Robust optical emission polarization in MoS<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>monolayers through selective valley excitation

Sallen, Gregory; Bouet, L.; Marie, X.; Wang, G; Zhu, Chao; Han, Wenjuan; Lü, Yan; Tan, Ping‐Heng; Amand, T.; Liu, Baoli; Urbaszek, B.

doi:10.1103/physrevb.86.081301

Cited by 424 publications

(335 citation statements)

References 25 publications

Supporting

Mentioning

315

Contrasting

Unclassified

Order By: Relevance

“…Our experimental observations also rule out a spin-Zeeman contribution to the measured splitting. In fact, the strong spin-orbit interaction in both the conduction and valence band of WSe 2 (refs 24,25) ensures that the spin degree of freedom is frozen out and does not contribute to the B-induced splitting, which is consistent with earlier studies that reported insensitivity of circular dichroism to an in-plane magnetic field 4,26 .…”

supporting

confidence: 80%

Valley Zeeman effect in elementary optical excitations of monolayer WSe2

et al. 2015

View full text Add to dashboard Cite

A monolayer of a transition metal dichalcogenide such as WSe 2 is a two-dimensional direct-bandgap valley-semiconductor 1,2 having an e ective honeycomb lattice structure with broken inversion symmetry. The inequivalent valleys in the Brillouin zone could be selectively addressed using circularly polarized light fields 3-5 , suggesting the possibility for magneto-optical measurement and manipulation of the valley pseudospin degree of freedom 6-8 . Here we report such experiments that demonstrate the valley Zeeman e ect-strongly anisotropic lifting of the degeneracy of the valley pseudospin degree of freedom using an external magnetic field. The valley-splitting measured using the exciton transition deviates appreciably from values calculated using a three-band tight-binding model 9 for an independent electron-hole pair at ±K valleys. We show, on the other hand, that a theoretical model taking into account the strongly bound nature of the exciton yields an excellent agreement with the experimentally observed splitting. In contrast to the exciton, the trion transition exhibits an unexpectedly large valley Zeeman e ect that cannot be understood within the same framework, hinting at a di erent contribution to the trion magnetic moment. Our results raise the possibility of controlling the valley degree of freedom using magnetic fields in monolayer transition metal dichalcogenides or observing topological states of photons strongly coupled to elementary optical excitations in a microcavity 10 .Charge carriers in two-dimensional (2D) layered materials with a honeycomb lattice, such as graphene and transition metal dichalcogenides (TMDs), have a twofold valley degree of freedom labelled by ±K-points of the Brillouin zone, which are related to each other by time-reversal symmetry 7 . In TMDs, the low-energy physics takes place in the vicinity of ±K-points of the conduction and valence bands with Bloch states that are formed primarily from d z 2 and d x 2 −y 2 , d xy orbitals of the transition metal, respectively 9 . The magnetic moment of charged particles in a monolayer TMD arises from two distinct contributions: the intracellular component stems from the hybridization of the d x 2 −y 2 and d xy orbitals as d x 2 −y 2 ± id xy , which provide the Bloch electrons at ±K in the valence band an azimuthal angular momentum along z of l z = ±2h (Fig. 1a). The second-intercellular-contribution originates from the phase winding of the Bloch functions at ±K-points 11-14 . This latter contribution to orbital magnetic moment is different for conduction and valence bands owing to breakdown of electronhole symmetry. Both contributions yield magnetic-field-induced splitting with an opposite sign in the two valleys.In a 2D material such as a monolayer TMD, the current circulation from the orbitals can only be within the plane; as a consequence, the corresponding orbital magnetic moment can only point out-of-plane. A magnetic field (B) along z distinguishes the sense of circulation in 2D, causing opposite energy shifts (− µ· B) in ±K val...

show abstract

supporting

confidence: 80%

Valley Zeeman effect in elementary optical excitations of monolayer WSe2

et al. 2015

View full text Add to dashboard Cite

show abstract

“…96.201113 Introduction. The last few years have witnessed an explosion in research on monolayer transition metal dichalcogenides (TMDCs) driven mainly by their unique optical properties [1][2][3][4][5][6][7][8]. In contrast to their bulk counterparts, the monolayer TMDCs possess a direct band gap [9,10] leading to very strong light-matter interactions.…”

Section: Dark Excitations In Monolayer Transition Metal Dichalcogenidesmentioning

confidence: 99%

Dark excitations in monolayer transition metal dichalcogenides

Deilmann

Thygesen

2017

Phys. Rev. B

View full text Add to dashboard Cite

Monolayers of transition metal dichalcogenides (TMDCs) possess unique optoelectronic properties, including strongly bound excitons and trions. To date, most studies have focused on optically active excitations, but recent experiments have highlighted the existence of dark states, which are equally important in many respects. Here, we use ab initio many-body calculations to unravel the nature of the dark excitations in monolayer MoSe 2 , MoS 2 , WSe 2 , and WS 2 . Our results show that all these monolayer TMDCs host dark states as their lowest neutral and charged excitations. We further show that dark excitons possess larger binding energies than their bright counterparts while the opposite holds for trions.

show abstract

“…Here, we benefit from the chiral optical selection rules in TMDC monolayers, which allow optical excitation in the K þ or K − valley, using σ þ or σ − polarized laser excitation, respectively [26,30,[76][77][78]; see scheme in Fig. 3(a).…”

Section: Valley Polarization and Valley Coherence Manipulationmentioning

confidence: 99%

Excitonic Linewidth Approaching the Homogeneous Limit in MoS2 -Based van der Waals Heterostructures

et al. 2017

Self Cite

View full text Add to dashboard Cite

The strong light-matter interaction and the valley selective optical selection rules make monolayer (ML) MoS 2 an exciting 2D material for fundamental physics and optoelectronics applications. But, so far, optical transition linewidths even at low temperature are typically as large as a few tens of meV and contain homogeneous and inhomogeneous contributions. This prevented in-depth studies, in contrast to the bettercharacterized ML materials MoSe 2 and WSe 2 . In this work, we show that encapsulation of ML MoS 2 in hexagonal boron nitride can efficiently suppress the inhomogeneous contribution to the exciton linewidth, as we measure in photoluminescence and reflectivity a FWHM down to 2 meV at T ¼ 4 K. Narrow optical transition linewidths are also observed in encapsulated WS 2 , WSe 2 , and MoSe 2 MLs. This indicates that surface protection and substrate flatness are key ingredients for obtaining stable, high-quality samples. Among the new possibilities offered by the well-defined optical transitions, we measure the homogeneous broadening induced by the interaction with phonons in temperature-dependent experiments. We uncover new information on spin and valley physics and present the rotation of valley coherence in applied magnetic fields perpendicular to the ML.

show abstract

Robust optical emission polarization in MoS2monolayers through selective valley excitation

Cited by 424 publications

References 25 publications

Valley Zeeman effect in elementary optical excitations of monolayer WSe2

Valley Zeeman effect in elementary optical excitations of monolayer WSe2

Dark excitations in monolayer transition metal dichalcogenides

Excitonic Linewidth Approaching the Homogeneous Limit in MoS2 -Based van der Waals Heterostructures

Contact Info

Product

Resources

About