TY - JOUR

T1 - Signature of lattice dynamics in twisted 2D homo-hetero bilayers

AU - Pan, Yang

AU - Li, S.

AU - Rahaman, Mahfujur

AU - Milekhin, Ilya

AU - Zahn, Dietrich R.T.

N1 - Acknowledgments: The authors gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft (DFG) for Projects ZA 146/43-1, ZA 146/44-1, and ZA 146/47-1.

PY - 2022/10/1

Y1 - 2022/10/1

N2 - Twisted 2D bilayer materials are created by artificial stacking of two monolayer crystal networks of 2D materials with a desired twisting angle θ. The material forms a moiré superlattice due to the periodicity of both top and bottom layer crystal structure. The optical properties are modified by lattice reconstruction and phonon renormalization, which makes optical spectroscopy an ideal characterization tool to study novel physics phenomena. Here, we report a Raman investigation on a full period of the twisted bilayer (tB) WSe2 moiré superlattice (i.e. 0$^{\circ}\,\leqslant\,\theta\,\leqslant\,$ 60∘). We observe that the intensity ratio of two Raman peaks, $B_{2g}$ and $E_{2g}/A_{1g}$ correlates with the evolution of the moiré period. The Raman intensity ratio as a function of twisting angle follows an exponential profile matching the moiré period with two local maxima at 0∘ and 60∘ and a minimum at 30∘. Using a series of temperature-dependent Raman and photoluminescence measurements as well as ab initio calculations, the intensity ratio $I_{B_{2g}}/I_{{E_{2g}}/{A_{1g}}}$ is explained as a signature of lattice dynamics in tB WSe2 moiré superlattices. By further exploring different material combinations of twisted hetero-bilayers, the results are extended for all kinds of Mo- and W-based transition metal dichalcogenides.

AB - Twisted 2D bilayer materials are created by artificial stacking of two monolayer crystal networks of 2D materials with a desired twisting angle θ. The material forms a moiré superlattice due to the periodicity of both top and bottom layer crystal structure. The optical properties are modified by lattice reconstruction and phonon renormalization, which makes optical spectroscopy an ideal characterization tool to study novel physics phenomena. Here, we report a Raman investigation on a full period of the twisted bilayer (tB) WSe2 moiré superlattice (i.e. 0$^{\circ}\,\leqslant\,\theta\,\leqslant\,$ 60∘). We observe that the intensity ratio of two Raman peaks, $B_{2g}$ and $E_{2g}/A_{1g}$ correlates with the evolution of the moiré period. The Raman intensity ratio as a function of twisting angle follows an exponential profile matching the moiré period with two local maxima at 0∘ and 60∘ and a minimum at 30∘. Using a series of temperature-dependent Raman and photoluminescence measurements as well as ab initio calculations, the intensity ratio $I_{B_{2g}}/I_{{E_{2g}}/{A_{1g}}}$ is explained as a signature of lattice dynamics in tB WSe2 moiré superlattices. By further exploring different material combinations of twisted hetero-bilayers, the results are extended for all kinds of Mo- and W-based transition metal dichalcogenides.

KW - 2D material

KW - Raman spectroscopy

KW - TMDC

KW - moiré

KW - phonon

KW - twisted bilayer

UR - https://www.mendeley.com/catalogue/503d6443-8589-3e75-a58e-e04bed2ac826/

U2 - 10.1088/2053-1583/ac83d4

DO - 10.1088/2053-1583/ac83d4

M3 - Article

VL - 9

JO - 2D Materials

JF - 2D Materials

SN - 2053-1583

IS - 4

M1 - 045018

ER -