Observation of Vortex Lattice Related Anomalies in Polycrystalline YBa2Cu3O7-x Near the Superconducting Transition

doi:10.4236/jmp.2012.310183

Paper Menu >>

Journal Menu >>

Journal of Modern Physics, 2012, 3, 1487-1489

http://dx.doi.org/10.4236/jmp.2012.310183 Published Online October 2012 (http://www.SciRP.org/journal/jmp)

Observation of Vortex Lattice Related Anomalies in

Polycrystalline YBa2Cu3O7−x near the

Superconducting Transition

S. B. Ota

Institute of Physics, Bhubaneswar, India

Email: [email protected]

Received July 30, 2012; revised August 28, 2012; accepted September 7, 2012

ABSTRACT

The d.c. I-V characteristic of polycrystalline YBa2Cu 3O7−x high temperature superconductors (HTSC) is measured near

the transition temperature (Tc). The Tc was found to be 90 K with a width of 2 K. The voltage was measured at various

current values and with reversing the current. A difference in voltage was found for forward and reverse current direc-

tions near Tc. The observed directionality of the I-V characteristic can be understood in terms of quantized magnetic

flux by the self-field of the current and the proximity junctions in these materials. This can also be understood qualita-

tively as due to the d-wave superconductivity. The measured dc voltage showed increased noise near Tc which is possi-

bly related to 1/f noise due to the motion of Abrikosov flux lines.

Keywords: HTSC; Transition Temperature; 1/f Noise

1. Introduction

Superconducting materials have attracted interest in re-

cent years [1-17]. Such materials show negligible elec-

trical resistance and magnetic flux exclusion. Electrical

and thermal properties of these materials have been stud-

ied below 100 K. These materials have technological

applications which involve operation across or below the

superconducting transition. Superconducting magnets,

superconducting switches, temperature standards and

switching devices are some examples. The transition

temperature of YBa2Cu3O7 which is a high temperature

superconductor is about 90 K [8,9,12-16]. The effect of

magnetic field on the specific heat anomaly near the su-

perconducting transition is considerably different from

the effect on conventional superconductors. It has been

found that the specific heat peak associated with the su-

perconducting transition mainly reduces in amplitude and

broadens by the application of magnetic field. This is

unlike the type-II conventional superconductors in which

case the application of magnetic field shifts the specific

heat jump at Tc to lower temperatures with practically

very little change in the shape of the anomaly. There are

also several other unusual behavior in the HTSC which is

not yet understood [18]. Other studies to understand the

microscopic filed distribution concerning the supercon-

ducting state has been carried out with high-field μSR

[19]. Here we note that other materials such as CuO has

also been studied in the context of theoretical under-

standing of HTSC [20,21].

2. Experiment

Electrical resistance measurement on polycrystalline

YBa2Cu3O7 was carried by an automated d.c. four termi-

nal technique [16]. This setup is built around a closed

cycle refrigerator. The YBa2Cu3O7 sample was in the

form of rectangular bar having dimension ≈ 1 × 2 × 11

mm3. The sample was characterized as as been discussed

elsewhere [8,9]. The electrical contacts made using silver

paste had a resistance of 30 Ohms for the two current

leads. The electrical resistance of the sample at 100 K

was nearly 0.1 Ohms. The current was varied from 1 mA

to 100 mA in steps using a Keithley model 224/2243

programmable current source. The dc voltage was meas-

ured using a Keithley model 182 sensitive digital volt-

meter. A calibrated type D silicon diode thermometer

was used in conjunction with a Leybold model LTC60

temperature controller to control and monitor the tem-

perature of the sample site. The calibrated diode has a

standard measurement accuracy of about 1 percent. The

measurement was done as the sample was warmed from

about 70 K. The HTSC has a superconducting transition

(Tc) of 90 K and a width of about 2 K. At each tempera-

ture the current was increased from 1 mA to 100 mA in

steps. For each current value, first the positive polarity of

S. B. OTA

1488

current was given and the voltage was measured. Then

the current was made negative with the same value and

the voltage was measured again. A systematic difference

in voltage (dV) was found in the measurement.

