R. Giraud

CEA Grenoble

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Joseph Dufouleur

Leibniz Institute for Solid State and Materials Research

B. Büchner

Leibniz Institute for Solid State and Materials Research

Louis Veyrat

Leibniz Institute for Solid State and Materials Research

B. Barbara

Centre National de la Recherche Scientifique

Saicharan Aswartham

Leibniz Institute for Solid State and Materials Research

Silke Hampel

Leibniz Institute for Solid State and Materials Research

Grigory Shipunov

Leibniz Institute for Solid State and Materials Research

Arthur Veyrat

Laboratoire de physique des Solides

Federico Caglieris

Superconducting and other Innovative Materials and Devices Institute

D. Mailly

Centre National de la Recherche Scientifique

Cooperative Institutions

Centre National de la Recherche Scientifique

Leibniz Institute for Solid State and Materials Research

TU Dresden

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Université Grenoble Alpes

CEA Grenoble

Institut polytechnique de Grenoble

Université Joseph Fourier

Complexity and Topology in Quantum Matter

Université Paris-Saclay

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Direct Deposition of (Bi_xSb_1–x)₂Te₃ Nanosheets on Si/SiO₂ Substrates by Chemical Vapor Transport

Crystal Growth & Design (2022)

Felix Hansen Rico Fucke Titouan Charvin Samuel Froeschke Daniel Wolf

The tellurides of bismuth and antimony (Bi2Te3 and Sb2Te3) are prominent members of the V2VI3 material family that exhibit promising topological properties. We provide a method for the rational synthesis of mixed crystals of these materials ((BixSb1–x)2Te3 with x = 0.1, ..., 0.9) by means of a bottom-up chemical vapor transport (CVT) approach. Thermodynamic calculations showed the synthesis to be possible in the temperature range of 390–560 °C without significant enrichment of either component and without adding a transport agent. The starting materials were synthesized and verified by X-ray diffraction (XRD). Optimization experiments showed the ideal conditions for nanosheet synthesis to be T2 = 560 °C, T1 = 390 °C with a reaction time of t = 36 h. Crystals with heights of down to 12 nm (12 quintuple layers) were synthesized and analyzed by means of scanning electron microscopy, energy-dispersive X-ray spectrometry, and atomic force microscopy. High-resolution transmission electron microscopy confirmed the R3̅m crystal structure, high crystallinity, and overall quality of the synthesized (BixSb1–x)2Te3 nanosheets. Magnetotransport measurements revealed that such ternary compounds can have a significantly reduced carrier density compared to the binary parent compounds.

Bismuth

Ternary compound

Nanosheet

10.1021/acs.cgd.1c01446

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Citations (1)

Non-Hermitian topology in a multi-terminal quantum Hall device

Nature Physics (2024)

Kyrylo Ochkan Raghav Chaturvedi Viktor Könye Louis Veyrat R. Giraud

Reciprocity

10.1038/s41567-023-02337-4

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Citations (16)

Universal Conductance Fluctuations in Epitaxial GaMnAs Ferromagnets: Dephasing by Structural and Spin Disorder

Physical Review Letters (2007)

L. Vila R. Giraud L. Thevenard A. Lemaı̂tre F. Pierre

Mesoscopic transport measurements reveal a large effective phase coherence length in epitaxial GaMnAs ferromagnets, contrary to usual 3d-metal ferromagnets. Universal conductance fluctuations of single nanowires are compared for epilayers with a tailored anisotropy. At large magnetic fields, quantum interferences are due to structural disorder only, and an unusual behavior related to hole-induced ferromagnetism is evidenced, for both quantum interferences and decoherence. At small magnetic fields, phase coherence is shown to persist down to zero field, even in presence of magnons, and an additional spin disorder contribution to quantum interferences is observed under domain walls nucleation.

Mesoscopic physics

Dephasing

Magnon

10.1103/physrevlett.98.027204

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Citations (41)

Large phase coherence effects in GaMnAs-based nanostructures: Towards a quantum spintronics

Applied Surface Science (2007)

R. Giraud L. Vila A. Lemaı̂tre G. Faini

Biasing

Realization (probability)

10.1016/j.apsusc.2007.07.088

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Citations (4)

A Two-Dimensional Electron Gas at the Spinel/Perovskite Interface of γ-Al2O3/SrTiO3 with Carrier Mobility Exceeding 100,000 cm2V-1s-1

Yunzhong Chen N. Bovet Felix Trier Dennis Valbjørn Christensen Fanming Qu

Electron Mobility

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Ferromagnetic Ga _{1 − x} Mn _x N epilayers vs. antiferromagnetic GaMn ₃ N clusters

EPL (Europhysics Letters) (2004)

R. Giraud Shinji Kuroda S. Marcet E. Bellet‐Amalric X. Biquard

Mn-doped wurtzite GaN epilayers have been grown by nitrogen plasma-assisted molecular beam epitaxy. Correlated SIMS, structural and magnetic measurements show that the incorporation of Mn strongly depends on the conditions of the growth. Hysteresis loops which persist at high temperature do not appear to be correlated to the presence of Mn. Samples with up to 2% Mn are purely substitutional Ga$_{1-x}$Mn$_x$N epilayers, and exhibit paramagnetic properties. At higher Mn contents, precipitates are formed which are identified as GaMn$_3$N clusters by x-ray diffraction and absorption: this induces a decrease of the paramagnetic magnetisation. Samples co-doped with enough Mg exhibit a new feature: a ferromagnetic component is observed up to $T_c\sim175$ K, which cannot be related to superparamagnetism of unresolved magnetic precipitates.

