes cooling, whereas heating occurs in the Abelian case. Estimates are provided for the cooling power produced by the non-Abelian anyon refrigerator, and its implementation in non-Abelian fractional quantum Hall liquids is discussed.
- Published
- 2010
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16. Colossal magnetoresistance in an ultraclean weakly interacting 2D Fermi liquid.
- Author
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Zhou X, Piot BA, Bonin M, Engel LW, Das Sarma S, Gervais G, Pfeiffer LN, and West KW
- Abstract
We report the observation of a new phenomenon of colossal magnetoresistance in a 40 nm wide GaAs quantum well in the presence of an external magnetic field applied parallel to the high-mobility 2D electron layer. In a strong magnetic field, the magnetoresistance is observed to increase by a factor of ∼300 from 0 to 45 T without the system undergoing any metal-insulator transition. We discuss how this colossal magnetoresistance effect cannot be attributed to the spin degree of freedom or localization physics, but most likely emanates from strong magneto-orbital coupling between the two-dimensional electron gas and the magnetic field. Our observation is consistent with a field-induced 2D-to-3D transition in the confined electronic system.
- Published
- 2010
- Full Text
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17. Flow conductance of a single nanohole.
- Author
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Savard M, Tremblay-Darveau C, and Gervais G
- Abstract
The mass flow conductance of single nanoholes with a diameter ranging from 75 to 100 nm was measured using mass spectrometry. For all nanoholes, a smooth crossover is observed between single-particle statistical flow (effusion) and the collective viscous flow emanating from the formation of a continuum. This crossover is shown to occur when the gas mean free path matches the size of the nanohole diameter. As a consequence of the pinhole geometry, the breakdown of the Poiseuille approximation is observed in the power-law temperature exponent of the measured conductance.
- Published
- 2009
- Full Text
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18. Contrasting behavior of the 5/2 and 7/3 fractional quantum Hall effect in a tilted field.
- Author
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Dean CR, Piot BA, Hayden P, Das Sarma S, Gervais G, Pfeiffer LN, and West KW
- Abstract
Using a tilted-field geometry, the effect of an in-plane magnetic field on the even denominator nu=5/2 fractional quantum Hall state is studied. The energy gap of the nu=5/2 state is found to collapse linearly with the in-plane magnetic field above approximately 0.5 T. In contrast, a strong enhancement of the gap is observed for the nu=7/3 state. The radically distinct tilted-field behavior between the two states is discussed in terms of Zeeman and magneto-orbital coupling within the context of the proposed Moore-Read Pfaffian wave function for the 5/2 fractional quantum Hall effect.
- Published
- 2008
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19. Ultra-pressure liquid chromatography-electrospray tandem mass spectrometry for multiresidue determination of pesticides in water.
- Author
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Gervais G, Brosillon S, Laplanche A, and Helen C
- Subjects
- Acetonitriles chemistry, Hydrogen-Ion Concentration, Methylene Chloride chemistry, Pesticide Residues analysis, Pesticide Residues isolation & purification, Pesticides isolation & purification, Reproducibility of Results, Solid Phase Extraction, Water Pollutants, Chemical isolation & purification, Chromatography, High Pressure Liquid methods, Pesticides analysis, Spectrometry, Mass, Electrospray Ionization methods, Tandem Mass Spectrometry methods, Water Pollutants, Chemical analysis
- Abstract
A multiresidue analysis method has been developed for the determination of pesticides in water by ultra-performance liquid chromatography (UPLC) combined with tandem mass spectrometry (MS/MS). The selected pesticides represent a broad range of polarity and volatility [benzoylcyclohexanedione (mesotrione and sulcotrione); chloroacetamide (acetochlor, alachlor, dimethenamide, and metolachlor); phenoxyacetic acid (2,4-D and MCPA); phenoxypropionic (dichloprop and mecoprop); phenylurea (chlortoluron, diuron, isoproturon, linuron, and metoxuron); sulfonylurea (foramsulfuron, iodosulfuron, and nicolsulfuron); triazine (atrazine, cyanazine, desethylatrazine (DEA), desisopropylatrazine (DIA), simazine, and terbutylazine)]. The analytes were extracted using solid-phase extraction (SPE). The separation was carried out on an acquity UPLC BEH C18 column (1.7 microm, 50 mm x 1 mm ID) using a gradient elution profile and mobile phase consisting of 0.1% formic acid in water and acetonitrile. The pesticides were detected with a tandem mass spectrometer after being ionised positively or negatively (depending on the molecule) using an electrospray ionisation (ESI) source. To achieve the suitable extraction conditions for sample preparation, several parameters affecting the efficiency of SPE such as the nature of the sorbent and the eluent, extractant volume and pH were studied. The best recovery was obtained by the extraction with an Oasis HLB cartridge and 3 mL of a solution of acetonitrile/dichloromethane (1:1, v/v) at pH 2. The average recoveries of the pesticides in different samples ranged from 82 to 109%. The weight least squares (WLS) linear regression was used to calculate the limits of detection and quantification (LOD and LOQ) because the dispersion was heteroskedastic. All the pesticides could be correctly quantified at a concentration level of 50 ng L(-1) and most of them could be detected at a concentration inferior or equal to 8 ng L(-1). Efficiency and robustness of this method were evaluated by the analysis of several samples of real natural water.
