Figure 3a shows the zero bias conductance spectra mapping of a surface region shown in fig. Soon after its discovery in 1911 by dutch physicist heike kamerlingh onnes and his collaborators, cornelis dorsman, gerrit jan flim and gilles holst, superconductivity inspired dreams of noloss electrical transmission. The resistivity, carrier concentration and mobility of the nb. Electrical conductivity of epitaxial srtio3 thin films as a. The record superconducting transition temperature tc for the ironbased hightemperature superconductors fehts has long been 56 k. Enhanced thermoelectric properties of lightly nb doped. Pdf tunable critical temperature for superconductivity. A microscopic theory of superconductivity was developed in 1957 by john bardeen, leon cooper and j.
Hopkins1,a 1department of mechanical and aerospace engineering, university of virginia, charlottesville, virginia 22904, usa 2sandia national laboratories, albuquerque, new mexico 87185, usa. Infrared spectroscopy of an epitaxial batio 3srtio 3 superlattice grown on a 110 smsco 3 substrate v. Thermal conductivity of nanograined srtio 3 thin films brian m. High mobility 2dimensional electron gas at laalo3 srtio3 interface prepared by spin coating chemical methods tahira khan1,2, hui zhang1,2, hongrui zhang1,2, xi yan1,2, deshun hong1,2,furonghan1,2, yuansha chen1,2, baogen shen1,2 and jirong sun1,2 1beijing national laboratory for condensed matter and institute of physics, chinese academy of sciences, beijing 100190, peoples republic of china.
Nov 12, 20 we report the electrical topgating of a 2dimensional electron gas 2deg formed at the laalo3 srtio3 interface, using electronbeam evaporated au gate electrodes. In the superconductive state the current carrying species is the electron pair. The fuel cellinduced phase transition was observed from the insulating lst to a super o2 conductivity of 0. Pdf evidence of weak superconductivity at the room. Low thermal conductivity of redoped sro srtio3 1 ruddlesden popper phase bulk materials prepared by molten salt method article pdf available in electronic materials letters 145 april 2018. Phonon mechanism in the most dilute superconductor ntype srtio3. High mobility 2dimensional electron gas at laalo3srtio3. Modulation of conductance and superconductivity by top. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero, a superconductor has a.
Anisotropic properties of a single superconducting cacuo2. Tuller, and bilge yildiz plastic strain engineering was applied to induce controllable changes in electronic and oxygen ion conductivity in oxides by orders of magnitude, without. Jespersen,2 yunzhong chen,1 nini pryds1 1 department of energy conversion and storage, technical university of denmark, dtu riso campus, 4000. The structured topgates enable a local tuning and complete onoff switching of the interface super conductivity, while maintaining the usual, intrinsic. The interface between the oxide insulators laalo3 and srtio3 laosto hosts a twodimensional electron gas. In 1986, it was discovered that some cuprateperovskite ceramic materials have a critical temperature above 90 k. Any material exhibiting these properties is a superconductor. Strontium titanate srtio3 properties and applications.
Sto thin films with good crystallinity and smooth surfaces were epitaxially grown on srtio 3 sto 1 0 0 substrates by laser molecular beam epitaxy. The combination of interfacial conductivity and superconductivity at ultralow temperatures with the physical phenomena of the oxide parent materials has fueled extensive research in the field since its discovery in 2004. Schlom1,6 1department of materials science and engineering, cornell university, ithaca, new york 148531501, usa 2department of materials science and. The nature of superconductivity in srtio3, the first oxide superconductor to be discovered. Tuning thermal conductivity in homoepitaxial srtio 3 films via defects charles m. Phonon mechanism in the most dilute superconductor ntype srtio3 lev p. It is used in varistors and tunable hts microwave filters. Theoretical study of lattice thermal conduction in srtio3. Enhanced thermoelectric properties of lightly nb doped srtio3 thin. We report a high lateral ionic conductivity, showing up to eight orders of magnitude enhancement near room temperature, in yttriastabilized zirconia yszstrontium titanate epitaxial heterostructures. Scanning superconducting quantum interference device squid. We report on the superconductivity of lanthanumdoped srtio3 thin films grown by offaxis laser ablation on laalo3, srtio3, and ndgao3 substrates in. We report the occurrence of high tc superconductivity in the bilayer cacuo2 srtio3, where both the constituent oxides are insulating.
Control of electrical conductivity in laser deposited srtio3. One important example is the appearance of superconductivity at the interface between insulating oxides, although, until now, with very low tc. Singlegap superconductivity and dome of superfluid density in nb. Polaronic behavior in a weakcoupling superconductor. Interfaceinduced superconductivity and straindependent. Interplay of point defects, biaxial strain, and thermal conductivity in homoepitaxial srtio3 thin films appl. Monolayer fese on srtio 3 dennis huang1 and jennifer e. Pdf twodimensional superconductivity at 110 laalo3srtio3. Defects, stoichiometry, and electronic transport in srtio3. Printed in great britain superconductivity and structural instability in srtio3 philip b. Tuning thermal conductivity in homoepitaxial srtio3 films.
