Optically bright p-excitons indicating strong Coulomb coupling in transition-metal dichalcogenides. (3rd August 2015)

• Record Type: Journal Article
• Authors: Stroucken, T; Koch, S W
• Is Part Of: Journal of physics. Volume 27:Number 34(2015)
• Publication Date: 2015-08-03
• Subjects: transition metal dichalcogenides -- excitons -- excitonic insulator -- optical selection rules; Condensed matter -- Periodicals; Matière condensée -- Périodiques; Vaste stoffen; Vloeistoffen; Natuurkunde; Electronic journals; Computer network resources; 530.4105
• DOI: 10.1088/0953-8984/27/34/345003
• Languages: English
• ISSNs: 0953-8984

Abstract

Abstract: It is shown that the strong Coulomb coupling in intrinsic suspended semiconducting transition metal dichalcogenides can exceed the critical value needed for an excitonic ground state. The dipole-allowed optical excitations then correspond to intra-excitonic transitions such that the optically bright excitonic transitions near the Dirac points have a p -like symmetry, whereas the s -like states are dipole forbidden. The large intrinsic coupling strength seems to be a generic property of the semiconducting transition metal dichalcogenides and strong Coulomb-coupling signatures in the form of the optical selection rules can be observed even in samples grown on typical substrates like SiO2 . For the examples of WS2 and WSe2, excellent agreement of the computed excitonic resonance energies with recent experiments is demonstrated.