Magnetotransport properties of graphene layers decorated with colloid quantum dots

The hybrid graphene-quantum dot devices can potentially be used to tailor the electronic, optical, and chemical properties of graphene. Here, the low temperature electronic transport properties of bilayer graphene decorated with PbS colloid quantum dots(CQDs) have been investigated in the weak or strong magnetic fields. The presence of the CQDs introduces additional scattering potentials that alter the magnetotransport properties of the graphene layers, leading to the observation of a new set of magnetoconductance oscillations near zero magnetic field as well as the high-field quantum Hall regime.The results bring about a new strategy for exploring the quantum interference effects in two-dimensional materials which are sensitive to the surrounding electrostatic environment, and open up a new gateway for exploring the graphene sensing with quantum interference effects.

A double quantum dot defined by top gates in a single crystalline InSb nanosheet

We report on the transport study of a double quantum dot(DQD)device made from a freestanding,single crystalline InSb nanosheet.The freestanding nanosheet is grown by molecular beam epitaxy and the DQD is defined by the top gate technique.Through the transport measurements,we demonstrate how a single quantum dot(QD)and a DQD can be defined in an InSb nanosheet by tuning voltages applied to the top gates.We also measure the charge stability diagrams of the DQD and show that the charge states and the inter-dot coupling between the two individual QDs in the DQD can be efficiently regulated by the top gates.Numerical simulations for the potential profile and charge density distribution in the DQD have been performed and the results support the experimental findings and provide a better understanding of fabrication and transport characteristics of the DQD in the InSb nanosheet.The achieved DQD in the two-dimensional InSb nanosheet possesses pronounced benefits in lateral scaling and can thus serve as a new building block for the developments of quantum computation and quantum simulation technologies.

Electrical and thermoelectric study of two-dimensional crystal of NbSe2

We report experimental investigation of the resistivity and Nernst effect in two-dimensional(2D)NbSe2 crystals.A strongly enhanced Nernst effect,100 times larger than that in bulk NbSe2,caused by moving vortices is observed in thin film.It is found that in the low temperature,high magnetic field regime,pinning effects show little dependence on the thickness and resistivity of the superconductor films.Strong Nernst signals persist above the superconducting transition,suggesting that the Nernst effect is a sensitive probe to superconducting fluctuations.A magnetic field induced superconductor-insulator transition(SIT)is evident,which is surprising in that such a SIT usually takes place in disordered dirty superconductors,while our samples are highly crystalline and close to the clean limit.Hence,our results expand the scope of SIT into 2D crystal clean superconductors.

Quantum oscillations in a hexagonal boron nitride-supported single crystalline InSb nanosheet

A gated Hall-bar device is made from an epitaxially grown,free-standing InSb nanosheet on a hexagonal boron nitride(hBN)dielectric/graphite gate structure and the electron transport properties in the InSb nanosheet are studied by gate-transfer characteristic and magnetotransport measurements at low temperatures.The measurements show that the carriers in the InSb nanosheet are of electrons and the carrier density in the nanosheet can be highly efficiently tuned by the graphite gate.The mobility of the electrons in the InSb nanosheet is extracted from low-field magneotransport measurements and a value of the mobility exceeding~1.8×10^(4) cm^(2)·V^(-1)·s^(-1) is found.High-field magentotransport measurements show well-defined Shubnikov-de Haas(SdH)oscillations in the longitudinal resistance of the InSb nanosheet.Temperature-dependent measurements of the SdH oscillations are carried out and key transport parameters,including the electron effective mass m*~0.028m0 and the quantum lifetimeτ~0.046 ps,in the InSb nanosheet are extracted.It is for the first time that such experimental measurements have been reported for a free-standing InSb nanosheet and the results obtained indicate that InSb nanosheet/hBN/graphite gate structures can be used to develop advanced quantum devices for novel physics studies and for quantum technology applications.

Coulomb-dominated oscillations in a graphene quantum Hall Fabry–Pérot interferometer

The electronic Fabry–Pérot interferometer operating in the quantum Hall regime may be a promising tool for probing edge state interferences and studying the non-Abelian statistics of fractionally charged quasiparticles. Here we report on realizing a quantum Hall Fabry–Pérot interferometer based on monolayer graphene. We observe resistance oscillations as a function of perpendicular magnetic field and gate voltage both on the electron and hole sides. Their Coulomb-dominated origin is revealed by the positive(negative) slope of the constant phase lines in the plane of magnetic field and gate voltage on the electron(hole) side. Our work demonstrates that the graphene interferometer is feasible and paves the way for the studies of edge state interferences since high-Landau-level and even denominator fractional quantum Hall states have been found in graphene.

Intercalation of van der Waals layered materials: A route towards engineering of electron correlation

Being parent materials of two-dimensional (2D) crystals, van der Waals layered materials have received revived interest. In most 2D materials, the interaction between electrons is negligible. Introducing the interaction can give rise to a variety of exotic properties. Here, via intercalating a van der Waals layered compound VS2, we find evidence for electron correlation by extensive magnetic, thermal, electrical, and thermoelectric characterizations. The low temperature Sommerfeld coefficient is 64 mJ·K-2·mol-1 and the Kadowaki-Woods ratio rKW^0.20a0. Both supports an enhancement of the electron correlation. The temperature dependences of the resistivity and thermopower indicate an important role played by the Kondo effect. The Kondo temperature TK is estimated to be around 8 K. Our results suggest intercalation as a potential means to engineer the electron correlation in van der Waals materials, as well as 2D materials.

Low-thermal-budget synthesis of monolayer MoS_(2)

Two-dimensional(2D)materials,such as MoS_(2),have been considered as a competitive coordinate for future electronics due to their excellent electrostatics and high mobility[1-3].Moreover,the potential integration of 2D materials with silicon circuits can present increased density and multifunction in future heterogeneously integrated circuits[4,5].However,the high thermal-budget during MoS_(2) synthesis exceeds the temperature requirement of direct integration with Si in the back-end-of-line(BEOL)fabrication process[6-8].

Magnetoresistance hysteresis in topological Kondo insulator SmB6 nanowire

SmB6, a topological Kondo insulator, with a gapped bulk state and metallic surface state has aroused great research interest. Here, we report an exotic hysteresis behavior of magnetoresistance in individual SmB6 nanowire in a temperature range in which both surface and bulk states contribute to the total conductance. Under a magnetic field parallel to the SmB6 nanowire, the resistance suddenly increases at the turning point from up-sweep to down-sweep of the magnetic field. The magnetoresistance hysteresis loops are well consistent with the magnetocaloric effect. Our results suggest that the SmB6 nanowires possess potential applications in the magnetic cooling technology.