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The lowest energy states in transition metal dichalcogenide (TMD) monolayers follow valley selection rules, which have attracted vast interest due to the possibility of encoding and processing of quantum information. However, these quantum…

Mesoscale and Nanoscale Physics · Physics 2024-03-22 Sergii Morozov , Torgom Yezekyan , Christian Wolff , Sergey I. Bozhevolnyi , N. Asger Mortensen

Monolayer transition metal dichalcogenides have emerged as prominent candidates to explore the complex interplay between the spin and the valleys degrees of freedom. The strong spin-orbit interaction and broken inversion symmetry within…

Layered transition-metal dichalcogenides have attracted great interest in the last few years. Thinned down to the monolayer limit they change from an indirect band structure to a direct band gap in the visible region. Due to the monolayer…

Mesoscale and Nanoscale Physics · Physics 2017-02-01 Jan Kuhnert , Arash Rahimi-Iman , Wolfram Heimbrodt

Monolayer group-VIB transition metal dichalcogenides have recently emerged as a new class of semiconductors in the two-dimensional limit. The attractive properties include: the visible range direct band gap ideal for exploring…

Mesoscale and Nanoscale Physics · Physics 2015-07-30 Hongyi Yu , Xiaodong Cui , Xiaodong Xu , Wang Yao

Excitons in monolayer transition-metal dichalcogenides (TMDs) have garnered significant attention because of their large binding energies due to weakly screened Coulomb interaction, and direct bandgap at the K/K$^\prime$ point in the…

Monolayer transition metal dichalcogenides (TMDs) hold great promise for future information processing applications utilizing a combination of electron spin and valley pseudospin. This unique spin system has led to observation of the valley…

Mesoscale and Nanoscale Physics · Physics 2019-05-30 T. P. Lyons , S. Dufferwiel , M. Brooks , F. Withers , T. Taniguchi , K. Watanabe , K. S. Novoselov , G. Burkard , A. I. Tartakovskii

The optical properties of transition metal dichalcogenide monolayers are widely dominated by excitons, Coulomb-bound electron-hole pairs. These quasi-particles exhibit giant oscillator strength and give rise to narrow-band, well-pronounced…

Mesoscale and Nanoscale Physics · Physics 2018-07-13 Christian Schneider , Mikhail M. Glazov , Tobias Korn , Sven Höfling , Bernhard Urbaszek

Zeeman effect induced by the magnetic field introduces a splitting between the two valleys at K$^+$ and K$^-$ points of the Brillouin zone in monolayer semiconducting transition metal dichalcogenides. In consequence, the photoluminescence…

Mesoscale and Nanoscale Physics · Physics 2020-12-30 Tomasz Smoleński , Tomasz Kazimierczuk , Mateusz Goryca , Karol Nogajewski , Marek Potemski , Piotr Kossacki

Excitons, Coulomb bound electron-hole pairs, are composite bosons and their interactions in traditional semiconductors lead to condensation and light amplification. The much stronger Coulomb interaction in transition metal dichalcogenides…

Mesoscale and Nanoscale Physics · Physics 2017-04-05 M. Manca , M. M. Glazov , C. Robert , F. Cadiz , T. Taniguchi , K. Watanabe , E. Courtade , T. Amand , P. Renucci , X. Marie , G. Wang , B. Urbaszek

Monolayers of transition metal dichalcogenides are promising materials for valleytronic applications, since they possess two individually addressable excitonic transitions at the non-equivalent $K$ and $K'$ points with different spins,…

Mesoscale and Nanoscale Physics · Physics 2020-07-01 Malte Selig , Florian Katsch , Samuel Brem , Garnik F. Mkrtchian , Ermin Malic , Andreas Knorr

We describe recent experimental efforts to perform polarization-resolved optical spectroscopy of monolayer transition-metal dichalcogenide semiconductors in very large pulsed magnetic fields to 65 tesla. The experimental setup and technical…

Mesoscale and Nanoscale Physics · Physics 2016-12-06 Andreas V. Stier , Kathleen M. McCreary , Berend T. Jonker , Junichiro Kono , Scott A. Crooker

The optical properties of transition metal dichalcogenide monolayers such as the two-dimensional semiconductors MoS$_2$ and WSe$_2$ are dominated by excitons, Coulomb bound electron-hole pairs. The light emission yield depends on whether…

Materials Science · Physics 2016-03-23 J. P. Echeverry , B. Urbaszek , T. Amand , X. Marie , I. C. Gerber

In transition metal dichalcogenides, the valley degree of freedom directly couples valley-polarised excitons - excited by circularly polarised light - to valley-dependent chiral photons, enabling ultrafast light-driven valleytronics.…

Optical interband transitions in monolayer transition metal dichalcogenides such as WSe2 and MoS2 are governed by chiral selection rules. This allows efficient optical initialization of an electron in a specific K-valley in momentum space.…

Mesoscale and Nanoscale Physics · Physics 2014-09-09 G. Wang , L. Bouet , D. Lagarde , M. Vidal , A. Balocchi , T. Amand , X. Marie , B. Urbaszek

Monolayer transition metal dichalcogenides (TMDCs) are direct gap semiconductors with unique potential for ultrathin light emitters. Yet, their photoluminescence (PL) is not completely understood. We compute the radiative recombination rate…

Materials Science · Physics 2018-07-20 Hsiao-Yi Chen , Maurizia Palummo , Davide Sangalli , Marco Bernardi

The two dimensional layered transition metal dichalcogenides provide new opportunities in future valley based information processing and also provide ideal platform to study excitonic effects. At the center of various device physics toward…

Materials Science · Physics 2017-04-05 Dong Sun , Jiawei Lai , Junchao Ma , Qinsheng Wang , Jing Liu

Modern electronic devices heavily rely on the accurate control of charge and spin of electrons. The emergence of controllable valley degree of freedom brings new possibilities and presents a promising prospect towards valleytronics.…

We show that inversion symmetry breaking together with spin-orbit coupling leads to coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides, making possible controls of spin and valley in these 2D materials.…

Mesoscale and Nanoscale Physics · Physics 2012-05-09 Di Xiao , Gui-Bin Liu , Wanxiang Feng , Xiaodong Xu , Wang Yao

Preserving a high degree of valley polarization of excitons in photo-excited transition-metal dichalcogenide monolayers (TMD-MLs) is desirable for the valley-based photonic applications, but widely recognized as a hard task hindered by the…

Mesoscale and Nanoscale Physics · Physics 2020-10-13 Ping-Yuan Lo , Guan-Hao Peng , Wei-Hua Li , Yi Yang , Shun-Jen Cheng

Inelastic electron tunneling in a scanning tunneling microscope (STM) is used to generate excitons in monolayer tungsten disulfide (WS$_2$). Excitonic electroluminescence is measured both at positive and negative sample bias. Using optical…