Optical Conductivity of MoS2 - School of...
Transcript of Optical Conductivity of MoS2 - School of...
Optical Conductivity of MoS2
Habib Rostami
IPM
10 Mehr 92
• Motivation
• Inversion Symmetry
• Gapped Graphene & Valley contrasting effect
• Monolayer MoS2&optical measurement
• Optical Conductivity of Monolayer MoS2
• Summery
Outline
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Motivation
Kin Fai Mak, et al Phys.Rev.Lett. 105, 136805 (2010)
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Optical phenomena
Photoluminescence:
Excitonic , Free electron,…
Absorbance:
Inter-band , intra-band
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Circular dichroism
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Inversion symmetry(real space)
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Inversion symmetry(k space)
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Symmetry of band structure
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Inversion symmetry breaking& valley Hall effect
Di Xiao, et al Phys.Rev.Lett. 99, 236809 (2007).
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Gapped Graphene & Valley physics Inversion symmetry breaking& valley pumping
W.Yao, D.Xiao, Q.Niu, Phys. Rev. B 77, 235406 (2008).
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Light Emitting Diode(LED)
Electrically controlled emission polarization
W.Yao, D.Xiao, Q.Niu, Phys. Rev. B 77, 235406 (2008).
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Monolayer Transition metal dichalcogenides semiconductor
• Direct Band Gap in visible range
• Broken inversion symmetry
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Layered Compounds: Transition metal dichalcogenides ( 𝐌𝐗𝟐)
Chhowalla et al, Nature Chemistry 5, 263–275 (2013)
𝐻𝑓𝑆2: Insulator
𝑀𝑜𝑆2, W𝑆2: Semiconductor
𝑇𝑖𝑆𝑒2, 𝑊𝑇𝑒2: Semimetal
𝑁𝑏𝑆2, V𝑆𝑒2: Metal
Band Structure: DFT
14 Nature Chemistry 5, 263–275 (2013)
Symmetry & band structure
15 K. F. Mak et al., Nature Nanotech. 7, 494 (2012).
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Optical Absorbance
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Excitonic Absorbance
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Optically Induced Valley Polarization K. F. M
ak e
t al., N
atu
re N
anote
ch. 7, 4
94 (2
012).
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No Hanle effect
Zeng et al, Nature NanoTech. 7, 409 (2012).
Luminescence Polarization :
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Lattice and Orbital symmetry& Circular Dichroism
T. Cao, et al., Nature Commun. 3, 887 (2012).
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Spin-Valley coupling
K. F. Mak et al., Nature Nanotech. 7, 494 (2012).
22 Di Xiao, et al , Phys. Rev. Lett. 108,196802 (2012)
Spin-Valley coupling
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H.R, and Reza Asgari (to be submitted)
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Hamiltonian
Shun-Qing Shen, Topological Insulator, Springer(2012).
H.-Z. Lu,et al Phys.Rev.B 81, 115407(2010).
H. R, A. G. Moghaddam, R. Asgari, Phys. Rev. B 88, 085440 (2013).
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Kubo’s Formula
Wang-Kong Tse and A.H.MacDonald,Phys.Rev.B 84,205327(2011).
T. Stauber, N. M. R. Peres, and A. K. Geim,Phys.Rev.B 78,085432 (2008).
Zhou Li and J. P. Carbotte,Phys. Rev. B 86, 205425(2012).
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Optical spin/valley Conductivity
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Optical Hall Conductivity
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Optical Longitudinal Conductivity
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Xiao’s Model
Di Xiao, et al , Phys. Rev. Lett. 108,196802 (2012)
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Numerical Parameter
037.0 mme 044.0 mmh
05.0 mme 05.0 mmh
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Static limit
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Static limit: the effect of Beta
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Dynamical Hall Conductivity
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Dynamical Longitudinal Conductivity
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Optical Conductivity(mass asymmetry)
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Tuning the spin splitting by Fermi energy
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Circular Polarization
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Optical Transmission
A. C.-Gomez et al, Private communication
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Summary
• Inversion symmetry breaking leads to valley contrasting physics
• Circular dichroism in monolayer MoS2 can be describe by intrinsic optical conductivity
• Charge, spin, and valley Hall effect
• Optical valley pumping
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Thank You!