arXiv subjects

Ajay D. Thakur

Publications and source records attributed to Ajay D. Thakur.

23 records · Page 2Linked to original sources

arXiv2010

Enhanced superconducting properties in FeCr$_x$Se

We report an enhancement of superconducting transition temperature ($T_{\rm c}$) when Chromium (Cr) is substituted in excess at the Iron (Fe) site (FeCr$_x$Se, $x=$0.01, 0.02 and 0.03). There is a corresponding increase in the superconducting volume fraction with $T_{\rm c}$ attaining a value of 11.2 K on 2 $%$ Cr substitution when compared to a $T_{\rm c}$ of 8.5 K for the conventional tetragonal Fe-excess sample Fe$_{1+x}$Se. The results point to the role of chemical pressure (introduced via ionic size variation at the Fe site upon Cr substitution in excess) on superconducting properties.

cond-mat.supr-con↗

arXiv2010

Disappearance of zinc impurity resonance in large gap region on Bi$_{\mathrm{2}}$Sr$_{\mathrm{2}}$CaCu$_{\mathrm{2}}$O$_{\mathrm{8+}δ}$ probed by scanning tunneling spectroscopy

Using Scanning tunneling spectroscopy (STS), we report the correlation between spatial gap inhomogeneity and the zinc (Zn) impurity resonance in single crystals of Bi$_{\mathrm{2}}$Sr$_{\mathrm{2}}$Ca(Cu$_{\mathrm{1-}x}$Zn$_{x}$)$_{\mathrm{2}}$O$_{\mathrm{8+}δ}$ with different carrier (hole) concentrations ($p$) at a fixed Zn concentration ($x$ $\sim$ 0.5 % per Cu atom). In all the samples, the impurity resonance lies only in the region where the gap value is less than $\sim$ 60 meV. Also the number of Zn resonance sites drastically decreases with decreasing $p$, in spite of the fixed $x$. These experimental results lead us to a conclusion that the Zn impurity resonance does not appear in the large gap region although the Zn impurity evidently resides in this region.

cond-mat.supr-con↗

arXiv2010

Observation of Vortex Matching Phenomena in Antidot Array of NbN Thin Film

We report vortex matching phenomenon in rectangular antidot array fabricated on epitaxial NbN thin film. The antidot array was fabricated using Focussed Ion Beam milling technique. The magneto-transport measurements points to a period doubling transition at higher magnetic field for rectangular lattices. The results are discussed within the light of several models including the multi-vortex model, the matched lattice model and the super-matched lattice model.

cond-mat.supr-con↗

arXiv2010

History and metastability effects in the intermediate state of mesoscopic type I superconducting Indium

We report detailed magnetic measurements on history and metastability effects in the intermediate state of mesoscopic cylinders of type I superconducting Indium. This includes the observation of topological hysteresis with the signature occurrence of different critical fields during flux entry and flux exit. We show the existence of a plethora of metastable configuration and recipes to access them. We also demonstrate the manifestation of superheating and supercooling of superconducting and normal states, respectively across the superconductivity transition.

cond-mat.supr-con↗

arXiv2009

Vortex matching effect in engineered thin films of NbN

We report robust vortex matching effects in antidot arrays fabricated on thin films of NbN. The near absence of hysteresis between field sweep directions indicates a negligible residual pinning in the host thin film. Owing to the very small coherence length of NbN thin films ($ξ< 5 nm$), the observations suggests the possibility of probing physics of vortices at true nanometer length scales in suitably fabricated structures.

cond-mat.supr-con↗