Ping Sheng

King Abdullah University of Science and Technology, Djidda, Makkah, Saudi Arabia

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Publications (314)1231.22 Total impact

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    ABSTRACT: We report new developments on the chemical vapor deposition growth of 0.4 nm single-walled carbon nanotubes (SWCNTs) inside the linear channels of the aluminophosphate zeolite, AlPO4-5 (AFI), single crystals (0.4 nm-SWCNT@AFI). Ethylene (C2H4) and carbon monoxide (CO) were used as the feedstock. Polarized Raman spectroscopy was used to analyze the structure and quality of SWCNTs, both the radial breathing mode and G-band are much clearer and stronger than the samples grown by the old process which used template tripropylamine molecules for growing SWCNT@AFI. From the Raman spectra, it is clearly seen that the RBM is composed of two peaks at 535 and 551 cm−1. By using the pseudopotential module in Material Studio to calculate the Raman lines, the 535 cm−1 peak is attributed to the (5,0) SWCNTs and the 551 cm−1 peak to the (3,3) SWCNTs. The abundance of (4,2) is relatively small. Thermal gravity analysis showed that while the samples grown by CO display less than 1 wt% of carbon, for the samples heated in C2H4 atmosphere the weight percentage of SWCNTs is around 10%, which implies ∼30% of the AFI channels are occupied with SWCNTs, a significant increase compared with the previous samples.
    Carbon 09/2014; 76:401–409. · 6.16 Impact Factor
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    ABSTRACT: The metal-insulator transition (MIT) is one of the remarkable electrical transport properties of atomically thin molybdenum disulphide (MoS2). Although the theory of electron-electron interactions has been used in modeling the MIT phenomena in MoS2, the underlying mechanism and detailed MIT process still remain largely unexplored. Here, we demonstrate that the vertical metal-insulator-semiconductor (MIS) heterostructures built from atomically thin MoS2 (monolayers and multilayers) are ideal capacitor structures for probing the electron states in MoS2. The vertical configuration of MIS heterostructures offers the added advantage of eliminating the influence of large impedance at the band tails and allows the observation of fully excited electron states near the surface of MoS2 over a wide excitation frequency (100 Hz-1 MHz) and temperature range (2 K- 300 K). By combining capacitance and transport measurements, we have observed a percolation-type MIT, driven by density inhomogeneities of electron states, in the vertical heterostructures built from monolayer and multilayer MoS2. In addition, the valence band of thin MoS2 layers and their intrinsic properties such as thickness-dependence screening abilities and band gap widths can be easily accessed and precisely determined through the vertical heterostructures.
    07/2014;
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    ABSTRACT: An impedance-matched surface has the property that an incident wave generates no reflection. Here we demonstrate that by using a simple construction, an acoustically reflecting surface can acquire hybrid resonances and becomes impedance-matched to airborne sound at tunable frequencies, such that no reflection is generated. Each resonant cell of the metasurface is deep-subwavelength in all its spatial dimensions, with its thickness less than the peak absorption wavelength by two orders of magnitude. As there can be no transmission, the impedance-matched acoustic wave is hence either completely absorbed at one or multiple frequencies, or converted into other form(s) of energy, such as an electrical current. A high acoustic-electrical energy conversion efficiency of 23% is achieved.
    Nature materials. 06/2014;
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    ABSTRACT: An impedance-matched surface has the property that an incident wave generates no reflection. Here we demonstrate that by using a simple construction, an acoustically reflecting surface can acquire hybrid resonances and becomes impedancematched to airborne sound at tunable frequencies, such that no reflection is generated. Each resonant cell of the metasurface is deep-subwavelength in all its spatial dimensions, with its thickness less than the peak absorption wavelength by two orders of magnitude. As there can be no transmission, the impedance-matched acoustic wave is hence either completely absorbed at one or multiple frequencies, or converted into other form(s) of energy, such as an electrical current. A high acoustic–electrical energy conversion e ciency of 23% is achieved.
    Nature Materials. 06/2014; 13.
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    Dataset: 1D goes 2D