Superparamagnetism

Wurtzite crystal structure

Magnetic semiconductor

10.1209/epl/i2003-10120-5

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Citations (47)

Flight hardware and software operations performance review for BAMMsat-on-BEXUS – a BioCubeSat prototype flown on BEXUS30

4th Symposium on Space Educational Activities (2022)

Mateusz Zalasiewicz Aqeel Shamsul Giovanni Sinclair Adrien Bolliand R. Giraud

BAMMsat-on-BEXUS is a student-led project in which a CubeSat-compatible payload was designed, manufactured, and flown on the BEXUS30 stratospheric balloon. The prototype payload – BAMMsat (Biology, Astrobiology, Medicine, and Materials Science on satellite) – is a modular CubeSat-compatible miniaturised laboratory termed a bioCubeSat. The core flight objective was to perform technology demonstration of the bioCubeSat technology, demonstrating capability to perform experiments in space, and to understand system performance and identify future requirements. The mission aimed to validate pre-flight, flight, and post-flight operations, with a focus on biological and autonomous operations and the novel payload hardware. C. elegans samples were flown in the payload. The mission was partially successful, as the BAMMsat systems and autonomous software operated successfully despite challenging conditions and a large volume of payload performance data was collected; however there were issues maintaining the viability of the samples during flight and microfluidic system issues that impeded sample containment and imaging operations. Post-flight analysis has been performed, the root causes of the issues identified, and upgraded novel payload hardware is currently being developed and tested.

Payload (computing)

CubeSat

Space research

International Space Station

10.5821/conference-9788419184405.116

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Very Large Tunneling Anisotropic Magnetoresistance of a(Ga,Mn)As/G…

Physical Review Letters (2005)

C. Rüster C. Gould T. Jungwirth Jairo Sinova G. M. Schott

We report the discovery of a very large tunneling anisotropic magnetoresistance in an epitaxially grown $(\mathrm{G}\mathrm{a},\mathrm{M}\mathrm{n})\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/(\mathrm{G}\mathrm{a},\mathrm{M}\mathrm{n})\mathrm{A}\mathrm{s}$ structure. The key novel spintronics features of this effect are as follows: (i) both normal and inverted spin-valve-like signals; (ii) a large nonhysteretic magnetoresistance for magnetic fields perpendicular to the interfaces; (iii) magnetization orientations for extremal resistance are, in general, not aligned with the magnetic easy and hard axis; (iv) enormous amplification of the effect at low bias and temperatures.

10.1103/physrevlett.94.027203

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Citations (149)

Ultraviolet photodissociation and collision-induced dissociation for qualitative/quantitative analysis of low molecular weight compounds by liquid chromatography-mass spectrometry

Analytical and Bioanalytical Chemistry (2023)

R. Giraud Yves J. C. Le Blanc Mircea Guna Gérard Hopfgartner

Collision-induced dissociation (CID) is the most wildly used fragmentation technique for qualitative and quantitative determination of low molecular weight compounds (LMWC). Ultraviolet photodissociation (UVPD) has been mainly investigated for the analysis of peptides and lipids while only in a limited way for LMWC. A triple quadrupole linear ion trap instrument has been modified to allow ultraviolet photodissociation (UVPD) in the end of the q2 region enabling various workflows with and without data-dependent acquisition (DDA) combining CID and UVPD in the same LC-MS analysis. The performance of UVPD, with a 266-nm laser, is compared to CID for a mix of 90 molecules from different classes of LMWC including peptides, pesticides, pharmaceuticals, metabolites, and drugs of abuse. These two activation methods offer complementary fragments as well as common fragments with similar sensitivities for most analytes investigated. The versatility of UVPD and CID is also demonstrated for quantitative analysis in human plasma of bosentan and its desmethyl metabolite, used as model analytes. Different background signals are observed for both fragmentation methods as well as unique fragments which opens the possibility of developing a selective quantitative assay with improved sample throughput, in particular for analytes present in different matrices.

Quadrupole ion trap

Fragmentation

Ultraviolet

Collision-induced dissociation

10.1007/s00216-023-04977-0

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Citations (1)

Structural and magnetic properties of a Ga0.985Mn0.015N epilayer

Journal of Magnetism and Magnetic Materials (2004)

R. Giraud Shinji Kuroda S. Marcet E. Bellet‐Amalric X. Biquard

Magnetic semiconductor

Hysteresis

10.1016/j.jmmm.2003.12.804

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Citations (5)