Colossal ionic conductivity at interfaces of epitaxial. Pdf electrical and structural properties of nbdoped. Ferroelectric enhancement of superconductivity in compressively. High insulation resistivity and ultralow dielectric loss in. The structure around zero voltage is due to the superconductivity of indium and starts to develop at 3. This temperature, called the transition temperature, varies for different materials but generally is below 20 k. Electrical and structural properties of nbdoped srtio 3. The interface between lanthanum aluminate laalo 3 and strontium titanate srtio 3 is a notable materials interface because it exhibits properties not found in its constituent materials. Conductivity readings are converted to tds readings by multiplication with a known mathematical factor. Superconductivity, complete disappearance of electrical resistance in various solids when they are cooled below a characteristic temperature. Feb 05, 2004 strontium titanate srtio3 has a perovskite structure and is probably best known for its high dielectric constant. Although srtio3 was the first oxide superconductor to be discovered 1, the nature of its. Electron coupling to polar modes with energies above the fermi level singlesout doped srtio3 among all other superconductors. Pdf novel low dimensional quantum phenomena are expected at 110 laalo3srtio3 laosto interfaces after the quasi two dimensional.
The underlying mechanism of superconductivity differs from the usual one in that relatively few electrons interact mainly via an unscreened polar mode whose energy lies above the fermi level. Bos a a institute of chemical sciences and centre for advanced energy storage and recovery, school of engineering and physical sciences, heriotwatt university, edinburgh, eh14 4as, united. Superconductivity and structural instability in srtio3. Besides the interfaceengineered hightemperature superconductivity, other exotic physics may occur in 1uc fese under different conditions, including electron correla. Infrared spectroscopy of an epitaxial batio3srtio3. Srtio3 is also an incipient ferroelectric, and several recent theoretical studies have suggested that the two properties may be linked.
As the tempera ture is lowered, small dips appear at about 0. Superconductivity is the set of physical properties observed in certain materials, wherein electrical resistance vanishes and from which magnetic flux fields are expelled. In the present paper we use a combination of scanning transmission electron microscopy and. These anomalies have previously been associated with an enhancement of the superconducting critical temperature in doped srtio3 films. What is superconductivity history of superconductivity meissner effect exit applications. Srtio 3 100 epitaxial films with thicknesses of 3, 1. Highly conductive nb doped srtio3 epitaxial thin films.
For the cooper pair to scatter it would have to change its state like an electron in normal metal. Pdf tuning thermal conductivity in homoepitaxial srtio3. Seeing oxygen disorder in yszsrtio3 colossal ionic. The role of srtio 3 phonon penetrating into thin fese films in the enhancement of superconductivity shuyuan zhang, 1jiaqi guan, xun jia, 1bing liu, weihua wang, fangsen li,2 lili wang,2,3, xucun ma, 2,3qikun xue, jiandi zhang, 4e. Lattice thermal conductivity of srtio3tio2 superlattice. We will look at features of superconductors before the discovery of the bcs theory, and examine the assumptions and methods used to develop the theory. Xi3 1institute of physics, ascr, na slovance 2, 182 21 prague 8, czech republic. In the meantime, the powerful advantages that superconductors offer suggest a wide array of present and future applications in the areas of electric power, transportation, medical imaging and diagnostics, nuclear magnetic resonance nmr, industrial processing, high energy physics, wireless communications, instrumentation, sensors, radar, highend computing and even cryogenics source. At low temperatures it approaches a ferroelectric phase transition with a very large dielectric constant 10 4 but remains paraelectric down to the lowest temperatures measured as a result of quantum.
The nature of superconductivity in srtio3, the first oxide superconductor to be discovered, remains a subject of intense debate several decades after its discovery. The phase structure and micromorphology of the ceramic samples were studied by the analysis of xrd and sem, respectively. Superconductivity news physics news, quantum physics. Pdf modulation of conductance and superconductivity by. Lanthanum aluminatestrontium titanate interface wikipedia.
Pdf electrical conductivity and structural stability of. Interfaceinduced hightemperature superconductivity in. Individually, laalo 3 and srtio 3 are nonmagnetic insulators, yet laalo 3 srtio 3 interfaces can exhibit electrical metallic conductivity, superconductivity, ferromagnetism, large negative inplane. Tunable oxygen diffusion and electronic conduction in srtio 3 by dislocationinduced space charge fields kiran k.
In these structures, epitaxial laalo3 films grown by pulsed laser deposition induce the 2degs at the interface to the srtio3 substrate and simultaneously act as the gate dielectric. Modulation of conductance and superconductivity by topgating. Pdf thermal conductivity of nanograined srtio3 thin films. Polaronic behavior in a weakcoupling superconductor adrian g. Plummer, xuetao zhu,1, yand jiandong guo1,3, z 1beijing national laboratory for condensed matter physics and institute of physics. Hoffman1,2 1department of physics, harvard university, cambridge, massachusetts 028. Colossal ionic conductivity at interfaces of epitaxial zro2.
