the nano-textured phase of 1t-tas2 probed by optical...
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The nano-textured phase of 1T-TaS2 probed by optical conductivity
K. Velebit, P. Popčević, A. Smontara, H. Berger, L. Forró, M. Dressel, N. Barišić
Laboratory for the physics of transport phenomena Institute of Physics, Zagreb, Croatia
http://condensed-matter.ifs.hr/
Electronic States and Phases Induced by Electric or Optical Impacts
Orsay, 2012
z
y
x
unit cell Ta
S
1T-TaS2 crystal structure
Pure 1T-TaS2
metal CCDW NCCDW ICCDW
Sipos et al., Nature Mat., 2318 (2008).
200 TaS2 unit cells
Spijkerman 1997 PRB X ray
~200 TaS2 unit cells
1T-TaS2
NC-CDW state
Thompson, Phys. Rev. B (1994)
Optics in Mott phase 1T-TaS2
Gasparov et al., PRB 66, 094301 (2002).
NCCDW phase
CCDW + Mott phase
Perfetti et al., PRB 71, 153101 (2005).
NC-CDW state
1T-TaS2
C-CDW Mott
Metallic
SC
Sipos et al., Nature Mat., 2318 (2008).
Suppression of Mott state and emergence of superconductivity
IR reflectivity of pure 1T-TaS2 under pressure
NCCDW
CCDW + Mott
Kezsmarki et al., PRB 76, 205114 (2007).
0 50 100 150 200 250 300
0
20
40
60
Doped 1T-TaS2
(T)/
(29
0K
)
T (K)
Pure 1T-TaS2
1T-TaS2 – doped vs. pure NCCDW phase CCDW/Mott phase
100 1000 100000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
pure 1T-TaS2
Re
fle
ctivity
Frequency (cm-1)
290K
200K
200K_up
150K
100K
50K
23K
100 1000 100000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
doped 1T-TaS2
Re
fle
ctivity
Frequency (cm-1)
290K
200K
150K
100K
50K
23K
IR reflectivity of pure vs. doped 1T-TaS2
NCCDW
CCDW + Mott
100 1000 100000
500
1000
1500
2000
2500
3000
pure 1T-TaS2
1(
cm
)-1
Frequency (cm-1)
290K
200K
200K_up
150K
100K
50K
23K
Optical conductivity σ1(ω) of pure vs. doped 1T-TaS2
100 1000 100000
500
1000
1500
2000
2500
doped 1T-TaS2
1 (
cm
)-1
Frequency (cm-1)
290K
200K
150K
100K
50K
23K
Spectral weight of pure vs. doped 1T-TaS2
100 1000 1000010
4
105
106
107
108
109
pure 1T-TaS2
SW
Frequency (cm-1)
290K
200K
200K_up
150K
100K
50K
23K
100 1000 1000010
4
105
106
107
108
109
doped 1T-TaS2
SW
Frequency (cm-1)
290K
200K
150K
100K
50K
23K
Summary and outlook
• NCCDW phase in doped 1T-TaS2 measured optically to low temperatures
• Doped 1T-TaS2 allows us to study the NCCDW phase down to very low temperatures at ambient pressure
• We observe a wide Drude contribution, indicating high scattering, and a loss of spectral weight with decreasing temperature
• Insulating/metallic pattern picture is consistent with our measurements
