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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Precision Measurement of 1 MΩ Quantum Hall Resistance Array
摘要： We present preliminary results of precision measurements of 1 M? quantum Hall resistance array made of the GaAs/AlGaAs heterosubstrate. Precision measurements have been performed with a cryogenic current comparator resistance bridge by comparing the array resistance to a 10 k? resistance standard traceable to the quantum Hall effect. Stability of the quantization within the relative standard uncertainty of 18 ×10-9 through repeated thermal cycles reflects the invariant quantum nature of the array resistance in a given condition.
关键词： cryogenic current comparator,Quantum Hall effect,quantum Hall resistance array,resistance metrology
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Development of AC Quantum Hall Measurements at CMI
摘要： This paper describes results and equipment involved in experiments with realization of quantum impedance standard, based on ac quantum Hall resistance standard. CMI developed cryogenic probe with TO-8 holder and coaxial wiring, device holder and digitally assisted (DA) bridge suitable for ac measurements of quantum Hall effect. Experiments were performed at liquid helium temperatures with GaAs devices placed in double shielded holders.
关键词： traceability,quantum Hall effect,standards,electrical impedance
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Epitaxial Graphene p-n Junctions
摘要： We report the fabrication and measurement of top gated epitaxial graphene p-n junctions where exfoliated hexgonal boron nitride (hBN) is used as the gate dielectric. The four terminal longitudinal resistance across a single junction is well quantized at RK?90 (= 25812.807 ?) with a relative uncertainty of 10?7. Our work opens the possibility to realize programmable electrical resistance standards using external gating.
关键词： resistance standard,quantum Hall effect,graphene p-n junction,Epitaxial graphene
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Stable and Tunable Charge Carrier Control of Graphene for Quantum Resistance Metrology
摘要： Here we demonstrate a stable and tunable method to alter the carrier concentration of epitaxial graphene grown on silicon carbide. This technique relies on chemical doping by an acceptor molecule. Through careful tuning one can produce chemically doped graphene quantum resistance devices which show long-term stability in ambient conditions and have performance comparable to that of GaAs quantum resistance standards. This development paves the way for controlled device fabrication of graphene quantum hall resistance standards, which can be reliably tailored to operate below 5 T and above 4 K out-of-the-box, without further adjustments from the end-user.
关键词： quantum hall effect,chemical doping,graphene,measurement standards
更新于2025-09-10 09:29:36
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Enhancement in surface mobility and quantum transport of Bi2?xSbxTe3?ySey topological insulator by controlling the crystal growth conditions
摘要： Despite numerous studies on three-dimensional topological insulators (3D TIs), the controlled growth of high quality (bulk-insulating and high mobility) TIs remains a challenging subject. This study investigates the role of growth methods on the synthesis of single crystal stoichiometric BiSbTeSe2 (BSTS). Three types of BSTS samples are prepared using three different methods, namely melting growth (MG), Bridgman growth (BG) and two-step melting-Bridgman growth (MBG). Our results show that the crystal quality of the BSTS depend strongly on the growth method. Crystal structure and composition analyses suggest a better homogeneity and highly-ordered crystal structure in BSTS grown by MBG method. This correlates well to sample electrical transport properties, where a substantial improvement in surface mobility is observed in MBG BSTS devices. The enhancement in crystal quality and mobility allow the observation of well-developed quantum Hall effect at low magnetic field.
关键词： two-step melting-Bridgman growth,three-dimensional topological insulators,surface mobility,quantum Hall effect,Bridgman growth,melting growth,BiSbTeSe2
更新于2025-09-10 09:29:36
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Photoquantum Hall Effect and Light-Induced Charge Transfer at the Interface of Graphene/InSe Heterostructures
摘要： The transfer of electronic charge across the interface of two van der Waals crystals can underpin the operation of a new class of functional devices. Among van der Waals semiconductors, an exciting and rapidly growing development involves the “post-transition” metal chalcogenide InSe. Here, field effect phototransistors are reported where single layer graphene is capped with n-type InSe. These device structures combine the photosensitivity of InSe with the unique electrical properties of graphene. It is shown that the light-induced transfer of charge between InSe and graphene offers an effective method to increase or decrease the carrier density in graphene, causing a change in its resistance that is gate-controllable and only weakly dependent on temperature. The charge transfer at the InSe/graphene interface is probed by Hall effect and photoconductivity measurmentes and it is demonstrated that light can induce a sign reversal of the quantum Hall voltage and photovoltaic effects in the graphene layer. These findings demonstrate the potential of light-induced charge transfer in gate-tunable InSe/graphene phototransistors for optoelectronics and quantum metrology.
