Magnetic Field Splitting and Dispersion of the Lower 1S‐Exciton Polariton in KI and RbI

Fröhlich, D.; Kirchhoff,; Köhler, P.; Nieswand, W.

doi:10.1002/pssb.2221580126

Cited by 24 publications

(7 citation statements)

References 23 publications

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“…The splitting shows a pronounced dependence on wave vector k. There is even a change of sign of the splitting. This feature is not observed in similar experiments in alkali halides [8]. We can show that this surprising k-dependence of the splitting is caused by peculiarities of the band structure of CuCI.…”

Section: Introductionmentioning

confidence: 47%

“…As discussed in detail in [8] we have to distinguish the energy splitting of the measured resonance peaks and the polariton splitting. The resonances belong to slightly dgferent k-values whereas the polariton splitting AE is defined as the energy difference between the two branches ( M = -t 1) at the same k-value.…”

Section: Data Evaluation and Discussionmentioning

confidence: 99%

“…Details of the experimental method and the optical setup are given in a recent publication [8]. The measurements were done on ultrapure single crystals of CuCl with different orientations (magnetic field and optical beams along [001], [110], or [lll]).…”

Section: Methodsmentioning

confidence: 99%

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Dispersion of the Exciton Polariton Branches in CuCl and Their k‐Dependent Splitting in a Magnetic Field

Fröhlich

Köhler

Nieswand

et al. 1991

Physica Status Solidi (b)

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The method of three-photon difference-frequency generation is used to measure resonances on the lower polariton branch in CuC1. Due to the small linewidth of the resonances (smallest width 80 FeVj it is possible to determine the splitting of the lower branch in a magnetic field at different k-values for the first time. Resonances on the upper polariton branches and on the longitudinal exciton branches can also be excited with the use of two-and three-photon sum-frequency generation and two-photon absorption. The rather peculiar wavevector-dependent splitting of the lower polariton branch is explained quantitatively by taking into account the field induced mixing of the Z,-and Zl, ,-excitons.Mit Hilfe der Dreiphotonen-Differenzfrequenzerzeugung konnen Resonanzen auf dem unteren Polaritonast in CuCl angeregt werden. Aufgrund der geringen Linienbreite der Resonanzen (kleinste Breite 80 peV) kann erstmals die k-abhingige Magnetfeldaufspaltung des unteren Astes gemessen werden. Mittels der Zwei-und Dreiphotonen-Summenfrequenzerzeugung und der Zweiphotonenabsorption konnen aul3erdem sowohl Resonanzen auf den oberen Polaritonasten als auch die longitudinalen Exzitonen angeregt werden. Die wellenzahlabhangige Aufspaltung des unteren Polaritonastes wird quantitativ durch die Beriicksichtigung der feldinduzierten Mischung der Z,-und Z,, ,-Exzitonen erkliirt.

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Section: Introductionmentioning

confidence: 47%

Section: Data Evaluation and Discussionmentioning

confidence: 99%

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Dispersion of the Exciton Polariton Branches in CuCl and Their k‐Dependent Splitting in a Magnetic Field

Fröhlich

Köhler

Nieswand

et al. 1991

Physica Status Solidi (b)

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“…This feature is neither reproduced by theory nor assigned to vibronic replicas (51), as the latter would be strongly polarization dependent. We tentatively assign this feature to a polaritonic stopband (59,60): a strong, characteristic reflection found between the transversal and the longitudinal exciton-polariton branches. Similar features are observed in quasione-dimensional polymer crystals and TCNQ crystals (61)(62)(63)(64).…”

Section: Resultsmentioning

confidence: 86%

Low-lying excited states in crystalline perylene

Rangel

Rinn

Sharifzadeh

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Organic materials are promising candidates for advanced optoelectronics and are used in light-emitting diodes and photovoltaics. However, the underlying mechanisms allowing the formation of excited states responsible for device functionality, such as exciton generation and charge separation, are insufficiently understood. This is partly due to the wide range of existing crystalline polymorphs depending on sample preparation conditions. Here, we determine the linear optical response of thin-film single-crystal perylene samples of distinct polymorphs in transmission and reflection geometries. The sample quality allows for unprecedented high-resolution spectroscopy, which offers an ideal opportunity for judicious comparison between theory and experiment. Excellent agreement with firstprinciples calculations for the absorption based on the GW plus Bethe-Salpeter equation (GW-BSE) approach of many-body perturbation theory (MBPT) is obtained, from which a clear picture of the low-lying excitations in perylene emerges, including evidence of an exciton-polariton stopband, as well as an assessment of the commonly used Tamm-Dancoff approximation to the GW-BSE approach. Our findings on this well-controlled system can guide understanding and development of advanced molecular solids and functionalization for applications. molecular crystals | many-body perturbation theory | excited states | spectroscopy

