University of Regensburg
Martin Gmitra , Denis Kochan, Petra Högl and Jaroslav Fabian
Electronic structure of grapheneon transition-metal dichalcogenides
Oct. 05.-07. 2015internal SFB-workshop in Abbey Frauenwörth
Frauenchiemsee
DFG SFB 689
University of Regensburg
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Transition metal dichalcogenides essentialsMX2 :: [M = metal atom (Mo, W, …) ; X = chalcogen atom (S, Se, Te)]
Space Group: P 63/mmc
atomically thin semiconductors
K.F. Mak et al., PRL 105, 136805 (2010)Molybdenite (MoS2)
University of Regensburg Transition metal dichalcogenides essentialsMX2 :: [M = metal atom (Mo, W, …) ; X = chalcogen atom (S, Se, Te)]
Space Group: P 63/mmc
review: A. Kormányos et al., 2D materials 2, 022001 (2015)
bulk single layer (no inversion)
d-character dominates optical edges
spin-orbit coupling emerges in optics
University of Regensburg Optical properties of TMDChelicity resolves ...
● valley polarization H. Zeng et al., Nat. Nanotech. 7, 490 (2012)
● coupled spin and valleys (valleytronics) P. Xiao et al., PRL 108, 196802 (2012) ● spin, valley and layer pseudospin coupling
(intra/inter layer trions) X. Xu et al., Nat. Phys. 10, 343 (2014)
University of Regensburg Graphene on TMDCheterostructure
www.quantum-espresso.org
Method used :: Density Functional Theory (DFT) calculations
University of Regensburg Band structure of TMDC/graphene heterostructuresproximity orbital effects
M. Gmitra et al., arXiv: 1510.00166
University of Regensburg Trivial and inverted Dirac bandsproximity spin-orbit coupling effect
M. Gmitra et al., arXiv: 1510.00166
University of Regensburg Model for low energy bandsdefinition & low energy model fit
M. Gmitra, J. Fabian, arXiv: 1506.08954, PRB in pressM. Gmitra et al., arXiv: 1510.00166
University of Regensburg Graphene zigzag nanoribbon on WSe2quantum spin Hall effect
● inside the gap – topological helical edge states● outside the gap – half-topological states
University of Regensburg Effect of transverse electric field on band offsetDirac massless electrons coupled with conventional 2d electrons
University of Regensburg
All optical detection of spin tunneling and accumulation using magneto-optical Kerr effect.
Graphene on TMDC :: platform for optospintronics
Optical spin injection scheme employing Hanle effect.
M. Gmitra, J. Fabian, arXiv: 1506.08954, PRB in press
University of Regensburg Concluding remarks
ACKNOWLEDGMENTS:
DFG SFB 689
graphene on TMDC serves as● a platform for optospintronics● coupled system of Dirac massless and 2D conventional electrons● new “half” topological states at single edge channel● robust quantum spin Hall effect
M. Gmitra, J. Fabian, Graphene on transition-metal dichalcogenides: a platform for proximity spin-orbit physics and optospintronics arXiv: 1506.08954, PRB in press
M. Gmitra, D. Kochan, P. Högl, J. Fabian,Trivial and inverted Dirac bands, and emergence of quantum spin Hall states in graphene on transition-metal dichalcogenidesarXiv: 1510.00166