Identification of spin, valley and moiré quasi-angular momentum of interlayer excitons

Choi, Jin; Regan, Emma C.; Wang, Danqing; Utama, M. Iqbal Bakti; Yang, C. C.; Cain, Jeffrey D.; Qin, Ying; Shen, Yuxia; Zheng, Ziqiong; Watanabe, Kenji; Taniguchi, Takashi; Tongay, Sefaattin; Zettl, Alex; Wang, Feng

doi:10.1038/s41567-019-0631-4

Cited by 106 publications

(114 citation statements)

References 40 publications

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“…These fictitious entities, which consist of particles dressed by their many-body interactions, are usually characteristic of material composition. Yet van der Waals layered materials provide an efficient tuning knob: the twist angle between adjacent layers can turn the semimetal graphene into a Mott insulator 1 , superconductor 2 , or ferromagnet 3 ; topological phases [4][5][6][7] , spin-pseudospin coupling 8 , and shear solitons 9 have been discussed for twisted bilayers of transition metal dichalcogenides (TMDs).…”

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confidence: 99%

Twist-tailoring Coulomb correlations in van der Waals homobilayers

et al. 2020

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The recent discovery of artificial phase transitions induced by stacking monolayer materials at magic twist angles represents a paradigm shift for solid state physics. Twist-induced changes of the single-particle band structure have been studied extensively, yet a precise understanding of the underlying Coulomb correlations has remained challenging. Here we reveal in experiment and theory, how the twist angle alone affects the Coulomb-induced internal structure and mutual interactions of excitons. In homobilayers of WSe 2 , we trace the internal 1s-2p resonance of excitons with phase-locked mid-infrared pulses as a function of the twist angle. Remarkably, the exciton binding energy is renormalized by up to a factor of two, their lifetime exhibits an enhancement by more than an order of magnitude, and the exciton-exciton interaction is widely tunable. Our work opens the possibility of tailoring quasiparticles in search of unexplored phases of matter in a broad range of van der Waals heterostructures.

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confidence: 99%

Twist-tailoring Coulomb correlations in van der Waals homobilayers

et al. 2020

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“…In this Letter, we show that the introduction of a twist angle between the layers can provide a new avenue for engineering the spin-valley properties of TMD bilayers, including homobilayers. Previously, the twist angle has been used to modify the resonance energy of excitons [35,36] and alter their properties due to moiré-induced spatial confinement and hybridization of bands [37][38][39][40][41][42]. Here, we tune the twist angle between the layers to control the momentum alignment of their respective valleys [ Fig.…”

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confidence: 99%

Electrically Tunable Valley Dynamics in Twisted WSe2/WSe2 Bilayers

et al. 2020

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The twist degree of freedom provides a powerful new tool for engineering the electrical and optical properties of van der Waals heterostructures. Here, we show that the twist angle can be used to control the spin-valley properties of transition metal dichalcogenide bilayers by changing the momentum alignment of the valleys in the two layers. Specifically, we observe that the interlayer excitons in twisted WSe 2 =WSe 2 bilayers exhibit a high (>60%) degree of circular polarization (DOCP) and long valley lifetimes (>40 ns) at zero electric and magnetic fields. The valley lifetime can be tuned by more than 3 orders of magnitude via electrostatic doping, enabling switching of the DOCP from ∼80% in the n-doped regime to <5% in the p-doped regime. These results open up new avenues for tunable chiral light-matter interactions, enabling novel device schemes that exploit the valley degree of freedom.

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“…The result is a periodic modulation of the energy landscape in real space with a magnitude in the order of up to 0.15 eV [5,11]. The periodically modulated energy landscape in suitable TMDC hetero-bilayers enables the formation of spatially localized IX states trapped at different superlattice sites [11,14,69] with moiré quasi angular momentum periodically switching the optical selection rules [71] as demonstrated in figure 6b,d-g.…”

Section: Crystal Alignment and Moiré Excitonsmentioning

confidence: 93%

“…and in the design of novel designer quantum nanomaterials. Moreover, vdW structures exhibit potential to access collective excitonic phenomena like high-temperature superfluidity and Bose-Einstein condensation [66][67][68] as well as excitons in moiré-superlattices [11,14,[69][70][71].…”

Section: Introductionmentioning

confidence: 99%

Light–matter interaction in van der Waals hetero-structures

Deilmann

Rohlfing

Wurstbauer

2020

J. Phys.: Condens. Matter

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Even if individual two-dimensional materials own various interesting and unexpected properties, the stacking of such layers leads to van der Waals solids which unite the characteristics of two dimensions with novel features originating from the interlayer interactions. In this topical review, we cover fabrication and characterization of van der Waals heterosructures with a focus on heterobilayers made of monolayers of semiconducting transition metal dichalcogenides. Experimental and theoretical techniques to investigate those heterobilayers are introduced. Most recent findings focusing on different transition metal dichalcogenides heterostructures are presented and possible optical transitions between different valleys, appearance of moiré patterns and signatures of moiré excitons are discussed. The fascinating and fast growing research on van der Waals hetero-bilayers provide promising insights required for their application as emerging quantum-nano materials. arXiv:2002.08066v1 [cond-mat.mes-hall]

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Identification of spin, valley and moiré quasi-angular momentum of interlayer excitons

Cited by 106 publications

References 40 publications

Twist-tailoring Coulomb correlations in van der Waals homobilayers

Twist-tailoring Coulomb correlations in van der Waals homobilayers

Electrically Tunable Valley Dynamics in Twisted WSe2/WSe2 Bilayers

Light–matter interaction in van der Waals hetero-structures

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