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S. Ahmad Ketabi

Dean of School of Physics and Professor of Condensed Matter Physics

Education

  • Ph.D. 1997-2002

    Theoretical Condensed Matter Physics

    Thesis: The Properties of Electron Transport in π - Conjugated Polymers

    Supervisor: Prof. N. Shahtahmasebi

    Ferdowsi University of Mashhad, Mashhad, Iran

  • M.Sc. 1992-1995

    Solid States Physics

    Thesis: Vibrational and thermal properties of 3-dimentional disordered systems

    Supervisor:  Prof. N. Shahtahmasebi

    Teacher Training University, Tehran, Iran

  • B.Sc. 1988-1992

    Physics

    Project:  Determination of Miller Indices: Rotational Crystal Method
    Supervisor: Prof. N. Tajabor

    Subject Class: Solid States Physics

    Ferdowsi University of Mashhad, Mashhad, Iran

Teaching

  • Condensed Matter Physics (Enz)
  • Classical Mechanics I and II (Symon and Goldstein)
  • Electromagnetism (Reitz and Milford)
  • Electrodynamics (Jackson)
  • Advanced Quantum Physics (Sakurai)
  • Advanced Solid State Physics (Ashcraft and Mermin)
  • Advanced Statistical Mechanics and thermodynamics (Pathria)
  • Mathematical Methods for Physicists (Arfken)
  • Programming in Fortran 90 and MatLab

Selected Publications

Nakhaee, M., Ketabi, S.A., Peeters, F.M. Dirac nodal line in bilayer borophene: Tight-binding model and low-energy effective Hamiltonian (2018) 98 (11), art. no. 115413, .

DOI: 10.1103/PhysRevB.98.115413

Bilayer hexagonal borophene, which is bound together through pillars, is a novel topological semimetal. Using density functional theory, we investigate its electronic band structure and show that it is a Dirac material which exhibits a nodal line. A tight-binding model was constructed based on the Slater-Koster approach, which accurately models the electronic spectrum. We constructed an effective four-band model Hamiltonian to describe the spectrum near the nodal line. This Hamiltonian can be used as a new platform to study the new properties of nodal line semimetals. We found that the nodal line is created by edge states and is very robust against perturbations and impurities. Breaking symmetries can split the nodal line, but cannot open a gap. © 2018 American Physical Society.

PUBLISHER: American Physical Society


Pourhassan, B., Faizal, M., Ketabi, S.A. Logarithmic correction of the BTZ black hole and adaptive model of graphene (2018) 27 (12), art. no. 1850118, .

DOI: 10.1142/S0218271818501183

It is known that almost all approaches to quantum gravity produce a logarithmic correction term to the entropy of a black hole, but the exact coefficient of such a term varies between the different approach to quantum gravity. Such logarithmic terms can also occur due to thermal fluctuations in both analogous and real black holes so that we will analyze the effects of logarithmic corrections term with variable coefficient on properties of analogous black hole. As these properties can be experimentally tested, they can be used to obtain the correct coefficient for such terms for an analogous black hole. We will argue that as even the real black holes can be considered as thermodynamical objects in Jacobson formalism, so such analogous black holes can be used to obtain the correct coefficient for the real black holes, and this in turn can be used to select the correct approach to quantum gravity. In that case, we use an adaptive model of graphene, which is still far from real graphene, to investigate some thermodynamics quantities of BTZ black hole. © 2018 World Scientific Publishing Company.

AUTHOR KEYWORDS: Black hole; quantum gravity; thermal fluctuation
PUBLISHER: World Scientific Publishing Co. Pte Ltd


Nakhaee, M., Ketabi, S.A., Peeters, F.M. Tight-binding model for borophene and borophane (2018) 97 (12), art. no. 125424, .

DOI: 10.1103/PhysRevB.97.125424

Starting from the simplified linear combination of atomic orbitals method in combination with first-principles calculations, we construct a tight-binding (TB) model in the two-centre approximation for borophene and hydrogenated borophene (borophane). The Slater and Koster approach is applied to calculate the TB Hamiltonian of these systems. We obtain expressions for the Hamiltonian and overlap matrix elements between different orbitals for the different atoms and present the SK coefficients in a nonorthogonal basis set. An anisotropic Dirac cone is found in the band structure of borophane. We derive a Dirac low-energy Hamiltonian and compare the Fermi velocities with that of graphene. © 2018 American Physical Society.

PUBLISHER: American Physical Society


Mirzakhani, M., Zarenia, M., Vasilopoulos, P., Ketabi, S.A., Peeters, F.M. Landau levels in biased graphene structures with monolayer-bilayer interfaces (2017) 96 (12), art. no. 125430, .

DOI: 10.1103/PhysRevB.96.125430

The electron energy spectrum in monolayer-bilayer-monolayer and in bilayer-monolayer-bilayer graphene structures is investigated and the effects of a perpendicular magnetic field and electric bias are studied. Different types of monolayer-bilayer interfaces are considered as zigzag (ZZ) or armchair (AC) junctions which modify considerably the bulk Landau levels (LLs) when the spectra are plotted as a function of the center coordinate of the cyclotron orbit. Far away from the two interfaces, one obtains the well-known LLs for extended monolayer or bilayer graphene. The LL structure changes significantly at the two interfaces or junctions where the valley degeneracy is lifted for both types of junctions, especially when the distance between them is approximately equal to the magnetic length. Varying the nonuniform bias and the width of this junction-to-junction region in either structure strongly influence the resulting spectra. Significant differences exist between ZZ and AC junctions in both structures. The densities of states (DOSs) for unbiased structures are symmetric in energy whereas those for biased structures are asymmetric. An external bias creates interface LLs in the gaps between the LLs of the unbiased system in which the DOS can be quite small. Such a pattern of LLs can be probed by scanning tunneling microscopy. © 2017 American Physical Society.

PUBLISHER: American Physical Society


Derakhshan, V., Ketabi, S.A. Sizable band gap in organometallic topological insulator (2017) 85, pp. 253-258.

DOI: 10.1016/j.physe.2016.09.003

Based on first principle calculation when Ceperley–Alder and Perdew–Burke–Ernzerh type exchange-correlation energy functional were ado