Femtosecond RealTime studies of Lu5Ir4Si10 Charge Density Wave Compound

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Femtosecond Real-Time studies of Lu5Ir4Si10
Charge Density Wave Compound

• Andrej Tomeljaka,1, Jure Demsara,
• Antoinette J. Taylorb,
• Federicca Gallic, John A. Mydoshc

aJoef Stefan Institute, Jamova 39, Ljubljana,
Slovenia bLos Alamos National Lab, Los Alamos,
NM 87545, USA cKamerlingh Onnes Laboratory,
University of Leiden, Leiden, The Netherland 1
andrej.tomeljak_at_ijs.si
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CDW materials

• Modulation of the charge density
• Occurrence in low dimensional solids
• Nesting of the Fermi surface
• Energy gap in the single particle excitation
  spectrum

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Motivation
YBa2Cu3O6.9
J.Demsar et al., Phys. Rev. B. 61, 1477 (2000).
J.Demsar et al., Phys. Rev. Lett. 83, 800 (1999).
K0.3MoO3
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Lu5Ir4Si10

• TCDW 83 K
• Strong interchain coupled system with first order
  CDW transition
• Only partial gapping of the Fermi surface
• Weak CDW effect
• Superconducting at T lt 3.9 K.

B. Becker et al., Phys. Rev. B 59, 72667269
(1999).
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Experiment
probe
E
excitation
Dt
sample
CDW
c
a
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Experiment
E
Dt
probe
sample
excitation
CDW
c
a
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Femtosecond time resolved spectroscopy

• Observation of reflectivity relaxation after
  short laser pulse (20 fs) excitation.
• Initial relaxation of the material within 10-100
  fs.
• Further relaxation depends strongly on the low
  lying electron spectrum.
• The technique very sensitive to the opening of a
  gap in the single particle excitation spectrum

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Experimental details

• Small signals ?R/R 10-6
• Averaging, mode-locking the signals
• Linear regime
• Heating due to laser illumination estimated to
  20 K and accounted for

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Offset
Calculated data from Tediosi et al., to be
published.
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Offset
Calculated data from Tediosi et al., to be
published.
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Oscillations
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Oscillations
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Oscillations
K0.3MoO3
1T-TaS2
2H-TaSe2
J. Demsar et al., Phys. Rev.B 66, 041101(R)
(2002).
J.Demsar et al., Phys. Rev. Lett. 83, 800 (1999).
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Picosecond component
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Picosecond component
Groeneveld et al, Phys. Rev. B 51, 11433 (1995).
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Picosecond component
J. Demar et al.
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Picosecond component
2D 400 K
J. Demar et al.
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Conclusions

• First studies of carrier relaxation dynamics in
  Lu5Ir4Si10
• Despite the small changes in the low energy
  electronic structure (change in resistivity only
  30) and metallic behavior at low T, signatures
  of CDW modulation are observed in real time
  dynamics response.
• The long nanosecond dynamics can be explained in
  terms of bolometric response
• Oscillatory component (strongly damped) is
  attributed to the amplitude mode of the CDW
• The picosecond decay dynamics shows anomalous
  temperature dependence below TCDW. The behavior
  is consistent with the relaxation across the CDW
  gap. The gap magnitude was estimated to be 2D
  400K 35 meV.

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J. B. Betts et al., Phys. Rev. B 66, 060106(R)
(2002)
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Lu5Ir4Si10
Y.-K. Kuo et al., Phys. Rev. B 67, 195101 (2003).
Y.-K. Kuo et al., Phys. Rev. B 67, 195101 (2003).
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Lu5Ir4Si10
J. B. Betts et al., Phys. Rev. B 66, 060106(R)
(2002)
B. Becker et al., Phys. Rev. B 59, 72667269
(1999).
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References

• J.Demsar et al., Phys. Rev. Lett. 83, 800 (1999).
  
• J.Demsar et al., Phys. Rev. B. 61, 1477 (2000).
• J. B. Betts et al., Phys. Rev. B 66, 060106(R)
  (2002).
• Y.-K. Kuo et al., Phys. Rev. B 67, 195101 (2003).
• B. Becker et al., Phys. Rev. B 59, 72667269
  (1999).
• H. F. Braun, Acta Crystallogr., Sect. B Struct.
  Crystallogr. Cryst. Chem. 36, 2397 (1980) J.
  Less-Common Met. 100, 105 (1984).
• J. Demsar et al., Phys. Rev.B 66, 041101(R)
  (2002).

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Experimental details

• Laser Mode-locked Ti-sapphire
• 800 nm (1.55 eV)
• 20 fs pulses
• 80 MHz repetition
• 70 (30) µm pump (probe) focus
• Lock-in with 100 kHz modulation
• Pump (probe) power 30 (2) mW ? excitation
  density j 40 µJ/cm2.