3. Conclusion

Figure 1 shows dV as a function of temperature for

YBa2Cu3O7. It is seen that the difference in voltage or the

directionality is enhanced near Tc. The directionality also

increases as the current is increased from 1 mA to 100

mA. The observed directionality should be present in

conventional superconducting materials but is enhanced

in case of YBa2Cu3O7. The theoretical understanding of

the observed directionality is as follows. The total current

through the superconductor can be written as follows:

 

diss disp

J J

con st

JJ (1)

where Js is the superconducting current, Jdisp is the dis-

placement current and Jdiss is the dissipation current. Jdisp

and Jdiss becomes negligible with time and therefore only

Js need to be considered for the equilibrium I-V charac-

teristic. Moreover, it is known that:

(2)

This gives rise to flux quantization and near the transi-

tion trapped quantized magnetic flux. This can give rise

to observed directionality. Such directionality can arise

possibly due to unconventional pairing [22]. The most

discussed unconventional pairing is in the context of high

temperature superconductors in which the pairing chan-

nel is l = 2 or d-wave. Such pairing states occur in various

Figure 1. The temperature dependence of difference in vol-

tage (dV) for YBa2Cu3O7. The transition temperature Tc is

nearly 90 K. dV is shown for two current values; 1 mA (■)

and 100 mA (◊).

theories based on microscopic models which can show

such unusual properties in the superconducting state.

The measured dc voltage also showed increased noise

near Tc. This can possibly arise due to the motion of Ab-

rikosov flux lines and has the nature similar to 1/f noise

[23,24].

The HTSC YBa2Cu3O7 has been studied by d.c. four

probe electrical resistance measurement near the super-

conducting transition. A directionality in the d.c. I-V

characteristic was observed. The observed directionality

can be understood theoretically as due to trapped quan-

tized magnetic flux. Theoretical understanding of such

observation is also consistent with microscopic models

based on d-wave superconducting state.

4. Acknowledgements

The author is benefited from his visit to Europe in 1988-

1992 for HTSC research, Xiamen, China during 1995 for

statistical physics conference and New Orleans and Dal-

las, USA during 2008 and 2011 respectively for APS

March meeting. The author acknowledges Dr. C. Ian-

nicello and others of American Institute of Physics for

providing access to the URL of AIP UniPHY.

REFERENCES

[1] S. B. Ota and V. C. Sahni, “Study of Tetragonality Pa-

rameter of Martensitic Transition in A15 Compounds,”

Journal of Physics C: Solid State Physics, Vol. 18, No. 35,

1985, pp. 6471-6479.

[2] S. B. Ota, “Martensitic Transition and Superconductivity

in A15 Compounds,” Physica B+C, Vol. 141, No. 2,

1986, pp. 159-170.

[3] S. B. Ota, “Superconductivity in A15 Compounds under

Non-Hydrostatic Stress,” Physical Review B, Vol. 35, No.

16, 1987, pp. 8730-8732. doi:10.1103/PhysRevB.35.8730

[4] L. R. Testardi, “Structural instability and superconductiv-

ity in A15 compounds,” Reviews of Modern Physics, Vol.

47, No. 3, 1975, pp. 637-648.

[5] M. Kataoka and N. Toyota, “Martensitic and Supercon-

ducting Phase Transitions in A15 Compounds,” Phase

Transitions, Vol. 8, No. 2, 1987, pp. 157-186.

doi:10.1080/01411598708209374

[6] J. W. Lynn, “High Temperature Superconductivity,”

Springer-Verlag, World Publishing Corporation, Beijing,

1991.

[7] E. Gmelin, “Studies of High Temperature Superconduc-

tors,” Nova Science, New York, 1996.

[8] S. B. Ota, T. V. C. S. Rao and V. C. Sahni, “Simple

Gadget for Variable Temperature Electrical Resistance

Measurement,” Cryogenics, Vol. 29, No. 7, 1989, pp.

760-761. doi:10.1016/0011-2275(89)90146-X

[9] S. B. Ota, et al., “The Maximum Sintering Temperature

and Electrical Characteristics of the High-Tc,” Journal of

Physics D: Applied Physics, Vol. 21, No. 8, 1988, pp.

