Om Prakash
@vttresearch.com
Research Scientist, Quantum computing hardware, VTT Technical Research Centre of Finland Ltd
VTT Technical Research Centre of Finland Ltd
RESEARCH INTERESTS
Superconducting materials and devices, condensed matter physics and low temperature physics
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
A. Kataria, J. A. T. Verezhak, O. Prakash, R. K. Kushwaha, A. Thamizhavel, S. Ramakrishnan, M. S. Scheurer, A. D. Hillier, and R. P. Singh
American Physical Society (APS)
Om Prakash, Anil Kumar, Samsher, Kumaresh Dey, and Ankish Aman
Elsevier BV
Asim Ahmad, Om Prakash, Anil Kumar, S.M. Mozammil Hasnain, Puneet Verma, Ali Zare, Gaurav Dwivedi, and Anukul Pandey
Elsevier BV
Om Prakash, Asim Ahmad, Anil Kumar, S.M. Mozammil Hasnain, Ali Zare, and Puneet Verma
Elsevier BV
Om Prakash, Bharath Bhushan, Anil Kumar, and Ankish Aman
Springer Nature Singapore
Asim Ahmad, Om Prakash, and Anil Kumar
Springer Nature Singapore
Arun Kumar Dwivedi, Anil Kumar, Prashant Baredar, and Om Prakash
Elsevier BV
Z. F. Weng, M. Smidman, G. M. Pang, O. Prakash, Y. Chen, Y. J. Zhang, S. Ramakrishnan, and H. Q. Yuan
American Physical Society (APS)
We report an investigation of the superconducting states of $\\mathrm{Lu}_3\\mathrm{Os}_4\\mathrm{Ge}_{13}$ and $\\mathrm{Y}_3\\mathrm{Ru}_4\\mathrm{Ge}_{13}$ single crystals by measurements of the electrical resistivity, ac susceptibility and London penetration depth. The analysis of the penetration depth and the derived superfluid density indicates the presence of nodeless superconductivity and suggest that there are multiple superconducting gaps in both materials. Furthermore, ac susceptibility measurements of both compounds display the peak effect in the low temperature region of the $H-T$ phase diagram. This anomalous increase of the critical current with field gives an indication of a change of the arrangement of flux lines in the mixed state, as found in some of the isostructural stannide materials.
Om Prakash, Anil Kumar, A. Thamizhavel, and S. Ramakrishnan
American Association for the Advancement of Science (AAAS)
Going cold with Bismuth Many elemental metals, such as lead and aluminum, become superconducting at low temperatures. Bismuth, a semimetal with very low carrier density, stays nonsuperconducting down to 10 mK. Prakash et al. performed tricky magnetization measurements to show that pure bulk bismuth does undergo the superconducting transition at a tiny temperature of about 0.5 mK (see the Perspective by Behnia). Because bismuth does not fit neatly into the standard picture of superconductivity, further theoretical work is necessary to explain the findings. