Post on 17-Jan-2016
Galvanomagnetic effects in electron-doped
superconducting compounds
D. S. Petukhov1, T. B. Charikova1, G. I. Harus1, N. G. Shelushinina1,
V. N. Neverov1, O. E. Petukhova1, A. A. Ivanov2
1Institute of Metal Physics UB RAS, Ekaterinburg2Moscow Engineering Physics Institute, Moscow
TopicsIntroduction
The aim of the work
Experiment: samples, experimental equipment
Results
Conclusion
2
IntroductionThere is no universally accepted mechanism
of the superconducting state formation in HTSC
Studies of galvanomagnetic phenomena provide important information about the
behavior of carriers in the normal state of HTSC
Properties of the superconductor in the normal state determine its properties in the
superconducting state
There are questions concerning the physical picture of normal and mixed state of HTSC
Clarify the features of the superconducting state in HTSC
3
IntroductionVarious researchers have found features of the behavior Hall resistivity dependencies on the
temperature and magnetic field.
YBa2Cu3O7 Nd1.85Ce0.15CuO4+δ
Hagen S. J. PRB V.47 P.1064 (1993) 4
Introduction
K. Jin PRB V.78 P. 174521 (2008)
Pr2-xCexCuO4La2-xCexCuO4Y. Dagan PRB V.76 P. 024506
(2007)
5
Introduction
A. Casaca PRB V.59 P. 1538 (1999)
YBa2Cu3O7
There is a sign change in
the mixed state.
A similar anomaly is
observed in many materials.
Trend dependence of the
Hall resistance does not
depend on the sign of the
majority charge carriers.
The presence or absence of
anomaly depends on the
purity of the sample.6
IntroductionThe sign change of the Hall coefficient in the mixed
state can be explained:
Thermoelectric models
Models of Nozieres-Vinen and Bardeen-Stephen
Pinning models
Two-band/two-gap models
7
Hall coefficient in the normal state
Nie Luo arXiv:cond-mat/0003074v2, P. 1 (2000)8
Shubnikov de Haas oscillations
M.V. Kartsovnik New Journal of Physics V13, P. 1-18 (2011) 9
Nd2-xCexCuO4+δ
ARPES data
Armitage N.P. Rev. Mod. Phys. V82, P. 2421 (2010)Armitage N.P. PRL V88, P. 257001 (2002)Matsui H. PRL V94, P. 047005 (2005)Matsui H. PRL V75, P. 224514 (2007)
10
Nd2-xCexCuO4+δ
The aim of the work
The aim of the work was to investigate magnetic field dependence of the resistivity and Hall effect of electron-doped superconductor in the normal and mixed state, in order to study the dynamics of Abrikosov vortices in the resistive state in the electron-doped cuprate superconductor.
11
Experiment: the samples
Ivanov A.A., Galkin S.G., Kuznetsov A.V. et al., Physica C, V. 180,P. 69 (1991)12
In the experiments, we used single-crystal films Nd2-xCexCuO4+δ/SrTiO3 (x = 0.15; 0.17; 0.18) with orientation (001). The thicknesses of the films were 1200-2000 Å (x = 0.15), 1000 Å (x = 0.17) and 3100 Å (x = 0.18). The films were subjected to heat treatment (annealing) under various conditions.
Optimal doped region (х=0.15):□the optimally annealing in the vacuum(60 min, Т =
780°С, р = 10-2 mmHg); □the non-optimally annealing in the vacuum(40 min,
Т = 780°С, р = 10-2 mmHg);□As grown (without annealing); Overdoped region (х=0.17):□ the optimally annealing in a vacuum ( Т = 780°С,
р = 10-5 mmHg);Overdoped region (х=0.18):□ the optimally annealing in a vacuum (35 min, Т =
600°С, р = 10-5 mmHg).
The measurement equipmentHall effect measurements were carried out with 4-contact method
in the solenoid, "Oxford Instruments" (IMP UD RAS) and SQUID-magnetometer MPMS XL firm Quantum Design (IMP UD RAS) in magnetic fields up to 90 kOe at the temperature of Т = (1.7 – 4.2) К .
13
Results: Hall coefficient in the normal state (T=4.2K B=9T)
0,00 0,05 0,10 0,15 0,20 0,251E-6
1E-4
0,01
1
RH>0
|RH| (
cm3 /C
)
x
RH<0
~1/x
14
Charikova T. B., Physica C, V. 483 ,P. 113 (2012)
Dependences of the Hall coefficient on the magnetic field for optimally
annealing Nd2-xCexCuO4+δ x=0.15, 0.17, 0.18
0 20 40 60 80 100
-2,0
-1,5
-1,0
-0,5
0,0
0,5
1,0
Nd2-x
CexCuO
4+ x=0.15
optimally annealing T=4.2 K
RH (
10-1
0 m3 /C
)
H (kOe)
15
0 20 40 60 80 100
-20
-15
-10
-5
0
5
10
Nd2-x
CexCuO
4+ x=0.17
optimally annealing T=4.2 KR
H (
10-1
0 m3 /C
)
H (kOe)
0 10 20 30 40 50 60-15
-10
-5
0
5
10
15
Nd2-x
CexCuO
4+ x=0.18
optimally annealing T=4.2 K
RH (
10-1
0 m3 /C
)
H (kOe)
The theoretical model
We used the Bardeen-Stephen model, which has been adapted to respond to two types of
carriers (electrons and holes). Each of the carriers gives a contribution to the conductivity and Hall
coefficient: he 222
hhee RRR where Re, σe - is the contribution of electrons, and Rh, σh - the contribution of the holes.