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    ABSTRACT: We present a homogenization scheme for acoustic metamaterials that is based on reproducing the lowest orders of scattering amplitudes from a finite volume of metamaterials. This approach is noted to differ significantly from that of coherent potential approximation, which is based on adjusting the effective-medium parameters to minimize scatterings in the long-wavelength limit. With the aid of metamaterials' eigenstates, the effective parameters, such as mass density and elastic modulus can be obtained by matching the surface responses of a metamaterial's structural unit cell with a piece of homogenized material. From the Green's theorem applied to the exterior domain problem, matching the surface responses is noted to be the same as reproducing the scattering amplitudes. We verify our scheme by applying it to three different examples: a layered lattice, a two-dimensional hexagonal lattice, and a decorated-membrane system. It is shown that the predicted characteristics and wave fields agree almost exactly with numerical simulations and experiments and the scheme's validity is constrained by the number of dominant surface multipoles instead of the usual long-wavelength assumption. In particular, the validity extends to the full band in one dimension and to regimes near the boundaries of the Brillouin zone in two dimensions.
    Physical Review B 02/2014; 89:064309. · 3.66 Impact Factor
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    ABSTRACT: An acoustic/vibrational energy absorption metamaterial includes at least one enclosed planar frame with an elastic membrane attached having one or more rigid plates are attached. The rigid plates have asymmetric shapes, with a substantially straight edge at the attachment to said elastic membrane, so that the rigid plate establishes a cell having a predetermined mass. Vibrational motions of the structure contain a number of resonant modes with tunable resonant frequencies.
    Ref. No: US20140060962 A1, Year: 11/2013
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    ABSTRACT: We study theoretically and experimentally the nature of formation and properties of acoustic surface-guided modes (SGMs) at the interface of two phononic crystals (PCs). It is demonstrated that in the shared region of the frequency gaps, the SGMs can exist at the interface as a result of total reflections from both PCs, which causes the formation of nodal planes by the interference of the forward- and backward-propagating waves. The experiments show excellent agreement with the theory predictions.
    EPL (Europhysics Letters) 11/2013; 104(3):34005-. · 2.26 Impact Factor
  • Ping Sheng
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    ABSTRACT: We present a structurally and conceptually simple acoustic double negative metamaterial comprising two coupled membranes [Phys. Rev. Lett. 110, 134301 (2013)]. Owing to its symmetry, the system can generate both monopolar and dipolar resonances that are separately tunable, thereby making broadband double negativity possible. A homogenization scheme is implemented that enables the exact characterization of our metamaterial by the effective mass density and bulk modulus even beyond the usual long-wavelength regime, with the measured displacement fields on the sample's surfaces as inputs. Double negativity is achieved in the frequency range of 520-830 Hz. Transmission and reflection predictions using effective parameters are shown to agree remarkably well with the experiment. Work done in collaboration with M. Yang, G. C. Ma, and Z. Y. Yang.
    The Journal of the Acoustical Society of America 11/2013; 134(5):4026. · 1.65 Impact Factor
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    ABSTRACT: A device with simultaneous negative effective mass density and bulk modulus has at least one tubular section and front and back membranes sealing the tubular section. The front and back membranes sealing the tubular sections seal the tubular section sufficiently to establish a sealed or restricted enclosed fluid space defined by the tubular section and the membranes, and restrict escape or intake of fluid resulting from acoustic vibrations. A pair of platelets are mounted to the membranes, with the individual platelets substantially centered on respective ones of the front and back membranes.
    Ref. No: US20140116802 A1, Year: 10/2013
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    Ting Zhang, Ping Sheng
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    ABSTRACT: By using two-loop renormalization group analysis, we explore the phase diagram with respect to the electron–phonon and Coulomb interaction strengths in the two (3,3)@(8,8) and (5,0)@(15,0) double-wall carbon nanotube systems (DWCNTs). Using estimation of the two types of coupling strengths from ab initio calculations, both systems are shown to scale to the superconducting fixed point as temperature decreases to zero. This is in contrast to the (3,3) and (5,0) single-wall carbon nanotubes, which scales to the Peierls-distorted semiconducting ground state. While the superconducting transition temperature can be quite low in the (3,3)@(8,8) system, the (5,0)@(15,0) promises observable superconducting behavior. Our result is in support of recent experimental observation of superconductivity in DWCNTs.