Mechanism of superconductivity in srtio3 sciencedirect. We report the electrical topgating of a 2dimensional electron gas 2deg formed at the laalo3 srtio3 interface, using electronbeam evaporated au gate electrodes. Srtio 3 for research and development growth method. High tc superconductivity at the interface between. Strontium titanates mixed conductivity has attracted attention for use in solid oxide fuel cells sofcs. Strontium titanate is an oxide of strontium and titanium with the chemical formula sr ti o 3. In most materials, with so few electrons it becomes dif. It demonstrates both electronic and ionic conductivity which is useful for sofc electrodes because there is an exchange of gas and oxygen ions in the material and electrons on both sides of the cell. The occurrence of the meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics. Chapter 2 strontium titanate 14 the bo 6 octahedra will tilt in order to fill space and the symmetry of the crystal structure is lowered. Superconductivity in the vicinity of a ferroelectric quantum. Here, two dimensional superconductivity of 110 laosto samples with a superconducting transition temperature of. High tc superconductivity at the interface between the. Pdf electrical and structural properties of nbdoped srtio3.
At room temperature, it is a centrosymmetric paraelectric material with a perovskite structure. An international team of researchers has discovered the hydrogen atoms in a metal hydride material are much more tightly spaced than had been predicted for decadesa feature that could possibly. Pdf morphologycontrolled synthesis of srtio3 nanocube. The factor depends on the reference material used to prepare the standard. Moreover, the sto block cannot play the role of a separating layer as it does in sls, and therefore no dependence of the super. Colossal ionic conductivity was recently discovered in ysz srtio3 multilayers and was explained in terms of strain and interfaceenhanced disorder of the o sublattice. Recently, in singlelayer fese films grown on srtio3. We argue that superconductivity of ndoped srtio3 results from the interaction of electrons with several longitudinal lo optical phonons with. Bednorz for growing the singlecrystal samples and to t. Pdf we measure the thermal conductivities of nanograined strontium titanate ng srtio3 films deposited on sapphire substrates via timedomain. Phonon mechanism in the most dilute superconductor ntype. Pdf low thermal conductivity of redoped srosrtio31. High tc superconductivity at the interface between the cacuo2. Such high ionic conductivity is due to the incorporation of fe, thermal, and an intrinsic property of ptype semiconductor electrolyte.
The electrical conductivities of the thin films were systematically investigated as a function of temperature and ambient oxygen partial pressure. Strontium titanate srtio3 has a perovskite structure and is probably best known for its high dielectric constant. Energy gap of the superconducting semiconductor srtio3. Electrical conductivity and structural stability of ladoped srtio3 with asite deficiency as anode materials for solid oxide fuel cells. To investigate whether such a connection exists, we grew strained, epitaxial srtio3 films.
Enhancing superconductivity in srtio3 films with strain. We will then calculate and study interesting quantities of the su. Magnetism and conductivity along structural domain walls. The perovskite oxide srtio3 is an ntype semiconductor, which exhibits superconductivity at low temperatures even though there are extraordinarily few electrons. Thermal conductivity of nanograined srtio3 thin films. Twodimensional superconductivity at 110 laalo3srtio3. Influence of niobium content on the lattice parameters and electrical conductivity has been reported.
I argue that the claimed ionic conductivity lacks experimental support and that the observed conductivity enhancement is most probably due to the ptype. Pdf modulation of conductance and superconductivity by top. Enhancing superconductivity in srtio3 films with strain science. The electronic conductivity of nbdoped srtio3 single crystals, srti1. Burstein mattheiss has recently calculated the effects of the 105 structural phase transition on the conduction band and. Robert schrieffer, which is known as the bcs theory. Kammerlingh onnes in 1911 was followed by the observation of other metals which exhibit zero resistivity below a certain critical temperature. Srtio3 exhibits a superconducting dome upon doping with nb, with a maximum. The results obtained for the cacuo 2srtio 3 interface can be extended to multilayered high t c cuprates, contributing to explain the dependence of t c on the number of cuo. The central feature of the bcs theory is that two electrons in the superconductor are able to form a bound pair called a cooper pair if they somehow experience an attractive interaction between.
Tunable oxygen diffusion and electronic conduction in. Enhanced thermoelectric properties of lightly nb doped srtio3. Gorkova,1 anational high magnetic field laboratory, florida state university, tallahassee, fl 32310 contributed by lev p. Glasslike thermal conductivity in srtio thermoelectrics. On the other hand, if t is larger than 1 due to a large a or small b ion then tetragonal and hexagonal variants of the perovskite structure are stable, e. May 20, 2009 niobiumdoped strontium titanate synthesized via conventional solidstate reaction has been studied.
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