- Published
- 2008
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20. Intrinsic gap of the nu=5/2 fractional quantum Hall state.
- Author
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Dean CR, Piot BA, Hayden P, Das Sarma S, Gervais G, Pfeiffer LN, and West KW
- Abstract
The fractional quantum Hall effect is observed at low magnetic field where the cyclotron energy is smaller than the Coulomb interaction energy. The nu=5/2 excitation gap at 2.63 T is measured to be 262+/-15 mK, similar to values obtained in samples with twice the electronic density. Examining the role of disorder on the 5/2 state, we find that a large discrepancy remains between theory and experiment for the intrinsic gap extrapolated from the infinite mobility limit. The observation of a 5/2 state in the low-field regime suggests that inclusion of nonperturbative Landau level mixing may be necessary to fully understand the energetics of half-filled fractional quantum Hall liquids.
- Published
- 2008
- Full Text
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21. Local control of light polarization with low-temperature fiber optics.
- Author
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Mack AH, Riordon J, Dean CR, Talbot R, and Gervais G
- Subjects
- Algorithms, Arsenicals chemistry, Fiber Optic Technology, Gallium chemistry, Light, Models, Statistical, Models, Theoretical, Optical Fibers, Physics methods, Quantum Theory, Research Design, Semiconductors, Temperature, Optics and Photonics
- Abstract
A fiber-optic-based polarization control system that uses a backreflection measurement scheme at low temperatures has been developed. This provides a stringent test of the light polarization state at the output of the fiber, allowing for determination and control of the degree of circular polarization; i.e., it can generate linear, right, or left circular polarization with cryogenic fibers. This polarization controller is paving the way toward the control and manipulation of nuclear spins in semiconductors via the optical Overhauser effect and could be used, for example, for the purpose of quantum information processing with the large nuclear spins of GaAs.
- Published
- 2007
- Full Text
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22. Evidence for skyrmion crystallization from NMR relaxation experiments.
- Author
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Gervais G, Stormer HL, Tsui DC, Kuhns PL, Moulton WG, Reyes AP, Pfeiffer LN, Baldwin KW, and West KW
- Abstract
A resistively detected NMR technique was used to probe the two-dimensional electron gas in a GaAs/AlGaAs quantum well. The spin-lattice relaxation rate (1/T(1)) was extracted at near complete filling of the first Landau level by electrons. The nuclear spin of (75)As is found to relax much more efficiently with T --> 0 and when a well developed quantum Hall state with R(xx) approximately 0 occurs. The data show a remarkable correlation between the nuclear spin relaxation and localization. This suggests that the magnetic ground state near complete filling of the first Landau level may contain a lattice of topological spin texture, i.e., a Skyrmion crystal.
- Published
- 2005
- Full Text
- View/download PDF
23. Competition between a fractional quantum hall liquid and bubble and Wigner crystal phases in the third Landau level.
- Author
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Gervais G, Engel LW, Stormer HL, Tsui DC, Baldwin KW, West KW, and Pfeiffer LN
- Abstract
Magnetotransport measurements were performed in an ultrahigh mobility GaAs/AlGaAs quantum well of density approximately 3.0 x 10(11) cm(-2). The temperature dependence of the magnetoresistance Rxx was studied in detail in the vicinity of nu=9/2. In particular, we discovered new minima in Rxx at a filling factor nu approximately 41/5 and 44/5, but only at intermediate temperatures 80 approximately less than T approximately less than 120 mK. We interpret these as evidence for a fractional quantum Hall liquid forming in the N=2 Landau level and competing with bubble and Wigner crystal phases favored at lower temperatures. Our data suggest that a magnetically driven insulator-insulator quantum phase transition occurs between the bubble and Wigner crystal phases at T=0.
- Published
- 2004
- Full Text
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24. A1 and A2 transitions in superfluid 3He in 98% porosity aerogel.
- Author
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Choi HC, Gray AJ, Vicente CL, Xia JS, Gervais G, Halperin WP, Mulders N, and Lee Y
- Abstract
Superfluid 3He in high porosity aerogel is the system in which the effects of static impurities on a p-wave superfluid can be investigated in a systematic manner. We performed shear acoustic impedance measurements on this system (98% porosity aerogel) in the presence of magnetic fields up to 15 T at the sample pressures of 28.4 and 33.5 bars. We observed the splitting of the superfluid transition into two transitions in high fields in both bulk and liquid in aerogel. The field dependence of the splitting in aerogel resembles that of the bulk superfluid 3He caused by the presence and growth of the A1 phase. Our results provide the first evidence of the A1 phase in superfluid (3)He/aerogel.
