Leonardo Degiorgi Laboratorium für Festkörperphysik ETH Zürich, Switzerland

Infrared and Raman study of the charge-density-wave state in the rare-earth

polychalcogenides RTen

Leonardo DegiorgiLaboratorium für Festkörperphysik

ETH Zürich, Switzerland

Motivation

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➠ Charge ordering in low dimensions (CDW, stripes, checkerboard)➠ Impact of charge ordering on the lattice dynamics➠ Interplay between electronic and phononic degrees of freedom➠ Role played by the electron-phonon coupling➠ Fermi surface instabilities (nesting)

DiMasi et al., Phys. Rev. B52, 14516 (1995)

RTe2

R2Te5

The Rare-Earth Tellurides RTen (n=2, 2.5 and 3)

RTe3

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Reflectivity and Optical Conductivity

10-3 10-2 10-1 100 101

101 102 103 104

0

20

40

60

80

100

Photon energy [eV]

Ref

lect

ivity

[%]

MetalInsulator

[cm-1]

Photon Energy (eV)

10-3 10-2 10-1 100 101

101 102 103 104

0

5

10

15

Photon energy [eV]

1 [x10

3 S /

cm]

MetalInsulator

[cm-1]

1(

) (

cm)-1

Photon Energy (eV)

http://www.solidphys.ethz.ch/spectro/

Sacchetti et al., Phys. Rev. B74, 125115 (2006)

Optical Reflectivity of RTe3

101 102 103 104 1050.0

0.2

0.4

0.6

0.8

1.0

Frequency (cm-1)

Ref

lect

ivit

y

La

RTe3

101 102 103 104 1050.0

0.2

0.4

0.6

0.8

1.0

Frequency (cm-1)

Ref

lect

ivit

y

LaCe

RTe3

101 102 103 104 1050.0

0.2

0.4

0.6

0.8

1.0

Frequency (cm-1)

Ref

lect

ivit

y

LaCeNd

RTe3

101 102 103 104 1050.0

0.2

0.4

0.6

0.8

1.0

Frequency (cm-1)

Ref

lect

ivit

y

LaCeNdSm

RTe3

101 102 103 104 1050.0

0.2

0.4

0.6

0.8

1.0

Frequency (cm-1)

Ref

lect

ivit

y

LaCeNdSmGd

RTe3

101 102 103 104 1050.0

0.2

0.4

0.6

0.8

1.0

Frequency (cm-1)

Ref

lect

ivit

y

LaCeNdSmGdTb

RTe3

101 102 103 104 1050.0

0.2

0.4

0.6

0.8

1.0

Frequency (cm-1)

Ref

lect

ivit

y

LaCeNdSmGdTbDy

RTe3

0 2.103 4.103 6.103 8.103 1.1040.6

0.7

0.8

0.9

1.0

Frequency (cm-1)R

efle

ctiv

ity

LaCeNdSmGdTbDy

RTe3

Sacchetti et al., Phys. Rev. B74, 125115 (2006)

Plasma Frequency and Single Particle Peak in RTe3

4.30 4.35 4.40

6.0.103

8.0.103

1.0.104

1.2.104

Lattice constant (Å)

p (cm -1 )

Dy

Tb

Gd

Sm

Nd

Ce

La

RTe3

4.30 4.35 4.40

6.0.103

8.0.103

1.0.104

1.2.104

Lattice constant (Å)

p (cm -1 )

Dy

Tb

Gd

Sm

Nd

Ce

La

RTe3

4.30 4.35 4.400

2000

4000

6000

Lattice constant (Å)

SP (cm -1 )

RTe3

LaCe

Nd

Sm

Gd

Tb

Dy

4.30 4.35 4.400

2000

4000

6000

Lattice constant (Å)

SP (cm -1 )

RTe3

LaCe

Nd

Sm

Gd

Tb

Dy

Pressure Dependence of R() in CeTe3

Sacchetti et al., Phys. Rev. Lett. 98, 026401 (2007)

CDW Gap: Applied versus Chemical Pressure

Dependence

X-ray experiment at ESRF

Raman Scattering

Ek

E2

E1

ħωħω’

E1

E2ħω’ħω

Stokes Anti-Stokes

Raman Scattering in RTe3:Chemical versus Applied Pressure

Petzelt and Dvorak, J. Phys. C9, 1571 (1976)

Order Parameter versus Integrated Intensity of the Raman Modes in RTe3

4.30 4.35 4.400.00

0.02

0.04

0.06

0.08

0.00

0.01

0.02

0.03

0.04

Lattice constant (Å)

p2 /( p2 +S

SP 2 )

n CD

W

/n NS

nCDW/nNS

RTe3Dy

Tb

Gd

Sm

Nd

Ce

La

1 ( ) ( cm

)

-1

Frequency (cm-1)

2.103 5.103 104 2.104103

104

104

CeTe3

LaTe3

104

104

104

104

104NdTe3

SmTe3

GdTe3

TbTe3

DyTe3-1

-1.2

-1

-1.3

-1.5

-1.7

-1.2

2.2

3

Conclusions and Future Outlook

1 ( ) ( cm

)

-1

Frequency (cm-1)

2.103 5.103 104 2.104103

104

104

CeTe3

LaTe3

104

104

104

104

104NdTe3

SmTe3

GdTe3

TbTe3

DyTe3-1

-1.2

-1

-1.3

-1.5

-1.7

-1.2

2.2

3

Fermi Surface Gapping

Tomonaga-Luttinger Liquid

Equivalence between Chemical and Applied Pressure

Phonon Dispersion and Kohn Anomaly

4.30 4.35 4.400.00

0.02

0.04

0.06

0.08

0.00

0.01

0.02

0.03

0.04

Lattice constant (Å)

p2 /( p2 +S

SP 2 )

n CD

W

/n NS

nCDW/nNS

RTe3Dy

Tb

Gd

Sm

Nd

Ce

La

Acknowledgements

Lavagnini Sacchetti

Theory

T. Giamarchi(University of Geneva)R. Monnier(ETH Zurich)B. Delley(PSI)

Pfuner

Experiment

A. PerucchiE. ArcangelettiL. BaldassarreM. BaldiniD. Di CastroP. PostorinoS. Lupi(University La SapienzaRome and ELETTRA Trieste)

Samples

I.R. FisherN. RuY.K. ShinJ.-H. Chu(Stanford University)