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“…The measurements were done on cleaved samples at 1.5 K. The two-photon signal was monitored via the o or vr luminescence of self-trapped excitons [10]. For further details of the experimental setup we refer to previous publications on twoand threephoton experiments [4,11]. As discussed before the polarization selection rules are the same as for classical twophoton processes, except for the fact that now odd-parity states are excited.…”

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confidence: 99%

Two-photon spectroscopy of odd-parity states

1994

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Magnetic-dipole two-photon absorption (MD-TPA) is introduced as a new spectroscopic technique for the study of odd-parity states. Contrary to the classical electric-dipole two-photon absorption (ED-TPA), where only spin-allowed even-parity transitions can be excited, MD-TPA allows us to excite spin-forbidden odd-parity states. This new technique is therefore very well suited to study paraexcitons in semiconductors and insulators. As examples MD-TPA measurements of RbI, NaI, and NaBr are presented.PACS numbers: 42.65.k, 71.35.+z Two-photon absorption (TPA) was first treated theoretically more than sixty years ago by Goppert-Mayer [1] using second-order perturbation theory. With respect to selection rules two-photon processes can be interpreted as two successive one-photon transitions. From Laporte's rule which states that one-photon dipole transitions are only allowed between states of diferent parity, one immediately derives that two-photon transitions are allowed only between states of the same parity. About thirty years ago Hopfield and Worlock [2] were the first to do two-photon spectroscopy on excitons. In agreement with the above-mentioned selection rule they found that in alkali halides two-photon transitions are indeed allowed to even-parity P excitons but strictly forbidden to oddparity S excitons.In order to excite odd-parity states by nonlinear spectroscopy one has to step onto three-photon spectroscopy (TPS) as was again demonstrated in alkali halides [3]. By the use of di8erent three-photon techniques one can observe the polariton dispersion and the longitudinal exciton with high accuracy [4].In this Letter we introduce a new spectroscopic technique, which allows us to excite odd-parity states by two-photon absorption. Contrary to classical two-photon absorption where both photons induce electric-dipole transitions (ED-TPA), we consider two-photon processes where one of the photons induces a magnetic-dipole transition and the other an electric-dipole transition.In the following we will briefly outline the theoretical background of magnetic-dipole two-photon absorption (MD-TPA).As in the case of ED-TPA [5] one can derive the twophoton transition probability Wg f for MD-TPA from second-order perturbation theory: -&(fl(MD)2]i)(il(ED) ilg) Ws f (x E, -Eghindi (fI (I&)i I ') (& I (s&)2 I g) ) E, -Eg -~g x 6(Ef -Egh(u)i + (d2)), where E~a nd Ef refer to the energy of the ground and final states, respectively. As intermediate states~i ) (energy E, ) one has to consider all states which are allowed for electric-dipole transitions from the ground state~g ).(ED)"and (MD) refer to the electricand magneticdipole operator, respectively. v = 1, 2 labels the incoming photons with energies hu and polarization directions e . In Eq.(1) we have assumed that the first transition (g~i) is of electric-dipole type, which is expected to be the case for many solids, where the lowest energy transitions (e.g. , 1S excitons) are dipole allowed.As first shown by Inoue and Toyozawa [5), the twophoton polarization selection rules c...

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Magnetic Field Splitting and Dispersion of the Lower 1S‐Exciton Polariton in KI and RbI

Cited by 24 publications

References 23 publications

Dispersion of the Exciton Polariton Branches in CuCl and Their k‐Dependent Splitting in a Magnetic Field

Dispersion of the Exciton Polariton Branches in CuCl and Their k‐Dependent Splitting in a Magnetic Field

Low-lying excited states in crystalline perylene

Two-photon spectroscopy of odd-parity states

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