    New Journal of Physics 08/2013; 15(8):083021. · 4.06 Impact Factor
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    ABSTRACT: We report a direct measurement of the friction coefficient of a fluctuating (and slipping) contact line using a thin vertical glass fiber of diameter d with one end glued onto a cantilever beam and the other end touching a liquid-air interface. By measuring the broadening of the resonant peak of the cantilever system with varying liquid viscosity η, we find the friction coefficient of the contact line has a universal form, ξ_{c}≃0.8πdη, independent of the liquid-solid contact angle. The obtained scaling law is further supported by the numerical simulation based on the phase field model under the generalized Navier boundary conditions.
    Physical Review Letters 07/2013; 111(2):026101. · 7.73 Impact Factor
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    ABSTRACT: Conventional means of attenuating airborne sound usually require blocking the air medium with a solid material. By exploiting properties of membrane-type acoustic metamaterials (MAMs), we demonstrate large transmission loss to be achievable across a sizable orifice through which air can freely flow. We find that interaction of resonating field of the MAMs with the continuous sound field passing through the orifice is responsible for such phenomenon. The narrow-band characteristic of this effect can be used for acoustic filtering of noise with a particular narrow frequency band.
    Applied Physics Letters 07/2013; 103(1). · 3.52 Impact Factor
  • Physical Review Letters 05/2013; 110(20). · 7.73 Impact Factor
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    ABSTRACT: We demonstrate that fluctuations of the local density of states (LDOS) in strongly disordered graphene play an important role in determining the quantum capacitance of the top-gate graphene devices. Depending on the strength of the disorder induced by metal-cluster decoration, the measured quantum capacitance of disordered graphene can dramatically decrease in comparison with pristine graphene. This is opposite to the common belief that quantum capacitance should increase with disorder. To explain this counterintuitive behavior, we present a two-parameter model which incorporates both the non-universal power law behavior for the ADOS and a lognormal distribution of LDOS. We find excellent quantitative agreements between the model and measured quantum capacitance for three disordered samples in a wide range of Fermi energies. Thus, by measuring the quantum capacitance, we can simultaneously determine the ADOS and its fluctuations. It is the LDOS fluctuations that cause the dramatic reduction of the quantum capacitance.
    Scientific Reports 05/2013; 3:1772. · 5.08 Impact Factor
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    ABSTRACT: Over the past decade, the emergence of acoustic metamaterials has considerably broadened the possibility of acoustic wave manipulations. Within this area, exotic effective constitutive parameters (mass density and bulk modulus) are a most hotly pursued topic, at the core of which is the realization of acoustic double negativity. Here, we show with experiments, simulations and homogenization that a single resonant structure can achieve acoustic double negativity. The metamaterial is comprised of two decorated elastic membranes, which are connected together by a rigid ring. Impedance measurement reveals that the system's transport behavior is governed by the three eigenmode resonances in the sub-kHz regime, which are separately tunable via system parameters. Measured displacement profiles at the sample surfaces using laser vibrometer show that the system's eigenmodes are, respectively, dipolar or monopolar in their nature. The simplicity of the metamaterial also enables us to retrieve its effective mass density and effective bulk modulus by performing homogenization. The results help explaining the physics behind the transport properties, and confirm that a double-negative passband is realized in a frequency range (around 500-800 Hz). Excellent agreement between experiments, simulations, and theory is achieved.
    The Journal of the Acoustical Society of America 05/2013; 133(5):3431. · 1.65 Impact Factor
  • Min Yang, Zhiyu Yang, Ping Sheng
