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Search Results: 1 - 10 of 89 matches for " Argo Nurbawono "
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Sensing with Superconducting Point Contacts
Argo Nurbawono,Chun Zhang
Sensors , 2012, DOI: 10.3390/s120506049
Abstract: Superconducting point contacts have been used for measuring magnetic polarizations, identifying magnetic impurities, electronic structures, and even the vibrational modes of small molecules. Due to intrinsically small energy scale in the subgap structures of the supercurrent determined by the size of the superconducting energy gap, superconductors provide ultrahigh sensitivities for high resolution spectroscopies. The so-called Andreev reflection process between normal metal and superconductor carries complex and rich information which can be utilized as powerful sensor when fully exploited. In this review, we would discuss recent experimental and theoretical developments in the supercurrent transport through superconducting point contacts and their relevance to sensing applications, and we would highlight their current issues and potentials. A true utilization of the method based on Andreev reflection analysis opens up possibilities for a new class of ultrasensitive sensors.
Reversible magnetism switching in graphene-based systems via the decoration of photochromic molecules
Argo Nurbawono,Chun Zhang
Physics , 2013, DOI: 10.1063/1.4831742
Abstract: By first principles calculations, we demonstrate that when decorated with photochromic molecules, it is possible to use light to reversibly control the magnetic properties of a nanoscale magnetic system. The combination of a graphene-based magnetic system and a photochromic azobenzene molecule is chosen as a model system. The {\it trans} and {\it cis} isomers of the azobenzene molecule that can be converted between each other by means of photoexcitations are found to have drastically different effects on the magnetic properties of the system. The results may pave the way for the future design of light controllable molecular-scale spintronic devices.
Electron tunneling through hybrid superconducting-normal quantum point contacts under microwave radiation
Argo Nurbawono,Yuan Ping Feng,Chun Zhang
Physics , 2009, DOI: 10.1103/PhysRevB.82.014535
Abstract: We present a theoretical analysis for photon-assisted electron tunneling through a hybrid superconducting-normal quantum point contact (QPC) consisting of a superconducting lead (S), a normal two-level quantum dot (N), and a normal lead (N). Using single particle non-equilibrium Green's function formalism, we incorporate Floquet basis in the Nambu space and solve the Green's function with finite matrix truncation to obtain the transport properties numerically. Based on the proposed method, we studied the effects of photon-induced single-level oscillations and quantum transition between two levels on the current-voltage (I-V) characteristics of a superconducting QPC. For the single level case, the main dc resonance in the I-V curve remains unchanged regardless of the frequency and amplitude of the radiation, and a series of secondary resonances due to multi-photon processes are present. When the transition between two levels ($\epsilon_{1}$, $\epsilon_{2}$) is taken into account and level oscillations are neglected, photons only have significant effects at Rabi resonance when $\hbar\omega=(\epsilon_{2}-\epsilon_{1})$. At Rabi resonance, the main dc resonance splits into two, and the separation between them is determined by the coupling strength of the two levels.
Manipulating absorption and diffusion of H atom on graphene by mechanical strain
Ming Yang,Argo Nurbawono,Chun Zhang,Rongqin Wu
AIP Advances , 2011, DOI: 10.1063/1.3622614
Abstract: Effects of the tensile strain on absorption and diffusion of hydrogen atoms on graphene have been studied by first-principles calculations. Our calculations suggested that there exists a barrier of 0.22 eV for H atom to diffuse from free space to graphene. The barrier originates from the transition of the hybridization of the H-binded carbon atom in graphene from sp2 to sp3, and is robust against the tensile strain. It was also found that, first, the in-plane diffusion of H atoms on graphene is unlikely to happen at low temperature due to the high barrier without or with strain, and second, the tensile strain along the armchair direction greatly decreases the out-plane diffusion barrier of H atoms, making it possible at low temperature. In particular, when the armchair strain is moderate (<10%), we found that the out-plane diffusion of H atoms likely to happen by diffusing through C-C bonds, and for relatively large armchair strain around 15%, the out-plane diffusion will happen though the center of the benzene ring.
