130712 dorothee socgraphene
Post on 04-Jun-2018
223 Views
Preview:
TRANSCRIPT
-
8/13/2019 130712 Dorothee SOCgraphene
1/12
Colossal enhancement of spin orbit couplingin weakly hydrogenated graphene
J. Balakrishnan, G. K. W. Koon, M. Jaiswal, A. H. Castro Neto, B. zilmazNature 9, 284 (2013)
-
8/13/2019 130712 Dorothee SOCgraphene
2/12
Outline Spin orbit in graphene
Spin Hall effect and measurement
Fabrication of the samples
Measurements at RT and 4K
Conclusion
12.07.2013 2
-
8/13/2019 130712 Dorothee SOCgraphene
3/12
Spin orbit coupling in graphene
12.07.2013 Konschuh, PRB 82 245412 (2010); J. Balakrishnan, DOI:10.1038/NPHYS2576 3
Curved graphene:
SpinAtomic spin orbit strength, l=s,p,d..SO gapStates at K/K pointStates at A/B point
Energy of orbital
V Hopping parameter
with
Flat graphene:
-
8/13/2019 130712 Dorothee SOCgraphene
4/12
Spin Hall effect
12.07.2013 J. E. Hirsch, PRL 83, 9 (1999); J. Balakrishnan, DOI:10.1038/NPHYS2576 4
-
8/13/2019 130712 Dorothee SOCgraphene
5/12
Sample fabrication Graphene exfoliation
EBL for contacts
EBL for Hall bar
Coating of sample with HSQ
EBL exposure of HSQ
12.07.2013 J. Balakrishnan, G. K. W. Koon, M. Jaiswal, A. H. Castro Neto, B. zyilmaz, DOI:10.1038/NPHYS2576 5
-
8/13/2019 130712 Dorothee SOCgraphene
6/12
Calculation of impurity concentration
12.07.2013 J. Balakrishnan, G. K. W. Koon, M. Jaiswal, A. H. Castro Neto, B. zyilmaz, DOI:10.1038/NPHYS2576 6
Hydrogenation =
Dose ~
-
8/13/2019 130712 Dorothee SOCgraphene
7/12
RNL, Rohmic and measurements
12.07.2013 J. Balakrishnan, G. K. W. Koon, M. Jaiswal, A. H. Castro Neto, B. zyilmaz, DOI:10.1038/NPHYS2576 7
W Width of sampleL Length of sample Resistivity
-
8/13/2019 130712 Dorothee SOCgraphene
8/12
In-plane magnetic field dependence T=4 K
12.07.2013 J. Balakrishnan, G. K. W. Koon, M. Jaiswal, A. H. Castro Neto, B. zyilmaz, DOI:10.1038/NPHYS2576 8
Sample hydrogentation: 0.01%
Gyromagnetic ratio
Spin diffusion constantSpin precession lengthWidth of sampleLength of sampleSpin Hall coefficentSpin dephasing time
-
8/13/2019 130712 Dorothee SOCgraphene
9/12
Width and length dependence of RNL, RT
12.07.2013 J. Balakrishnan, G. K. W. Koon, M. Jaiswal, A. H. Castro Neto, B. zyilmaz, DOI:10.1038/NPHYS2576 9
=1 m
H = 0.02%, =1600cm2/(VS)H = 0.05%, =900cm2/(VS)
H = 0.01%, =1400cm2/(VS)
~
-
8/13/2019 130712 Dorothee SOCgraphene
10/12
Determination of s and SO
12.07.2013 J. Balakrishnan, DOI:10.1038/NPHYS2576: 10
Elliott-Yafet scattering
At adatom (H), out of plane bending: and orbital mixing!
SO becomes first order effect
Fermi energy
Momentum relaxation timeSO coupling strength
-
8/13/2019 130712 Dorothee SOCgraphene
11/12
Conclusion Increase of SOE by partial hydrogenation of graphene
Measurement of SHE in graphene using SOE
Oscilation of RNL in dependence of BII
Clear dependence of RNL with the sample width andlength
12.07.2013 11
-
8/13/2019 130712 Dorothee SOCgraphene
12/12
Dresselhaus and Rashba terms
12.07.2013 12J. Balakrishnan, DOI:10.1038/NPHYS2576:
Starting Hamiltonian:
Dresselhaus term:
Rashba term:
top related