- Published
- 2004
- Full Text
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25. Specific heat of disordered superfluid 3He.
- Author
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Choi H, Yawata K, Haard TM, Davis JP, Gervais G, Mulders N, Sharma P, Sauls JA, and Halperin WP
- Abstract
The specific heat of superfluid 3He, disordered by a silica aerogel, is found to have a sharp discontinuity marking the thermodynamic transition to superfluidity at a temperature reduced from that of bulk 3He. The magnitude of the discontinuity is also suppressed. This disorder effect can be understood from the Ginzburg-Landau theory which takes into account elastic quasiparticle scattering suppressing both the transition temperature and the amplitude of the order parameter. We infer that the limiting temperature dependence of the specific heat is linear at low temperatures in the disordered superfluid state, consistent with predictions of gapless excitations everywhere on the Fermi surface.
- Published
- 2004
- Full Text
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26. Nucleation and interfacial coupling between pure and dirty superfluid phases of 3He.
- Author
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Gervais G, Yawata K, Mulders N, and Halperin WP
- Abstract
The nucleation of the first-order phase transition of superfluid 3He-B from superfluid 3He-A is quite remarkable since it requires a seed of the order of a micron. We have studied this nucleation for 3He confined to a very dilute silica aerogel. This dirty superfluid behaves in a manner similar to previous reports for the pure superfluid. But we have discovered a novel magnetically driven nucleation switch acting on the pure superfluid- B phase. Last, we find the surprising result that the proximity effect between the pure and dirty superfluids at their interface is insufficient to nucleate the B phase in either superfluid.
- Published
- 2002
- Full Text
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27. Modification of the superfluid 3He phase diagram by impurity scattering.
- Author
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Gervais G, Haard TM, Nomura R, Mulders N, and Halperin WP
- Abstract
The effect of impurity scattering on the phase diagram of pure superfluid 3He has been investigated by acoustic techniques near the bulk polycritical pressure. Impurities were introduced with a 98% porous silica aerogel. In zero applied field, the equilibrium phase is a B phase, consistent with predictions from isotropic scattering. The superfluid transition in a magnetic field at 25 bars is from normal to A phase and is independent of the magnetic field up to 2.9 kG. A first-order phase transition between A and B superfluids is observed with surprisingly strong supercooling in both zero and nonzero applied field.
- Published
- 2001
- Full Text
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28. High-frequency acoustics of 3He in aerogel
- Author
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Nomura R, Gervais G, Haard TM, Lee Y, Mulders N, and Halperin WP
- Abstract
High-frequency ( approximately 15 MHz) acoustics were performed on 3He in 98% porous silica aerogel using an acoustic cavity technique. Measurements of the sound attenuation in the normal Fermi liquid and superfluid display behavior quite different from the bulk owing to strong elastic scattering of quasiparticles. The transition from first-to-zero sound is completely obscured with a quasiparticle mean-free path estimated to be in the range of 200-300 nm. No collective mode attenuation peak was observed at or below the superfluid transition.
- Published
- 2000
- Full Text
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29. An interview with Sr. Generose Gervais, OSF, Chairman, CHA Board of Trustees.
- Author
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Gervais G
- Subjects
- Catholicism, Hospital Bed Capacity, 500 and over, Minnesota, United States, Hospital Administration trends, Societies organization & administration, Societies, Hospital organization & administration
- Published
- 1982
30. [Gonad function of women with homogenous karyotype XO or with mosaic form. Five case histories of fertile women (author's transl)].
- Author
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Mavel A, Turc C, Feldman JP, Michiels Y, Nivelon-Chevallier A, Koslowski JP, and Gervais G
- Subjects
- Abnormalities, Multiple, Abortion, Spontaneous etiology, Female, Fertility, Genitalia, Female pathology, Humans, Infant, Newborn, Karyotyping, Male, Menstruation, Mosaicism, Pregnancy, Sex Chromosomes analysis, Pregnancy Complications, Turner Syndrome genetics
- Abstract
The authors report five cases of fertile women who have Karyotype XO. After a short review of the classification of Turner's syndrome and of the physiopathology of the defective gonads in these patients, 79 cases in the literature and these 5 cases were reviewed and they allow us: a precise description of the morphology of these patients, which is dominated by the high incidence of small growth and the presence of the various degrees of malformations often found in Turner's syndrome; to study the gonad structure and function of these patients who have spontaneous menstruation. And finally to analyse the prognosis of pregnancies that have occurred in 33 women with an XO clone. These women have not only a raised incidence of spontaneous abortions at 32% but also frequent fetal malformations and chromosome abnormalities in the products of conception. It is therefore vital to carry out early amniocentesis in these patients.
- Published
- 1980
31. [Use of a rat control service in industrial establishments; technical and practical notes].
- Author
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GERVAIS G and POULAIN P
- Subjects
- Rats, Industry, Work
- Published
- 1951
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