Tuning charge density wave glass transition by introducing lattice disorder ECRYS 2011 D. Dominko,...
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Tuning charge density wave glass transition by introducing lattice disorder ECRYS 2011 D. Dominko, K. Biljaković, D. Starešinić Institute of Physics, Zagreb, Croatia M. Jakšić Institute Ruđer Bošković, Zagreb, Croatia P. Lunkenheimer, A. Loidl University of Augsburg, Germany
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Transcript of Tuning charge density wave glass transition by introducing lattice disorder ECRYS 2011 D. Dominko,...
Tuning charge density wave glass transition by introducing lattice disorder
ECRYS 2011
D. Dominko, K. Biljaković, D. StarešinićInstitute of Physics, Zagreb, CroatiaM. JakšićInstitute Ruđer Bošković, Zagreb, CroatiaP. Lunkenheimer, A. LoidlUniversity of Augsburg, Germany
Scope
introduction glass transition sample preparation transport properties dielectric response discussion conclusion
Introduction- pinning Friedel oscillations around
impurity site pin CDW phase domain structure
Plot 1 r
CDW
Friedel
CDW phase bends to minimise pinning energy on two neighbour impurity sites
change of wave vector q~p-ntwo degenerate polarisations around impurity site simplified scheme:
Introduction- response to external field overdamped response two (three) processes
- high T ~ freezes at 40 K determines glass
transition temperature - below 60 K both relaxation times
follow resistivity polarisation change
governed by free carriers?
~~viscosity?
1/T (1/K)0.00 0.01 0.02 0.03 0.04 0.05
(s
)
10-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
D
C (
m)
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
DC
TaS3
E=800 K
E=300 K
Introduction- freezing criterionFree carrier number follows activation law
increase of viscosity process slows down and freeze when reaches 100 s
(TG determined by fit)when exactly does it happen?
Tke
BelenTn /0)(
domain density: 1015 cm-3
atat T Tgg
1 e1 e per per domdomainain
freezing criterion?
ne(Tg )~1015 e/cm3
QTSD~1015
electrons/cm3 if so - polarisation is governed by free carriers screening tested by reducing domain size
Sample preparation
irradiation by H+ ions sample thickness <10 m 2 MeV, Van der Graaf at IRB mainly just vacancies and
interstitials uniform up to 10 m (range: 30 m) recombination (annealing)?
assumption: number of long living defects is proportional to the number right at the beginning
1/T (1/K)
0.003 0.005 0.007 0.009 0.011 0.013
R/R
RT
1
10
100
1000
72240110440
defects (ppm)
1/T (1/K)0.004 0.005
R/R
RT
1
10
T (K)
60 80 100 120 140 160 180 200E
T (
V/c
m)
1
10
72240110440
Results - transport transition smearing el unchanged minimum in ET is
disappearing limiting curve for
high dosage
103
104
105
106
107
108
0.01
0.02
0.03
0.04
0.05
Results – dielectric response
’’(f,T)
pure
Results – dielectric response
’’(f,T)
104
105
106
107
108
109
0.0060.008
0.0100.012
0.0140.016
0.0180.020
0.022
2.2 ppm
Results – dielectric response
104
105
106
107
108
109
0.0060.008
0.0100.012
0.0140.016
0.0180.020
0.022
’’(f,T)
67 ppm
Results – dielectric response
1e+4
1e+5
1e+6
1e+7
1e+8
1e+9
0.0060.008
0.0100.012
0.0140.016
0.0180.020
0.022
’’(f,T)
220 ppm
101
102
106
107
doping (ppm)
190 K110 K50 K
1/n
Results – dielectric response higher domain
density reduction of
proces amplitude hi T: ~ 1/n process
unchanged0 50 100 150 200 250
105
106
107
T [K]
6.7
22.3
4067
220
440
proces proces
100 kHz
Results – dielectric response
1/T (1/K)
0.003 0.006 0.009 0.012 0.015
(s
)
10-9
10-8
10-7
10-6
10-5
2.2 ppm22 ppm67 ppm220 ppm
1/T (1/K)
0.006 0.008 0.010 0.012 0.014 0.016
(s
)
10-8
10-7
10-6
10-5
2.2 ppm22 ppm67 ppm220 ppm
a)
at high T- minimum in pure ones –
flattening activation energy
increases
0 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035
10-10
10-5
100
1/T (1/K)
(s
)
2.213.567220fit 2.2fit 13.5fit 67fit 220
Tg
Eact increases above el
100
101
102
103
800
900
1000
1100
1200
defects (ppm)
Eac
t (K
)
100
101
102
103
10-12
10-11
10-10
defects (ppm)
0 (
s)
Discussion – fit parameters
1/n
0 reaches phonon frequencies
=0(n)e-(n)/T, (TG)=100 s
Tg increases electron density
increases 2 orders of magnitude on interval Tg(ni)
consistent with radiation level!
100
101
102
103
30
32
34
36
38
40
defects (ppm)
Tg (
K)
Discussion – fit parameters- TG
1/Tg (1000/K)26 27 28 29 30 31 32 33 34
n (p
pm)
1
10
100
1000
n~exp(-700/TG)
n-1/Tg has activational behavior with =el!
electron
n
nTn
i
Gfc 1)(
GB
el
TkGfc eTn
~)(
Discussion - threshold low T part of ET “spoons” detaches from
the most irradiated sample (~e-T/50 K) higher dosage -> higher the crossover
temperature Tcross
exponential ET cross ~ e-Tcross/T0 with T0=18 K same T0 as found for ET(T) bellow 100 K in
pure samples* *Itkis, Nad and Monceau, JPCM 1990
T (K)
60 80 100 120 140 160 180 200
ET (
V/c
m)
1
10
72240110440
process insensitive to doping level is not governed by the carrier number alone any
more – domain cooperativity slows it down even more?
TG tuned by defect number having one electron per domain activation temperature for ni(TG) is 700 K- follows
electron count n(T)! high T minimum in appears after irradiation pinning resonance increases? at high T- ET insensitive to doping level, at low T it
increases
Conclusions – glass
Attention!
Thank you for your attention!
Low temperature state- Coulomb stiffening prefers constant phase- only local distortions allowed
- CDW chain cut with topological defects (solitons)
- TLS - like - bound e- states at impurity
Bound states
Tutto, Zawadowski PRL ‘85
Results - transport
defects (ppm)
10 100
ET (
V/c
m)
1
10
180 K150 K110 K80 K
0.430.52
0.16
ET-n power low, but weaker than ~n