Bardeen-Stephen model gives an expression for the resistivity and Hall coefficient for one type
of carrier in the form:
HHHHρρ
p
i
c
p
nixxi
2 HH
HHRR
p
i
c
p
nii
2
i=e, h.
where ρni = 1/eniμi are resistivities in the normal state, Rni = ± 1/eni are Hall coefficients in the
normal state, Hc2i are upper magnetic fields, Hp is depinning field, ni, μi are carrier concentrations
and mobilities, respectively (for electrons i=e and for holes i=h).
Thus, if H<Hp, the samples are in the SC state and Ri, ρi=0; if H>Hc2i, then the samples are in
the normal state and Ri=Rni, ρxxi=ρni.
16
In the calculations, the fields Hc2e, Hc2
h, Hp are found graphically from the dependence of R(H)
and ρxx(H), the mobilities are close in magnitude: μh/μe~1. As a result of the calculations parameters
ne, nh, μe, μh were obtained.
Dependences of RH(H) and ρxx(H) for
optimally annealing Nd1.85Ce0.15CuO4+δ
T=4.2К
0
1
2
3
4
5
6
7 Experimental data Theoretical data
b
a
xx (
10-7
*m
)
0 20 40 60 80 100
-2
-1
0
1
RH (
10-1
0 m3 /C
)
H (kOe) 17
Dependences of RH(H) and ρxx(H) for
optimally annealing Nd1.83Ce0.17CuO4+δ
T=4.2К
0
1
2
Experimental data Theoretical data
xx (
10-7
*m
)
0 20 40 60 80 100-3
-2
-1
0
RH (
10-1
0 m3 /C
)
H (kOe) 18
Dependences of RH(H) and ρxx(H) for optimally annealing
Nd1.82Ce0.18CuO4+δ
T=4.2К
0
1
2
3
4 Experimental data Theoretical data
xx (
10-7
*m
)
0 20 40 60 80-20
-10
0
10
RH (
10-1
0 m3 /C
)
H (kOe) 19
The main parameters of the samples Nd2-
xCexCuO4+δ
(optimally annealing)
x ne,cm-3 nh,cm-3 b=μh/μe
0.15 6.3∙1021 5.2∙1021 0.75
0.17 1.7∙1021 6.7∙1021 0.5
0.18 1.6∙1019 1.2∙1021 0.9
20
Dependences of RH(H) and ρxx(H) for
optimally annealing Nd1.85Ce0.15CuO4+δ
T=4.2К
0
1
2
3
4
5
6
7 Experimental data Theoretical data
b
a
xx (
10-7
*m
)
0 20 40 60 80 100
-2
-1
0
1
RH (
10-1
0 m3 /C
)
H (kOe) 21
Dependences of RH(H) and ρxx(H) for
non-optimally annealing
Nd1.85Ce0.15CuO4+δ
T=4.2К
0
5
10
15
20
25
30 Experimental data Theoretical data
b
a
xx (
10-7
*m
)
0 20 40 60 80 100
-5
-4
-3
-2
-1
0
RH (
10-1
0 m3 /C
)
H (kOe) 22
Dependences of RH(H) and ρxx(H) for
as grown Nd1.85Ce0.15CuO4+δ
T=4.2К
0
5
10
15
20
25
30
b
a
Experimental data Theoretical data
xx (
10-7
*m
)
0 20 40 60 80 100-75
-50
-25
0
RH (
10-1
0 m3 /C
)
H (kOe) 23
The main parameters of the samples Nd1.85Ce0.15CuO4+δ
Sample ne,cm-3 nh,cm-3b=μh/μe
Optimally annealing
6.3∙102
1
5.2∙102
1 0.75
Non-optimally annealing
1.1∙102
2
2.4∙102
1 0.95
As grown1.6∙102
0
1.7∙102
0 0.95
24
Conclusion
The model is based on a simple Drude model for
the normal state and semi-phenomenological
model for the Bardeen-Stephen mixed state
(modified considering the coexistence of
electrons and holes) can to qualitatively describe
the behavior of the Hall coefficient.
The possibility of such descriptions allows us to
consider the relationship of the hole and electron
subsystems as one of the important properties
inherent in cuprate HTSC.
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