the nano-textured phase of 1t-tas2 probed by optical...

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

Acknowledgments

UKF 65/10 http://frustrated-electrons.ifs.hr/