Research area of school of Physics Research area of school of Physics

 

Research area of school of Physics

Atomic & Molecular Physics

 

Atomic and Molecular division of Department of Physics  has currently 5 full-time and one retired faculty members:

 

  • Aghamir, Farzin M. (Professor)
  • Ghorbanzadeh, Atamalek (Associate Professor)
  • Hassani, Khosrow (Assistant Professor)
  • Koohian, Ataollah (Associate Professor)
  • Nahal, Arashmid (Associate Professor)
  • Tavassoly, Mohammad Taghi (Retired Professor)

 

Light and its interaction with matter is, perhaps, the most adequate term to describe the broad research areas in our group. Depending on the academic background and personal interest, people in our group look at this subject from their own perspective and with their favorite techniques. Some of the major topics currently investigated in our group, are summarized as follows:

 

    Optical Diffractometry: The quantitative treatment of Fresnel diffraction, a well known topic in classical optics, has proved to be a promising technique with many novel applications to measure literally any phenomenon that can cause abrupt changes in light amplitude, phase, or even polarization. This new emerging technique which has mainly developed by Prof. Tavassoly and his co-workers, is currently used by him, Dr. Hassani, and their students to measure thin film thickness and nanometer displacements with a few nanometer resolution, refractive index of solids and liquids with high precision, optical constants of metal layers, and spectroscopy of relatively wide spectrum sources with great precision..

    Interaction of Light with Metallic Nanoparticles: As a results of  interaction of laser beam with silver-ion-exchanged glasses reduction of ionic clusters occurs  and, at the same time, produced neutral clusters aggregate and form nanoparticles. During this interaction fluorescence spectra of the samples changes, indicating the resizing and changes in the interaction of nanoparticles with their matrix. Interaction of the focused high power laser beam results in formation of fractal structures made from the silver nanoparticles. Simultaneous heating and exerting external uniform electric field parallel to the surface of the samples result in arrangement of the produced neutral nanoparticles along the field, which makes them dichroic photonic materials. Dr. Nahal and his team study these phenomena, extensively.

    Moiré Technique, including Moiré interferometry, and metrology:

    Moiré technique is a very powerful and relatively simple optical method with several fascinating applications. This technique has been studied and applied, mainly by Prof. Tavassoly and his co-workers, to solve various problems, including the measurement of refractive index, atmosphere turbulence, and Optical Transfer Function (OTF), just to mention a few. Please, refer to the publication list of our group for more exact information. Prof. Tavassoly believes that the capabilities of this technique has not yet fully exploited and there is still plenty of space to work on this phenomenon. Moire measurements have a fairly rich tradition in Prof. Tavassoly's research.

    Laser-induced Properties in Light-Sensitive Thin Films: Interaction of laser beam with thin AgCl films doped by Ag nanoparticles, results in excitation of waveguide modes of the thin AgCl film and consequently interference of the excited mode with the incident  beam. Silver nano-clusters move into the minima of the interference pattern, which results in formation of Spontaneous Periodic Structures in the AgCl-Ag film. The shape of the produced gratings depends on the polarization state of the incident beam. Dr. Nahal and his students are actively pursuing this field, as well.

    Dynamic Light Scattering:  If coherent light is incident on a sample containing moving or evolving elements, the light scattered from nearby particles can interfere and produce low or high intensity signals. Some of the static (e.g. particle sizes and distributions) or dynamic (Diffusion constant, flow rate, speed, etc.) of sample particles under study can be extracted from the statistical analysis of the scattered light intensity. If each photon on average scatters only once, this technique is traditionally known as Dynamic Light Scattering (DLS) or Photon Correlation Spectroscopy (PCS). If, however, photons get the chance to scatter many times before leaving the sample, the information regarding the initial direction of the incident photons is lost and photons behave, more or less, like small particles undergoing diffusion in a fluid. If an extended light detector (such as a CCD camera) is used in front of the scattered light, random areas of constructive interference (known as speckles) form. Again, the dynamical properties of the scatterers in the sample can be inferred from careful analysis of these speckle patterns. This multi-scattering regime, depending on the details of the measurement, is known as Diffusing Wave Spectroscopy (DWS) or Speckle Visibility Spectroscopy (SVS).  Dynamic light scattering techniques have got many applications in soft condensed matter physics and biology. Dr. Hassani in collaboration with Dr. Miri (from the Condensed Matter group) try to apply some of these techniques to the samples of interest.

 

 

 

Condensed Matter & Nano Physics

 

Condensed matter physics aims to discover the properties of matter in its condensed phases and understand them from fundamental principles of quantum mechanics, electromagnetism, and statistical mechanics.