S. B. OTA

1489

1308-1311. doi:10.1088/0022-3727/21/8/013

[10] S. B. Ota, et al., “Signature of Possible Vortex Lattice

Melting in Magnetic Hysteresis of High Tc

Bi2Sr2CaCu2O8+x,” Physica C, Vol. 157, No. 8, 1989, pp.

520-524. doi:10.1016/0921-4534(89)90280-3

[11] R. A. Rose, et al., “Scaling of the Vortex Pinning Force

in Bi2Sr2CaCu2O8+y,” Physica C, Vol. 170, No. 1-2, 1990,

pp. 51-55. doi:10.1016/0921-4534(90)90227-6

[12] S. B. Ota, G. P. Rapson and P. A. J. de Groot, “Irreversi-

bility Temperature and Meissner Fraction in High Tem-

perature Superconductors,” Physica B, Vol. 165-166,

1990, p. 1145.

[13] S. B. Ota, “Specific Heat in the Mixed State of Super-

conducting YBa2Cu3O7−x,” Physical Review B, Vol. 43,

No. 1, 1991, pp. 1237-1240.

doi:10.1103/PhysRevB.43.1237

[14] S. B. Ota, et al., “Anisotropic Magnetic Field Depend-

ence of the Specific Heat in Single Crystal Like

YBa2Cu3O7−x,” Physical Review B, Vol. 43, No.7, 1991,

pp. 6147-6150. doi:10.1103/PhysRevB.43.6147

[15] S. B. Ota, K. K. Nanda and S. N. Behera, “Ginzburg-

Landau Theory of Specific Heat Anomaly of High Tc

Superconductors in Magnetic Field,” Physica B, Vol.

194-196, 1994, pp. 1387-1388.

doi:10.1016/0921-4526(94)91193-2

[16] S. B. Ota, M. Bose, B. Sahoo and T. V. C. S. Rao, “Cur-

rent Dependence of Superconducting Transition in Sin-

tered Polycrystalline YBa2Cu3O7−x,” Physica C, Vol. 282-

287, 1997, p. 799.

[17] P. A. J. de Groot, et al., “Growth and Magnetic Charac-

terisation of Bi2Sr2CaCu2Oy Crystals,” Journal of Physics:

Condensed Matter, Vol. 1, No. 33, 1989, p. 5817.

doi:10.1088/0953-8984/1/33/028

[18] M. Oussena, P. A. J. de Groot, R. Gagnon and L. Taillefer,

“Lock-In Oscillations in Magnetic Hysteresis Curves of

Yba2Cu3O7−x Single Crystals,” Physical Review Letters,

Vol. 72, No. 22, 1994, pp. 3606-3609.

doi:10.1103/PhysRevLett.72.3606

[19] J. E. Sonier, “High Field μSR Studies of Superconducting

and Magnetic Correlation in Cuprates above Tc,” Journal

of Physics: Condensed Matter, Vol. 22, No. 20, 2010, Ar-

ticle ID: 203202. doi:10.1088/0953-8984/22/20/203202

[20] S. B. Ota and E. Gmelin, “Improved Analysis of Isoperi-

bol Heat Pulse Calorimetry,” Measurement Science and

Technology, Vol. 3, No. 11, 1992, pp. 1047-1049.

doi:10.1088/0957-0233/3/11/004

[21] S. B. Ota, “Origin of Incommensurate Structure in Sol-

ids,” Indian Journal of Pure and Applied Physics, Vol. 32,

1994, pp. 568-574.

[22] M. Sigrist and T. M. Rice, “Unusual Paramagnetic Phe-

nomena in Granular High Temperature Superconduc-

tors—A Consequence of d-Wave Pairing,” Reviews of

Modern Physics, Vol. 67, No. 2, 1995, pp. 503-513.

doi:10.1103/RevModPhys.67.503

[23] P. W. Anderson and Y. B. Kim, “Hard Superconductivity:

Theory of the Motion of Abrikosov Flux Lines,” Reviews

of Modern Physics, Vol. 36, No. 1, 1964, pp. 39-43.

doi:10.1103/RevModPhys.36.39

[24] Y. Yeshurun, A. P. Malozemoff and A. Shaulov, “Mag-

netic Relaxation in High Temperature Superconductors,”

Reviews of Modern Physics, Vol. 68, No. 3, 1996, pp.

911-950.