Exchange-mediated magnetic blue-shift of the band-gap energy in the antiferromagnetic semiconductor MnTe
In magnetic semiconductors the optical spectrum and, in particular, the absorption edge representing the band-gap are strongly affected by the onset of the magnetic order. This contribution to the band-gap energy has hitherto been described theoretically in terms of a Heisenberg Hamiltonian, in whic...
| Main Authors: | , , , , , , |
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| Format: | Article |
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IOP Publishing
2020-01-01
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| Series: | New Journal of Physics |
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| Online Access: | https://doi.org/10.1088/1367-2630/aba0e7 |
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| author | D Bossini M Terschanski F Mertens G Springholz A Bonanni G S Uhrig M Cinchetti |
| author_facet | D Bossini M Terschanski F Mertens G Springholz A Bonanni G S Uhrig M Cinchetti |
| author_sort | D Bossini |
| collection | DOAJ |
| description | In magnetic semiconductors the optical spectrum and, in particular, the absorption edge representing the band-gap are strongly affected by the onset of the magnetic order. This contribution to the band-gap energy has hitherto been described theoretically in terms of a Heisenberg Hamiltonian, in which a delocalized conduction carrier is coupled to the localized magnetic moments by the exchange interaction. Such models, however, do not take into account the strong correlations displayed in a wide variety of magnetic semiconductors, which are responsible for the formation of the local moments. In particular, the itinerant carrier itself contributes to the spin moment. Here, we overcome this simplification in a combined experimental and theoretical study of the antiferromagnetic semiconductor α -MnTe. First, we present a spectroscopic optical investigation as a function of temperature, from which we extract the magnetic contribution to the blue-shift of the band-gap. Second, we formulate a minimal model based on a Hubbard–Kondo Hamiltonian. In this model, the itinerant charge is one of the electrons forming the localized magnetic moment, which properly captures correlation effects in the material. Our theory reproduces the experimental findings with excellent quantitative agreement, demonstrating that the magnetic contribution to the band-gap energy of α -MnTe is mediated solely by the exchange interaction. These results describe an intrinsic property of the material, independent of the thickness, substrate and capping layer of the specimen. One of the key findings of the model is that the basic effect, namely a blue-shift of the band-gap due to the establishment of the magnetic order, is a general phenomenon in charge-transfer insulators. The identification of the relevant magnetic interaction discloses the possibility to exploit the effect here discussed to induce a novel regime of coherent spin dynamics, in which spin oscillations on a characteristic time-scale of 100 fs are triggered and are intrinsically coupled to charges. |
| first_indexed | 2024-03-12T16:32:16Z |
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| language | English |
| last_indexed | 2024-03-12T16:32:16Z |
| publishDate | 2020-01-01 |
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| series | New Journal of Physics |
| spelling | doaj.art-399f4e148910493e8ec19de10fad78b62023-08-08T15:25:51ZengIOP PublishingNew Journal of Physics1367-26302020-01-0122808302910.1088/1367-2630/aba0e7Exchange-mediated magnetic blue-shift of the band-gap energy in the antiferromagnetic semiconductor MnTeD Bossini0https://orcid.org/0000-0003-3537-497XM Terschanski1F Mertens2G Springholz3A Bonanni4G S Uhrig5M Cinchetti6Lehrstuhl für Experimentalphysik VI, Technische Universität Dortmund , Otto-Hahn Straße 4, 44227 Dortmund, GermanyLehrstuhl für Experimentalphysik VI, Technische Universität Dortmund , Otto-Hahn Straße 4, 44227 Dortmund, GermanyLehrstuhl für Experimentalphysik VI, Technische Universität Dortmund , Otto-Hahn Straße 4, 44227 Dortmund, GermanyInstitute of Semiconductor and Solid State Physics, Johannes Kepler University Linz , Altenbergerstr. 69, 4040 Linz, AustriaInstitute of Semiconductor and Solid State Physics, Johannes Kepler University Linz , Altenbergerstr. 69, 4040 Linz, AustriaLehrstuhl für Theoretische Physik I, Technische Universität Dortmund , Otto-Hahn Straße 4, 44221 Dortmund, GermanyLehrstuhl für Experimentalphysik VI, Technische Universität Dortmund , Otto-Hahn Straße 4, 44227 Dortmund, GermanyIn magnetic semiconductors the optical spectrum and, in particular, the absorption edge representing the band-gap are strongly affected by the onset of the magnetic order. This contribution to the band-gap energy has hitherto been described theoretically in terms of a Heisenberg Hamiltonian, in which a delocalized conduction carrier is coupled to the localized magnetic moments by the exchange interaction. Such models, however, do not take into account the strong correlations displayed in a wide variety of magnetic semiconductors, which are responsible for the formation of the local moments. In particular, the itinerant carrier itself contributes to the spin moment. Here, we overcome this simplification in a combined experimental and theoretical study of the antiferromagnetic semiconductor α -MnTe. First, we present a spectroscopic optical investigation as a function of temperature, from which we extract the magnetic contribution to the blue-shift of the band-gap. Second, we formulate a minimal model based on a Hubbard–Kondo Hamiltonian. In this model, the itinerant charge is one of the electrons forming the localized magnetic moment, which properly captures correlation effects in the material. Our theory reproduces the experimental findings with excellent quantitative agreement, demonstrating that the magnetic contribution to the band-gap energy of α -MnTe is mediated solely by the exchange interaction. These results describe an intrinsic property of the material, independent of the thickness, substrate and capping layer of the specimen. One of the key findings of the model is that the basic effect, namely a blue-shift of the band-gap due to the establishment of the magnetic order, is a general phenomenon in charge-transfer insulators. The identification of the relevant magnetic interaction discloses the possibility to exploit the effect here discussed to induce a novel regime of coherent spin dynamics, in which spin oscillations on a characteristic time-scale of 100 fs are triggered and are intrinsically coupled to charges.https://doi.org/10.1088/1367-2630/aba0e7optical spectroscopymagnetismsolid state physicscorrelated materialssemiconductors |
| spellingShingle | D Bossini M Terschanski F Mertens G Springholz A Bonanni G S Uhrig M Cinchetti Exchange-mediated magnetic blue-shift of the band-gap energy in the antiferromagnetic semiconductor MnTe New Journal of Physics optical spectroscopy magnetism solid state physics correlated materials semiconductors |
| title | Exchange-mediated magnetic blue-shift of the band-gap energy in the antiferromagnetic semiconductor MnTe |
| title_full | Exchange-mediated magnetic blue-shift of the band-gap energy in the antiferromagnetic semiconductor MnTe |
| title_fullStr | Exchange-mediated magnetic blue-shift of the band-gap energy in the antiferromagnetic semiconductor MnTe |
| title_full_unstemmed | Exchange-mediated magnetic blue-shift of the band-gap energy in the antiferromagnetic semiconductor MnTe |
| title_short | Exchange-mediated magnetic blue-shift of the band-gap energy in the antiferromagnetic semiconductor MnTe |
| title_sort | exchange mediated magnetic blue shift of the band gap energy in the antiferromagnetic semiconductor mnte |
| topic | optical spectroscopy magnetism solid state physics correlated materials semiconductors |
| url | https://doi.org/10.1088/1367-2630/aba0e7 |
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