 

The Condensed Matter Group at University of Tehran is carrying out research in a broad range of areas of experimental, theoretical, and computational physics. The main research subjects in our group are:

 

Experimental physics:

 

  • Nanophysics (Carbon nanotubes, Graphene, Nano-devices, Gas sensors, Solar cells, Nanoparticles)
  • Surface science (Thin films, Hetro-structures, Nano-porous films, Self-clean glasses,  Nano-sculptured thin films, Surface plasmonics, Corrosion, Photonic crystals, Modification, mechanical, & tribological effects, hydrophobocity)
  • Superconductivity (Bulk and Thin films)

 

Theoretical physics:

 

  • Bio-physics and complex systems (Tumor Growth, Networks)
  • Computational physics (Molecular dynamics, Density functional theory, Quantum Monte Carlo simulations)
  • Disordered systems (Wave propagation in random media, Anderson localization, Transport in random media, Stochastic processes)
  • Nanophysics (Nano-machines, Optics of nanostructures)
  • Soft matter (Foam, Granular matter)
  • Statistical physics (Growth models, Fractals, Fluctuation induced interactions, Spin systems)
  • Surface science (Sculptured thin films)

 

The group has access to extensive experimental and computational facilities, in particular, physical and chemical vapor deposition systems, morphological and structural analysis facilities (AFM, STM, XRD), optical characterization systems (UV-visible photo-spectrometer, Ellipsometery), GPU computing, and a 56-core clusters.

 

This division currently consists of 8 full-time faculty members:

 

  • Abdi, Yaser (Assistant Professor)
  • Arzi, Ezatollah (Professor)
  • Miri, Mirfaez (Assistant Professor)
  • Mohammadizadeh, Mohammad Reza (Associate Professor)
  • Saberi, Abbas Ali (Assistant Professor)
  • Savaloni, Hadi (Professor)
  • Sepehrinia, Reza (Assistant Professor)
  • Vaez Allaei, Seyed Mehdi (Assistant Professor)

 

 

Elementary Particle Physics

 

Research Areas:

 

    Structure function of hadrons and nuclei, EMC effect, Perturbative and nonperturbative quantum chromodynamics, Quark-gluon plasma, Gluon fusion contribution in Higgs boson cross section, Calculation of parton functions corresponding to transverse momentum and their roles in production of heavy mesons.

    Many particle systems in strong interaction and short range.

    Field theory and particle Physics in curved space time, Early universe, Dark energy, Dark matter.

    Topological effects in Particle Physics.

    The idea of holography (gauge/gravity duality) and its applications in the strongly coupled theories, most importantly, QCD and QGP (Quark-Gluon Plasma).

    Studying QCD vacuum by topological defects like monopoles and dyons and center vortices,QCD and lattice gauge theory, Using phenomenological models to study quark confinement and calculating the potential between quarks.

 

 

 

Faculty members:

  • Deldar, Sedigheh (Associate Professor)
  • Ebrahim Najafabadi, Hajar (Assistant Professor)
  • Modarres, Majid (Professor)
  • Mohseni Sajadi, Hossein (Associate Professor)

 

Gravitation & Astrophysics

 

The Gravitation and Astrophysics division  has 6 faculty members:

  • Abbasi, Amir Masoud (Associate Professor)
  • Ahmadi, Nahid (Assistant Professor)
  • Noorbala, Mahdiyar (Assistant Professor)
  • Nouri-Zonoz, Mohammad (Associate Professor)
  • Shojai Baghini, Ali (Associate Professor)
  • Shojai Baghini, Fatimah (Associate Professor)

 

Research in our group is conducted on theoretical topics that are, in one way or another, related to Einstein's general theory of relativity (GR). From attempts to better understand GR by studying various phenomena, to investigations of modified theories of gravity. Cosmology and astrophysics are also arenas for applications of GR: from very early universe to the late time epochs. The diversity of these activities grow even further, when combined with developments in particle physics or speculative ideas of quantum gravity.

 

For more information please refer to the individual faculty pages.

 

 

Nuclear Physics

 

Strong and weak are two forces of four fundamental interactions in the nature. Therefore the studies of these forces are one of the main objects of science of physics. In this respect the nuclear physics is intriguing and interesting subject where with the help of theoretical models and experimental achievements one could be able  to study the big bang primary and predominant reactions and production of light nuclei, structure of heavy nuclei in the nature, complexity of forces between  particles materialized nucleus, formation and structure of stars.

In this study the classical and quantum mechanical theories as well as experimental technology are incorporated. In fact it is not exaggerated if one assumes that the nucleus and related systems are an experimental testing ground for correctness of the fundamental physics.

Members of the nuclear group of this faculty  have lectured  in addition to different subjects of physics they also have addressed the nuclear physics and related subjects in BSc, MSc and PhD levels. Many students in MSc and PhD levels have been participating in different projects with members of this group during years.

The research area and subjects of thesis for MSc and PhD are:

  • Nuclear Structure Theory
  • Analysis and Study of Forces
  • Nuclear Matter and Neutron stars
  • Determination and Calculation of Structure Function of Hadrons Specifically Nucleon
  • Accelerators and Related Subjects
  • Pion less Effective Field Theory and Few-Body System
  • Pion full CPT (Chiral Perturbation Theory) and Few- Body System
  • LQCD (Lattice Quantum Chromodynamics)  and Few -Body System

 

The members of this group are:

 

  • S.Bayegan (Professor)

 

Also we have the collaboration of Professor M.Modarres from Elementary Particle group.