关键词： quantum Hall effect,InSe,graphene
更新于2025-09-09 09:28:46
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Quantum Hall effect based on Weyl orbits in Cd3As2
摘要： Discovered decades ago, the quantum Hall effect remains one of the most studied phenomena in condensed matter physics and is relevant for research areas such as topological phases, strong electron correlations and quantum computing1–5. The quantized electron transport that is characteristic of the quantum Hall effect typically originates from chiral edge states—ballistic conducting channels that emerge when two-dimensional electron systems are subjected to large magnetic fields2. However, whether the quantum Hall effect can be extended to higher dimensions without simply stacking two-dimensional systems is unknown. Here we report evidence of a new type of quantum Hall effect, based on Weyl orbits in nanostructures of the three-dimensional topological semimetal Cd3As2. The Weyl orbits consist of Fermi arcs (open arc-like surface states) on opposite surfaces of the sample connected by one-dimensional chiral Landau levels along the magnetic field through the bulk6,7. This transport through the bulk results in an additional contribution (compared to stacked two-dimensional systems and which depends on the sample thickness) to the quantum phase of the Weyl orbit. Consequently, chiral states can emerge even in the bulk. To measure these quantum phase shifts and search for the associated chiral modes in the bulk, we conduct transport experiments using wedge-shaped Cd3As2 nanostructures with variable thickness. We find that the quantum Hall transport is strongly modulated by the sample thickness. The dependence of the Landau levels on the magnitude and direction of the magnetic field and on the sample thickness agrees with theoretical predictions based on the modified Lifshitz–Onsager relation for the Weyl orbits. Nanostructures of topological semimetals thus provide a way of exploring quantum Hall physics in three-dimensional materials with enhanced tunability.
关键词： quantum Hall effect,Cd3As2,Weyl orbits,topological semimetal,chiral Landau levels
更新于2025-09-09 09:28:46
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Electrical Conductivity of Reduced Graphene Oxide Thin-Film Layers
摘要： This work deals with the research of the electric properties of thin film layer of reduced graphene oxide. A structure of graphene oxide (GO) is represented by randomly distributed on a surface of substrate small islets of graphene with sp2 hybridized bonds surrounded by wide areas with sp3 bonds functionalized by oxygen groups. When electrons are confined in two-dimensional materials, quantum-mechanically enhanced transport phenomena such as the quantum Hall effect can be observed. Reduced graphene oxide, consisting of an isolated single atomic layer of graphite, is an ideal realization of such a two-dimensional system, therefore the partly semiconductive properties could be observed.
关键词： electrical conductivity,quantum Hall effect,reduced graphene oxide,thin-film layers,sp2 hybridized bonds
更新于2025-09-04 15:30:14
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Creating, probing, and manipulating fractionally charged excitations of fractional Chern insulators in optical lattices
摘要： We propose a set of schemes to create and probe fractionally charged excitations of a fractional Chern insulator state in an optical lattice. This includes the creation of localized quasiparticles and quasiholes using both static local defects and the dynamical local insertion of synthetic flux quanta. Simulations of repulsively interacting bosons on a finite square lattice with experimentally relevant open boundary conditions show that already a four-particle system exhibits signatures of charge fractionalization in the quantum-Hall-like state at the filling fraction of 1/2 particle per flux quantum. This result is favorable for the prospects of adiabatic preparation of fractional Chern insulators. Our work is inspired by recent experimental breakthroughs in atomic quantum gases: the realization of strong artificial magnetic fields in optical lattices, the ability of single-site addressing in quantum gas microscopes, and the preparation of low-entropy insulating states by engineering an entropy-absorbing metallic reservoir.
关键词： quasiholes,quantum Hall effect,quasiparticles,optical lattices,fractional Chern insulators
更新于2025-09-04 15:30:14
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Nonuniversal Scaling Behavior of Conductivity Peak Widths in the Quantum Hall Effect in InGaAs/InAlAs Structures
摘要： The longitudinal ρxx and Hall ρxy resistances were measured in the region of the quantum phase transitions for the quantum Hall effect regime with magnetic fields up to 12 T at temperatures of T = 0.4–30 K in two-dimensional electron systems n-In0.9Ga0.1As/In0.81Al0.19As. The nonuniversal scaling behavior of the temperature dependence of the width of the resistance ρxx peaks related to the effect of the large-scale random potential and of Landau-level mixing with opposite spin directions was found.
关键词： quantum Hall effect,random potential,scaling behavior,InGaAs/InAlAs structures,Landau-level mixing
更新于2025-09-04 15:30:14