TY - JOUR
T1 - Valley-contrasting optics of interlayer excitons in Mo- and W-based bulk transition metal dichalcogenides
AU - Arora, Ashish
AU - Deilmann, Thorsten
AU - Marauhn, Philipp
AU - Drueppel, Matthias
AU - Schneider, Robert
AU - Molas, Maciej R.
AU - Vaclavkova, Diana
AU - de Vasconcellos, Steffen Michaelis
AU - Rohlfing, Michael
AU - Potemski, Marek
AU - Bratschitsch, Rudolf
PY - 2018
Y1 - 2018
N2 - Recently, spatially indirect (interlayer) excitons have been discovered in bulk 2H-MoTe2. They are theoretically predicted to exist in other Mo-based transition metal dichalcogenides (TMDCs) and are expected to be present in W-based TMDCs as well. We investigate interlayer excitons (X-IL) in bulk 2H-MoSe2 and 2H-WSe2 using valley-resolved magneto-reflectance spectroscopy under high magnetic fields of up to 29 T combined with ab initio GW-BSE calculations. In the experiments, we observe interlayer excitons in MoSe2, while their signature is surprisingly absent in WSe2. In the calculations, we find that interlayer excitons exist in both Mo- and W-based TMDCs. However, their energetic positions and their oscillator strengths are remarkably different. In Mo-based compounds, the interlayer exciton resonance X-IL is clearly separated from the intralayer exciton X1sA and has a high amplitude. In contrast, in W-based compounds, X-IL is close in energy to the intralayer A exciton X1sA and possesses a small oscillator strength, which explains its absence in the experimental data of WSe2. Our combined experimental and theoretical observations demonstrate that interlayer excitons can gain substantial oscillator strength by mixing with intralayer states and hence pave the way for exploring interlayer exciton physics in Mo-based bulk transition metal dichalcogenides.
AB - Recently, spatially indirect (interlayer) excitons have been discovered in bulk 2H-MoTe2. They are theoretically predicted to exist in other Mo-based transition metal dichalcogenides (TMDCs) and are expected to be present in W-based TMDCs as well. We investigate interlayer excitons (X-IL) in bulk 2H-MoSe2 and 2H-WSe2 using valley-resolved magneto-reflectance spectroscopy under high magnetic fields of up to 29 T combined with ab initio GW-BSE calculations. In the experiments, we observe interlayer excitons in MoSe2, while their signature is surprisingly absent in WSe2. In the calculations, we find that interlayer excitons exist in both Mo- and W-based TMDCs. However, their energetic positions and their oscillator strengths are remarkably different. In Mo-based compounds, the interlayer exciton resonance X-IL is clearly separated from the intralayer exciton X1sA and has a high amplitude. In contrast, in W-based compounds, X-IL is close in energy to the intralayer A exciton X1sA and possesses a small oscillator strength, which explains its absence in the experimental data of WSe2. Our combined experimental and theoretical observations demonstrate that interlayer excitons can gain substantial oscillator strength by mixing with intralayer states and hence pave the way for exploring interlayer exciton physics in Mo-based bulk transition metal dichalcogenides.
U2 - 10.1039/c8nr03764g
DO - 10.1039/c8nr03764g
M3 - Journal article
C2 - 30090905
SN - 2040-3364
VL - 10
SP - 15571
EP - 15577
JO - Nanoscale
JF - Nanoscale
IS - 33
ER -