Galvanomagnetic effects in electron- doped superconducting compounds D. S. Petukhov 1, T. B. Charikova 1, G. I. Harus 1, N. G. Shelushinina 1, V. N. Neverov.

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.

25