Two-dimensional Graphene Superlattice Made with Partial Hydrogenation
Ming Yang,Argo Nurbawono,Chun Zhang,Ariando,Yuan Ping Feng
Physics , 2010, DOI: 10.1063/1.3425664
Abstract: Electronic properties of two-dimensional graphene superlattice made with partial hydrogenation were thoroughly studied via Density Functional Tight Binding approach (DFTB) which incorporates the tight-binding method into the density functional formalism. The two-dimensional (2-d) pattern of hydrogen atoms on graphene was found to have great effects on electronic structures of graphene superlattice. In particular, the edges of the 2-d pattern, armchair or zigzag, are essential for the energy band gap opening, and the energy band gap sensitively depends on the shape, size, and the 2-d periodicity of the pattern. Based on these findings, we suggested that the 2-d graphene superlattice may be used in fabricating quantum dots and 2-d heterojunctions on graphene without the need for cutting or etching.
Differential Conductance Anomaly in Superconducting Quantum Point Contacts
Argo Nurbawono,Yuan Ping Feng,Erhai Zhao,Chun Zhang
Physics , 2009, DOI: 10.1103/PhysRevB.80.184516
Abstract: We present in this letter a theoretical analysis of the current-voltage (I-V) characteristics of a hybrid normal-superconducting device consisting of a quantum dot and two electrodes that can be either normal or superconducting. We show that voltage drops at two different contacts that have been regarded unimportant in literature play essential roles in the Andreev tunneling process when at least one of electrodes is superconducting. A differential-conductance-anomaly caused by the aforementioned voltage drops is predicted. We also propose a new spectroscopy method to measure the energy levels of a quantum dot as well as voltage drops at contacts between the quantum dot and the two leads. Our findings have potential applications for the next generation of electronic devices at nanoscale.
Massless Dirac Fermions in Graphene under an External Periodic Magnetic Field
Shuanglong Liu,Argo Nurbawono,Na Guo,Chun Zhang
Physics , 2013, DOI: 10.1088/0953-8984/25/39/395302
Abstract: By solving two-component spinor equation for massless Dirac Fermions, we show that graphene under a periodic external magnetic field exhibits a unique energy spectrum: At low energies, Dirac Fermions are localized inside the magnetic region with discrete Landau energy levels, while at higher energies, Dirac Fermions are mainly found in non-magnetic regions with continuous energy bands originating from wavefunctions analogous to particle-in-box states of electrons. These findings offer a new methodology for the control and tuning of massless Dirac Fermions in graphene.
About Attitudes towards Death in the Light of Psychology
Argo Moor
Folklore : Electronic Journal of Folklore , 2004,
Abstract: The article observes death-consciousness of contemporary people. The decrease of the transcendence thematic in culture is a probable decrease of death thematic. At the same time unfinished grief causes depression and malfunctions. The loss of someone close will always be dramatic, but is the acceptance of our own mortality agreeing with the finality of our own lives? We could outline several criteria as relationships with relatives, life's significance, health which are connected with the the principle that one's death and afterlife correspond to the life they have lived.
Awareness of Death: A Controllable Process or a Traumatic Experience?
Argo Moor
Folklore : Electronic Journal of Folklore , 2002,
Abstract: We do not know what comes after death. But as human beings, aware of our mortality, we inevitably relate ourselves to our mortality. One output of such relating includes various beliefs about how the life of a person, his/her death and after-death existence are connected. Different beliefs have different ethical consequences and different impact on life. The beliefs do not have a direct influence, but they presume the actualisation of awareness of death. This paper shall focus on the conditions of such actualisation and describes the accompanying phenomena. It is shown how, depending on environmental, cultural-ideological and personal qualities, people may become aware of death either in a relatively harmonic way or it may be a traumatic experience.
The e-MERLIN Data Reduction Pipeline
Megan Argo
Physics , 2015, DOI: 10.5334/jors.bp
Abstract: Written in Python and utilising ParselTongue to interface with the Astronomical Image Processing System (AIPS), the e-MERLIN data reduction pipeline is intended to automate the procedures required in processing and calibrating radio astronomy data from the e-MERLIN correlator. Driven by a plain text file of input parameters, the pipeline is modular and can be run in stages by the user, depending on requirements. The software includes options to load raw data, average in time and/or frequency, flag known sources of interference, flag more comprehensively with SERPent, carry out some or all of the calibration procedures including self-calibration), and image in either normal or wide-field mode. It also optionally produces a number of useful diagnostic plots at various stages so that the quality of the data can be assessed. The software is available for download from the e-MERLIN website or via Github.
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