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Theoretical Exposition of A Single Electron Quantum Dot T. Cahyanto, Wahyu; Abraha, Kamsul; Nurwantoro, Pekik
IPTEK The Journal for Technology and Science Vol 18, No 2 (2007)
Publisher : Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (348.872 KB) | DOI: 10.12962/j20882033.v18i2.174

Abstract

This paper will review atomic-like phenomena in a semiconductor quantum dot which their size, shape and interactions can be precisely controlled through the use of nanofabrication technology. It has been shown that by confining electrons in three dimensions inside semiconductors, quantum dots can show many of the phenomena observed in atoms and nuclei and so called artificial atom. Because of its controlable system, it is possible to explore the correlation effects in regimes that cannot otherwise be accessed in other physical systems. For simplicity, this work will focus on a circular-shape single electron quantum dot trapped by polar two-dimensional harmonic potential in the presence of an external magnetic field. Both Zeeman splitting and spin orbit interaction are neglected in our calculation. The calculation show that Fock-Darwin spectrum will enter Landau regime, where when cyclotron frequency is much larger than potential confinement .
Penyempitan Lebar Garis Spektral Keluaran Laser Zatwarna Pulsa Dengan Pasangan-Pasangan Prisma Maruto, Guntur; Kusminarto, Kusminarto; Hermanto, Arief; Nurwantoro, Pekik
Berkala Ilmiah MIPA Vol 23, No 1 (2013)
Publisher : FMIPA UGM

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Abstract

Penelitian untuk penyempitan garis spektral luaran berkas laser zatwarna dipaparkan dalam paper ini. Untuk mengamati secara langsung garis spektralnya, berkas laser didispersikan oleh kisi pantul di dalam wavelength-meter dan dilihat dari mikroskop pada wavelength-meter. Lebar garis spektral dapat diketahui dengan pertolongan garis-garis skala di dalam wavelength-meter. Spektrum berkas laser yang terlihat dari mikroskop dipotret untuk dapat dan mudah diperlihatkan dalam bentuk foto. Upaya untuk mempersempit lebar garis spektral luaran berkas laser dilakukan dengan menempatkan pasangan prisma-prisma di dalam resonator optik unit laser. Dengan menempatkan 2 pasang prisma telah diperoleh penyempitan garis spektral dengan faktor sekitar 1/30. Hasil penyempitan garis spektral luaran berkas laser telah diuji dengan menggunakan berkas laser tersebut dalam Sistem Spektroskopi Laser-Berkas Atom untuk mengamati garis-garis D1 dan D2 pada atom natrium (Na). Dari uji spektroskopi ini efek penyempitan garis spektral berkas laser terlihat dengan jelas
TELAAH TEORITIS BAK-ATOM QUANTUM DOT SEMIKONDUKTOR DALAM MEDAN MAGNET LUAR Cahyanto, Wahyu Tri; Abraha, Kamsul; Nurwantoro, Pekik
Berkala Ilmiah MIPA Vol 16, No 3 (2006)
Publisher : FMIPA UGM

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Abstract

Analytical calculation on the atomic-like phenomena is presented in a semiconductor quantum dot trapped by two-dimensional harmonic potential in the presence of a homogeneous magnetic field. The calculation neglects both Zeeman splitting and spin orbit interaction. This paper is proposed as the first sight of advanced research on nanotechnology in Indonesia. Many of the phenomena observed in atoms and nuclei are also observed in the semiconductor quantum dot which is then called an artificial atom. It has been shown that atomic shells can be described by a set of degenerated energy levels filled by 2, 6, 12, ... electrons known as “magic numbers”. The results of the calculations show that the Fock-Darwin spectrum will enter Landau regime when its cyclotron frequency (fc) is much larger than the frequency associated with the potential confinement (fo). Keywords: Semiconductor quantum dot, Electron confinement, Shell structure, Artificial atom
Density-Functional-Theory Calculations of Formation Energy of the Nitrogen-Doped Diamond Sholihun, Sholihun; Kadarisman, Hana Pratiwi; Nurwantoro, Pekik
Indonesian Journal of Chemistry Vol 18, No 4 (2018)
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (479.137 KB) | DOI: 10.22146/ijc.26785

Abstract

The geometry optimization of the nitrogen-doped diamond has been carried out by the density functional theory (DFT) calculations. We model the defective diamond of substitutional and interstitial nitrogen atoms by using a simple-cubic supercell. Atoms in the supercell are relaxed by allowing them to move so that the atomic forces are less than 5.0 × 10-3 eV/Å. We calculate the formation energy for substitutional and interstitial sites. We find that the formation energy for the substitutional defect is10.89 eV. We check the convergence of the calculation with respect to the k×k×k - Monkhorst-Pack grids. We show that the energy difference between k = 4 and 6 is very small (7.0 meV). We also check the calculations by using a 216-sites supercell and find that the energy difference is 0.10 eV. Thus, the calculations of the formation energy converge well. As for the interstitial defect, we model some possible configurations and find that the smallest formation energy is 21.88 eV. Therefore, the most stable configuration of the nitrogen-doped diamond belongs to the substitutional site.
Introducing Undergraduate Students to Nonlinear Dynamics through A Numerical Approach Nugroho, Fahrudin; Azhari, Irfan Taufiq; Yusuf, Yusril; Nurwantoro, Pekik
Omega: Jurnal Fisika dan Pendidikan Fisika Vol 4 No 2 (2018)
Publisher : Program Studi Pendidikan Fisika UHAMKA

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31758/OmegaJPhysPhysEduc.v4i2.45

Abstract

This paper describes a numerical method that used to solve the nonlinear Schr\"{o}dinger equation. The methods are an exponential time differencing method and a spectral method. The result indicates that at a certain parameter, fluctuation of wave function has contained chaotic dynamics. This case is expected to be used as an example for introducing numerical methods to undergraduate students on nonlinear dynamics. This introduction is deemed necessary, referring to the curriculum and syllabus used in several educational institutions in various countries that have included the topic of nonlinearity.
Simulasi Komputer Pengaruh Efek Proksimitas pada Medan Kritis Superkonduktor Anwar, Fuad; Nurwantoro, Pekik; Hermanto, Arief
Risalah Fisika Vol 1, No 2 (2017): Risalah Fisika ISSN 2548-9011
Publisher : Physical Society of Indonesia (PSI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (368.304 KB) | DOI: 10.35895/rf.v1i2.21

Abstract

Telah dibuat kajian pengaruh syarat batas efek proksimitas pada penyelesaian komputasi persamaan Ginzburg-Landau Gayut Waktu. Bahan kajian adalah superkonduktor berbentuk kotak yang berbatasan dengan bahan lain pada keempat sisinya dan dipengaruhi medan magnet luar. Metode pembuatan simulasi didasarkan pada persamaan Ginzburg-Landau gayut waktu serta persamaan syarat batas parameter benahan dan syarat batas medan magnet. Persamaan-persamaan tersebut lalu didiskretkan dengan menggunakan metode yU. Hasil kajian menunjukkan bahwa nilai medan kritis permukaan membesar, medan kritis rendah mengecil pada ukuran bahan Nx×Ny = 12×12 dan membesar pada ukuran bahan Nx×Ny = 32×32 jika nilai panjang ekstrapolasi membesar. Kata kunci: efek proksimitas, persamaan TDGL, superkonduktor