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    ABSTRACT: Metamaterials extend the realm of materials' properties by carefully designed structural inclusions. By targeting the extraction of effective properties from composite materials, homogenization theory plays an important role for metamaterials in their design and characterization. However, conventional homogenization methods are limited to the long wavelength limit. Here, we introduce an exact homogenization scheme valid for one-dimensional metamaterials over the full frequency band. In this scheme, with the aid of eigenstates' characterization, a set of explicit formulas for effective mass density and effective elastic modulus are obtained by matching the surface responses properties of a metamaterial's single structural unit with a piece of effectively homogenized material. In the frequency regimes beyond the conventional homogenization theory, new features, such as the imaginary parts of the effective parameters, have been found. Applying this scheme on a layered structure, the predicted transport properties and displacement fields from the effective parameters show excellent agreement with numerical simulations.
    The Journal of the Acoustical Society of America 05/2013; 133(5):3289. · 1.65 Impact Factor
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    ABSTRACT: We have produced ultra-thin lead (Pb) nanowires in the 6 nm pores of SBA-15 mesoporous silica substrates by chemical vapor deposition. The nanowires form regular and dense arrays. We demonstrate that bulk Pb (a type I superconductor below Tc = 7.2 K with a critical field of 800 Oe) can be tailored by nanostructuring to become a type II superconductor with an upper critical field (Hc2) exceeding 15 T and signs of Cooper pairing 3 - 4 K above the bulk Tc. The material undergoes a crossover from a one-dimensional (1D) fluctuating superconducting state at high temperatures to a three-dimensional (3D) long-range-ordered superconductivity in the low temperature regime. We show with our data in an impressive way that superconductivity in elemental metals can be greatly enhanced by nanostructuring.
    ACS Nano 04/2013; · 12.03 Impact Factor
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    [Show abstract] [Hide abstract]
    ABSTRACT: We present a structurally and conceptually simple acoustic double negative metamaterial comprising two coupled membranes. Owing to its symmetry, the system can generate both monopolar and dipolar resonances that are separately tunable, thereby making broadband double negativity possible. A homogenization scheme is implemented that enables the exact characterization of our metamaterial by the effective mass density and bulk modulus even beyond the usual long-wavelength regime, with the measured displacement fields on the sample's surfaces as inputs. Double negativity is achieved in the frequency range of 520-830 Hz. Transmission and reflection predictions using effective parameters are shown to agree remarkably well with the experiment.
    Physical Review Letters 03/2013; 110(13):134301. · 7.73 Impact Factor
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    ABSTRACT: Through exponential sample-size scaling of conductance, we demonstrate strong electron localization in three sets of nanostructured antidot graphene samples with localization lengths of 1.1, 2, and 3.4 μm. The large-scale mesoscopic transport is manifest as a parallel conduction channel to 2D variable range hopping, with a Coulomb quasigap around the Fermi level. The opening of the correlation quasigap, observable below 25 K through the temperature dependence of conductance, makes possible the exponential suppression of inelastic electron-electron scatterings and thereby leads to an observed dephasing length of 10 μm.
    Physical Review Letters 02/2013; 110(6):066805. · 7.73 Impact Factor

Publication Stats

6k Citations
1,231.22 Total Impact Points

Institutions

  • 2014
    • King Abdullah University of Science and Technology
      • Division of Computer, Electrical and Mathematical Sciences and Engineering (CEMSE)
      Djidda, Makkah, Saudi Arabia
  • 1970–2014
    • The Hong Kong University of Science and Technology
      • • Department of Physics
      • • Department of Mathematics
      Chiu-lung, Kowloon City, Hong Kong
  • 2003–2013
    • Nano Science and Technology Institute
      Austin, Texas, United States
    • Nanjing University
      • Department of Physics
      Nanjing, Jiangsu Sheng, China
  • 2012
    • South China University of Technology
      Shengcheng, Guangdong, China
  • 2010
    • Soochow University (PRC)
      • School of Physical Science and Technology School of Energy
      Suzhou, Jiangsu Sheng, China
  • 2006–2010
    • Wuhan University
      • Department of Physics
      Wuhan, Hubei, China
  • 2004
    • University of Toronto
      Toronto, Ontario, Canada
  • 1997–2004
    • University of Manitoba
      • Department of Physics and Astronomy
      Winnipeg, Manitoba, Canada
    • The Chinese University of Hong Kong
      • Department of Physics
      Hong Kong, Hong Kong