lnu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Theoretical studies of single magnetic impurities on the surface of semiconductors and topological insulators
Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.ORCID iD: 0000-0002-7831-7214
Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.ORCID iD: 0000-0003-4489-7561
Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
Show others and affiliations
2013 (English)In: MRS Online Proceedings Library/Volume 1564/2013, Materials Research Society, 2013Conference paper, Published paper (Refereed)
Abstract [en]

We present results of theoretical studies of transition metal dopants in GaAs, based on microscopic tight-binding model and ab-initio calculations. We focus in particular on how the vicinity of surface affects the properties of the hole-acceptor state, its magnetic anisotropy and its magnetic coupling to the magnetic dopant.  In agreement with STM experiments, Mn substitutional dopants on the (110) GaAs surface give rise to a deep acceptor state, whose wavefunction is localized around the Mn center. We discuss a refinement of the theory that introduces explicitly the d-levels for the TM dopant. The explicit inclusion of d-levels is particularly important for addressing recent STM experiments on substitutional Fe in GaAs. In the second part of the paper we discuss an analogous investigation of single dopants in Bi2Se3 three-dimensional topological insulators, focusing in particular on how substitutional impurities positioned on the surface affect the electronic structure in the gap.  We present explicit results for BiSe antisite defects and compare with STM experiments.

Place, publisher, year, edition, pages
Materials Research Society, 2013.
National Category
Condensed Matter Physics
Research subject
Physics, Condensed Matter Physics
Identifiers
URN: urn:nbn:se:lnu:diva-28030DOI: 10.1557/opl.2013.1088Scopus ID: 2-s2.0-84899071073OAI: oai:DiVA.org:lnu-28030DiVA: diva2:639874
Conference
2013 MRS Spring Meeting & Exhibit
Available from: 2013-08-10 Created: 2013-08-10 Last updated: 2017-05-08Bibliographically approved
In thesis
1. Magnetic solotronics near the surface of a semiconductor and a topological insulator
Open this publication in new window or tab >>Magnetic solotronics near the surface of a semiconductor and a topological insulator
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Technology where a solitary dopant acts as the active component of an opto-electronic device is an emerging  field known as solotronics, and bears the promise to revolutionize the way in which information is stored, processed and transmitted. Magnetic doped semiconductors and in particular (Ga, Mn)As, the archetype of dilute magnetic semiconductors, and topological insulators (TIs), a new phase of quantum matter with unconventional characteristics, are two classes of quantum materials that have the potential to advance spin-electronics technology. The quest to understand and control, at the atomic level, how a few magnetic atoms precisely positioned in a complex environment respond to external stimuli, is the red thread that connects these two quantum materials in the research presented here.

The goal of the thesis is in part to elucidate the properties of transition metal (TM) impurities near the surface of GaAs semiconductors with focus on their response to local magnetic and electric fields, as well as to investigate the real-time dynamics of their localized spins. Our theoretical analysis, based on density functional theory (DFT) and using tight-binding (TB) models, addresses the mid-gap electronic structure, the local density of states (LDOS) and the magnetic anisotropy energy of individual Mn and Fe impurities near the (110) surface of GaAs. We investigate the effect of a magnetic field on the Mn acceptor LDOS measured in cross-sectional scanning tunneling microscopy, and provide an explanation of why the experimental LDOS images depend weakly on the field direction despite the strongly anisotropic nature of the Mn acceptor wavefunction. We also investigate the effects of a local electrostatic field generated by nearby charged As vacancies, on individual and pairs of ferromagnetically coupled magnetic dopants near the surface of GaAs, providing a means to control electrically the exchange interaction of Mn pairs. Finally, using the mixed quantum-classical scheme for spin dynamics, we calculate explicitly the time evolution of the Mn spin and its bound acceptor, and analyze the dynamic interaction between pairs of ferromagnetically coupled magnetic impurities in a nanoscaled semiconductor.

The second part of the thesis deals with the theoretical investigation of a single substitutional Mn impurity and its associated acceptor state on the (111) surface of Bi2Se3 TI, using an approach that combines DFT and TB calculations. Our analysis clarifies the crucial role played by the spatial overlap and the quasi-resonant coupling between the Mn-acceptor and the topological surface states inside the Bi2Se3 band gap, in the opening of a gap at the Dirac point. Strong electronic correlations are also found to contribute significantly to the mechanism leading to the gap, since they control the hybridization between the p orbitals of nearest-neighbor Se atoms and the acceptor spin-polarization. Our results explain the effects of inversion-symmetry and time-reversal symmetry breaking on the electronic states in the vicinity of the Dirac point, and contribute to clarifying the origin of surface-ferromagnetism in TIs. The promising potential of magnetic-doped TIs accentuates the importance of our contribution to the understanding of the interplay between magnetic order and topological protected surface states.

Place, publisher, year, edition, pages
Linnaeus University Press, 2015. 251 p.
Series
Linnaeus University Dissertations, 211/2015
Keyword
Magnetic solotronics, Transition metal dopants, Dilute magnetism in semiconductors and topological insulators, Atomistic tight-binding models, DFT, Spin dynamics, Magnetic anisotropy, Scanning tunneling microscope.
National Category
Condensed Matter Physics
Research subject
Physics, Condensed Matter Physics
Identifiers
urn:nbn:se:lnu:diva-40398 (URN)978-91-87925-49-8 (ISBN)
Public defence
2015-03-27, Ny227, Kalmar Nyckel, Kalmar, 13:00 (English)
Opponent
Supervisors
Available from: 2015-02-25 Created: 2015-02-25 Last updated: 2016-11-01Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopusFulltext

Authority records BETA

Mahani, Mohammad RezaPertsova, AnnaCanali, Carlo M.Islam, Fhokrul

Search in DiVA

By author/editor
Mahani, Mohammad RezaPertsova, AnnaCanali, Carlo M.Islam, Fhokrul
By organisation
Department of Physics and Electrical Engineering
Condensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 129 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf