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Resistivity and the solid-to-liquid transition in high-temperature superconductors
KTH, School of Information and Communication Technology (ICT), Material Physics.
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

In high-temperature superconductors a large region of the magnetic phase diagram is occupied by a vortex phase that displays a number of exciting phenomena. At low temperatures, vortices form a truly superconducting solid phase which at high temperatures turns into a dissipative vortex liquid. The character of the transition between these two phases depends on the amount and type of disorder present in the system. For weak point disorder the vortex solid-to-liquid transition is a first-order melting. In the presence of strong point disorder the solid is thought to be a vortex-glass and the transition into the liquid is instead of second order. When the disorder is correlated, like twin boundaries or artificially introduced columnar defects, the transition is also second order, but has essentially different properties. In this work, the transition between the solid and liquid phases of the vortex state has been studied by resistive transport measurements in mainly YBa2Cu3O7-[delta](YBCO) single crystals with different types of disorder.

The vortex-glass transition has been investigated in an extended model for the vortex-liquid resistivity close to the transition that takes into account both the temperature and magnetic field dependence of the transition line. The resistivity of samples with different properties was measured with various contact configurations at several magnetic fields and analyzed within this model. For each sample, attempts were made to scale the transition curves to one curve according to a suitable scaling variable predicted by the model. Good scaling was found in a number of different situations. The influence of increasing anisotropy and angular dependence of the magnetic field in the model were also considered.

The vortex solid-to-liquid transition was also studied in heavy-ion irradiated YBCO single crystals. The ions create columnar defects in the sample that act as correlated disorder. A magnetic field was applied at a tilt angle with respect to the direction of the columns. At the transition the resistance disappears as a power law with different exponents in the three orthogonal directions considered. This provides evidence for a new type of critical behavior with fully anisotropic critical scaling properties not previously found in any physical system.

The effect on the vortex solid-to-liquid transition of high magnetic fields applied parallel to the superconducting layers of underdoped YBCO single crystals was also studied. Some novel features were observed: a sharp kink appearing close to Tc at high magnetic fields and a triple dip in the angular dependence of the resistivity close to B||ab in some regions of the phase diagram.

Abstract [sv]

I högtemperatursupraledare består en stor del av det magnetiska fasdiagrammet av en vortexfas som uppvisar ett flertal spännande fenomen. Vid låga temperaturer bildar vortexarna en fast vortexfas utan elektriskt motstånd. Vid högre temperatur övergår denna fas till en dissipativ vortexvätska. Egenskaperna hos denna fasövergång beror på oordningen i form av defekter. Vid svag punktoordning är fasomvandlingen mellan det fasta och flytande vortextillståndet en första ordningens smältövergång. Vid stark punktoordning anses den fasta fasen vara ett vortexglas och övergången till vortexvätskan är istället av andra ordningen. När oordningen är korrelerad, som för tvillinggränser eller artificiellt skapade kolumndefekter, är övergången också av andra ordningen men med väsentligt annorlunda egenskaper. I detta arbete har övergången mellan det fasta och det flytande vortextillståndet studerats med resistiva transportmätningar i framförallt enkristaller av YBa2Cu3O7-[delta] (YBCO) med olika typer av oordning.

Vortexglasövergången har undersökts i en utvidgad modell för resistansen i vortexvätskan nära fasövergången där hänsyn tas till såväl temperatur- som fältberoendet. Resistansen hos prover med olika egenskaper mättes i varierande magnetfält och i flera kontaktkonfigurationer och analyserades inom denna modell. Övergångskurvorna skalades till en kurva med en skalningsvariabel som givits av modellen. God skalning uppnåddes i flera olika fall. Effekten av ökande anisotropi och vinkelberoendet i modellen undersöktes också.

Vortexövergången mellan det fasta och det flytande vortextillståndet undersöktes även i enkristaller av YBCO bestrålade med tunga joner. Jonerna skapade kolumndefekter som fungerar som korrelerad oordning. Vinkeln mellan pålagt magnetfält och dessa kolumndefekter varierades. Vid fasövergången avtar resistansen som en potenslag med olika exponenter i de tre undersökta ortogonala riktningarna. Detta ger experimentell belägg för en ny typ av kritiskt beteende med fullständigt anisotropa kritiska skalningsegenskaper.

Egenskaparna hos på vortexövergången mellan fast och flytande fas vid höga magnetfält parallella med de supraledande lagren hos underdopade YBCO enkristaller undersöktes också. Några nya effekter observerades: en skarp knyck uppstod nära Tc vid höga magnetfält och en tredubbel dipp i den vinkelberoende resistiviteten nära B||ab i några regioner av fasdiagrammet.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , xii, 84 p.
Series
Trita-ICT/MAP, 2007:2
Keyword [en]
high-temperature superconductors, vortex dynamics, vortex solid-to-liquid transition, critical scaling, glass transition, Bose glass, heavy-ion irradiation, YBCO, Tl2Ba2CaCu2O8+d, oxygen deficiency.
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-4251ISBN: 978-91-7178-545-9 (print)OAI: oai:DiVA.org:kth-4251DiVA: diva2:11466
Public defence
2007-01-19, F3, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20110125Available from: 2006-12-22 Created: 2006-12-22 Last updated: 2011-11-28Bibliographically approved
List of papers
1. Scaling of the vortex liquid c-axis resistivity in underdoped YBa2Cu3O7-[delta]
Open this publication in new window or tab >>Scaling of the vortex liquid c-axis resistivity in underdoped YBa2Cu3O7-[delta]
2004 (English)In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 408, 583-584 p.Article in journal (Refereed) Published
Abstract [en]

 The c-axis resistivity was measured in a twinned, underdoped YBa2Cu3O7-delta (YBCO) single crystal with T-c = 82.2 K. Resistive transition curves for fields Lip to 12 T applied along the c-axis were scaled to one function giving a good scaling. The scaling variable is the same as for the ab resistivity in optimally doped and underdoped YBCO single crystals [Phys. Rev. B 63 (2001) 184511]. This result provides further support to a coherent description of the vortex-liquid resistivity.

Keyword
YBa2Cu3O7-delta, vortex-liquid resistivity, scaling
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-6684 (URN)10.1016/j.physc.2004.03.037 (DOI)000224051700247 ()2-s2.0-4344692475 (Scopus ID)
Note
QC 20100929. 7th International Conference on Materials and Mechanisms of Superconductive and High Temperature Superconductors. Rio de Janeiro, BRAZIL. MAY 25-30, 2003 Available from: 2006-12-22 Created: 2006-12-22 Last updated: 2017-12-14Bibliographically approved
2. Scaling of vortex-liquid resistivity in high-Tc superconductors
Open this publication in new window or tab >>Scaling of vortex-liquid resistivity in high-Tc superconductors
2005 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 71, no 2, 024507- p.Article in journal (Refereed) Published
Abstract [en]

Analysis of the in-plane resistivity of a Tl2Ba2CaCu2O8+delta thin film and of several oxygen-deficient YBa2Cu3O7-delta single crystals in magnetic fields 0less than or equal toBless than or equal to12 T applied along the crystallographic c axis were performed to study the resistive transition into the glassy state. The transition curves were scaled according to a modified model for the vortex-liquid resistivity, finding good scaling only for fields below a certain value B-0, consistent with the field-induced crossover between a three-dimensional and quasi-two-dimensional regime of the vortex fluctuations reported in several works. This indicates that for low fields the vortex state is in fact three dimensional and provides further support to a coherent description of the vortex-liquid resisitivity.

Keyword
yba2cu3o7-delta thin-films, irreversibility line, crossover, phase, field, fluctuations, temperature, transition, disorder, lattice
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-6685 (URN)10.1103/PhysRevB.71.024507 (DOI)000226735400090 ()2-s2.0-16844382351 (Scopus ID)
Note
QC 20110125Available from: 2006-12-22 Created: 2006-12-22 Last updated: 2017-12-14Bibliographically approved
3. Scaling of the B-dependent resistivity for different orientations in Fe doped YBa2Cu3O7-[delta]
Open this publication in new window or tab >>Scaling of the B-dependent resistivity for different orientations in Fe doped YBa2Cu3O7-[delta]
2005 (English)In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 423, no 1-2, 69-73 p.Article in journal (Refereed) Published
Abstract [en]

The angular dependence of a previously proposed modified model of the vortex glass transition has been investigated. The in-plane resistivity in an optimally oxygen doped YBa2Cu3O7-delta single crystal, doped with 1% Fe, was measured in fields up to 12 T applied with different orientations with respect to the crystallographic c-axis. The transition curves at all orientations were successfully scaled into one curve according to a scaling variable for the normalized resistivity. Characteristic parameters of the model, like the glass transition temperature and the magnetic field B-0, were measured at each orientation and were in good agreement with the expected values. These results show that the model proposed is valid also for fields applied outside the c-axis, giving further support to a more consistent description of the vortex liquid resistivity.

Keyword
Scaling, Vortex liquid resistivity, YBa2Cu3O7-δ
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-6686 (URN)10.1016/j.physc.2005.03.023 (DOI)000229806100011 ()2-s2.0-19144364341 (Scopus ID)
Note
QC 20100929Available from: 2006-12-22 Created: 2006-12-22 Last updated: 2017-12-14Bibliographically approved
4. Fully anisotropic superconducting transition in ion-irradiated YBa2Cu3O7-delta with a tilted magnetic field
Open this publication in new window or tab >>Fully anisotropic superconducting transition in ion-irradiated YBa2Cu3O7-delta with a tilted magnetic field
Show others...
2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 10, 100504- p.Article in journal (Refereed) Published
Abstract [en]

We consider the superconducting vortex solid-to-liquid transition in heavy ion-irradiated untwinned YBa2Cu3O7-delta single crystals in the case where the magnetic field direction does not coincide with that of the irradiation-induced linear columnar defects. For a certain range of angles, the resistivities measured in three orthogonal spatial directions vanish at the transition as three clearly different powers of reduced temperature. At previously known second-order phase transitions, scaling of physical quantities has either been isotropic or anisotropic in one direction. Thus, our findings yield evidence for a new type of critical behavior with fully anisotropic critical exponents.

Keyword
high-temperature superconductors, bose-glass-transition, correlated disorder, columnar defects, single-crystals, localization, vortices, phase
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-16498 (URN)10.1103/PhysRevB.75.100504 (DOI)000245329100009 ()2-s2.0-33947515033 (Scopus ID)
Note
QC 20100811Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved

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