Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userEnhancement of the superconducting critical temperature of Sr2CuO3+d up to 95K by ordering dopant atoms
49
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We address the question of whether the superconducting transition temperature (Tc) of high-Tc cuprates is enhanced when randomly distributed dopant atoms form an ordered array in the charge reservoir layers. This study is possible for the Sr2CuO3+d superconductor with K2NiF4-type structure in which oxygen atoms only partially occupy the apical sites next to the CuO2 planes and act as hole-dopants. We show that remarkable Tc enhancement up to 95K in this mono CuO2 layered HTS is associated with the apical oxygen ordering, not to the hole concentration change. The result points a route toward further enhancement of Tc in cuprate superconductors.
rate research
Read More
We report large enhancement of upper critical field Hc2 observed in superconducting Sr2RuO4 thin films. Through dimensional crossover approaching two dimensions, Hc2 except the in-plane field direction is dramatically enhanced compared to bulks, following a definite relation distinct from bulk one between Hc2 and the transition temperature. The anomalous enhancement of Hc2 is highly suggestive of important changes of the superconducting properties, possibly accompanied with rotation of the triplet d-vector. Our findings will become a crucial step to further explore exotic properties by employing Sr2RuO4 thin films.
A relatively high critical temperature, Tc, approaching 40 K, places the recently-discovered superconductor magnesium diboride (MgB2) intermediate between the families of low- and copper-oxide-based high-temperature superconductors (HTS). Supercurrent flow in MgB2 is unhindered by grain boundaries, unlike the HTS materials. Thus, long polycrystalline MgB2 conductors may be easier to fabricate, and so could fill a potentially important niche of applications in the 20 to 30 K temperature range. However, one disadvantage of MgB2 is that in bulk material the critical current density, Jc, appears to drop more rapidly with increasing magnetic field than it does in the HTS phases. The magnitude and field dependence of Jc are related to the presence of structural defects that can pin the quantised magnetic vortices that permeate the material, and prevent them from moving under the action of the Lorentz force. Vortex studies suggest that it is the paucity of suitable defects in MgB2 that causes the rapid decay of Jc with field. Here we show that modest levels of atomic disorder, induced by proton irradiation, enhance the pinning, and so increase Jc significantly at high fields. We anticipate that chemical doping or mechanical processing should be capable of generating similar levels of disorder, and so achieve technologically-attractive performance in MgB2 by economically-viable routes.
Many of the electronic properties of high-temperature cuprate superconductors (HTSC) are strongly dependent on the number of charge carriers put into the CuO$_2$ planes (doping). Superconductivity appears over a dome-shaped region of the doping-temperature phase diagram. The highest critical temperature (Tc) is obtained for the so-called optimum doping. The doping mechanism is usually chemical; it can be done by cationic substitution. This is the case, for example, in La$_{2-x}$Sr$_x$CuO$_4$ where La3+ is replaced by Sr2+ thus adding a hole to the CuO$_2$ planes. A similar effect is achieved by adding oxygen as in the case of YBa$_2$Cu$_3$O$_{6+delta}$ where $delta$ represents the excess oxygen in the sample. In this paper we report on a different mechanism, one that enables the addition or removal of carriers from the surface of the HTSC. This method utilizes a self-assembled monolayer (SAM) of polar molecules adsorbed on the cuprate surface. In the case of optically active molecules, the polarity of the SAM can be modulated by shining light on the coated surface. This results in a light-induced modulation of the superconducting phase transition of the sample. The ability to control the superconducting transition temperature with the use of SAMs makes these surfaces practical for various devices such as switches and detectors based on high-Tc superconductors.
Super-high resolution laser-based angle-resolved photoemission measurements have been carried out on Bi2Sr2CaCu2O8+d (Bi2212) superconductors to investigate momentum dependence of electron coupling with collective excitations (modes). Two coexisting energy scales are clearly revealed over a large momentum space for the first time in the superconducting state of an overdoped Bi2212 superconductor. These two energy scales exhibit distinct momentum dependence: one keeps its energy near 78 meV over a large momentum space while the other changes its energy from $sim$40 meV near the antinodal region to $sim$70 meV near the nodal region. These observations provide a new picture on momentum evolution of electron-boson coupling in Bi2212 that electrons are coupled with two sharp modes simultaneously over a large momentum space in the superconducting states. Their unusual momentum dependence poses a challenge to our current understanding of electron-mode-coupling and its role for high temperature superconductivity in cuprate superconductors.
We report successful growth of flux free large single crystals of superconducting FeSe1/2Te1/2 with typical dimensions of up to few cm. The AC and DC magnetic measurements revealed the superconducting transition temperature (Tc) value of around 11.5K and the iso-thermal MH showed typical type-II superconducting behavior. The lower critical field being estimated by measuring the low field iso-thermal magnetization in superconducting regime is found to be above 200 Oe at 0K.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
