vibrational quantum transport

Vibrational Quantum TransportPhD defence June 4th, 2010Mads Engelund

Supervisors:Antti-Pekka JauhoMads Brandbyge

•Introduction•Basic approach•Results

DTU Nanotech, Technical University of Denmark2

DTU Nanotech, Technical University of Denmark

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New transistor approaches

Song and Lee, Nature, 462, 1039 (2009)http://www.sciencedaily.com/releases/2009/12/091223133343.htm


Lin et al., Science, 327, 662 (2010)

New transistor approaches

Song and Lee, Nature, 462, 1039 (2009)http://www.sciencedaily.com/releases/2009/12/091223133343.htm


Heat dissipation


Heat dissipationDoing work

Flickr.com/mikebaird


Heat dissipationDoing work

Flickr.com/mikebaird

Overheating

Flickr.com/mikebairdDTU Nanotech, Technical University of Denmark7

Ralph Group, Cornell University, http://people.ccmr.cornell.edu/~ralph/projects/emig_movies/


Heat


Heat


=Energy we’ve lost track of

5

Heat


=Energy we’ve lost track of

Public domain

5


Vibrations =main storage of heat

Wikimedia commons

Macroscopic suspended beam

Microscopic graphene edge

6

Heat flow on different scales


Sierra Pacific Innovations: ww.x20.org




IEEE Spectrum: Carbon Nanotubes Takes the Heat of Chips, Bryan Christie Design





Wikimedia Commons





Wikimedia Commons

Wikimedia Commons



ElectronicsPhotonicsVibronics?

10 DTU Nanotech, Technical University of Denmark


Physical Review Letters, 104, 083901(2010)

Saser



Science, 314, 5802, 1121-1124(2009)

Thermal wave guide and rectifier

Physical Review Letters, 104, 083901(2010)

Saser



Measurements on vibrations

11



Raman Spectroscopy

Nano Lett., 8-3, 919-924(2008)‏

11



Raman Spectroscopy

Nano Lett., 8-3, 919-924(2008)‏

Thermal probing

J. of App. Phys., 105, 104306 (2009)

11

Ab-initio• Data-> Basic principles -> model

EmpiricalData -> model


Ab-initio• Data-> Basic principles -> model

EmpiricalData -> model

18

DFTAccurate tool but only app. 1000 atoms



Gold chains

13


Gold chains

Eur. Phys. J. D, 16, 395(2001)‏

Simple structure

13


Gold chains

Eur. Phys. J. D, 16, 395(2001)‏

Simple structure

13

Clear inelastic signal

Phys. Rev. Lett., 88, 216803(2002)‏


The dynamical matrix

14


The dynamical matrix

14

Equation of motion (Newton’s 2.)

Green’s function


DOS

Green’s function


Leads

DOS


Calculating the Self-Energy


The Surface Green’s function

k

0

0

Discrete modes vs. broadened modes

Frequency/Energy

Den

sity

of S

tate

s


Time

Am

plitu

de

Frequency/Energy

Den

sity

of S

tate

s



Q-factors

17


Q-factors

17

Am

plitu

de

0

Time

High Q-factor

Low Q-factor

Programming


8000 lines

getGreensFunction(system)

getSelfEnergy(system)getDynamicalMatrix(system)

getFCMatrix(system)

getFCMatrix(surface)

getlFCMatrix(crystal)

Read SIESTAResultRead

SIESTAResultRead

SIESTAResult

getSelfEnergy(surface)

getUnpertubedDynamicalMatrix(surface)

getSurfaceGreensFunctionPrDiffVector(surface)

getFCMatrix(surface)

getDynamicalMatrix(surface)

Programming


8000 lines


–Gold Chains–Graphene edges



Study of gold chains

21


Study of gold chains

21

Eur. Phys. J. D, 16, 395(2001)‏

24

Amplitude in chain

High

Hig

hLo

wQ

-fact

or

24

Amplitude in chain

High Low

Hig

hLo

wQ

-fact

or


Length


Type of lead


Gold Chains


Gold Chains

•Instances of very low damping


Gold Chains

•Instances of very low damping

Frederiksen et al., Phys. Rev. B, 75, 205413(2007)


Gold Chains

•Instances of very low damping•Sensitivity

Frederiksen et al., Phys. Rev. B, 75, 205413(2007)


Gold Chains

•Instances of very low damping•Sensitivity

quantrans.org/introduction


–Gold Chains–Graphene edges


www.als.lbl.gov/pics/154graphene01.png



www.technologyreview.com/files/11636/graphene_x220.jpg


http://www.technologyreview.com/files/




Lin et al., Science, 327, 662 (2010)





An interesting experiment

*Jia et al., Science, 2009, 323, 1701

25


An interesting experiment

*Jia et al., Science, 2009, 323, 1701

elec

troni

c cu

rren

t

25

02/28/2010Armchair edges in grapheneDTU Nanotech, Technical University of Denmark33

The quick description


Vibrations


Vibrations

Electrons


Vibrations

Electrons

?

e

Bia

s

Pot

entia

l ene

rgy

of e

lect

rons


Graphene Edges


Graphene Edges

*Jia et al., Science, 2009, 323,


Graphene Edges


Graphene Edges

Bye, bye armchair dimer

Conclusions


Phys. Rev. Lett., 88, 216803(2002)‏

Conclusions

• Vibrations sensitive to everything


Phys. Rev. Lett., 88, 216803(2002)‏

Conclusions

• Vibrations sensitive to everything• Importance of ab-initio


Conclusions

• Vibrations sensitive to everything• Importance of ab-initio• Control of matter


Science, 2009, 323, 1701

Conclusions

• Vibrations sensitive to everything• Importance of ab-initio• Control of matter


Science, 2009, 323, 1701

Phys. Rev. Lett., 104,


Background-Theoretical Modeling of Vibrational Properties



Non-conservative ForcesDundas et al., Nat. Nano., 4, 99-103(2009)‏




DynamicsMcEniry et al., Phys. Rev. B, 035446(2008)‏




Anharmonic TransportMingo,

Phys. Rev. B, 125402(2006)‏

DynamicsMcEniry et al., Phys. Rev. B, 035446(2008)‏

Vibrational Quantum TransportPhD defence June 4th, 2010Mads Engelund

Supervisors:Antti-Pekka JauhoMads Brandbyge

vibrational quantum transport

Education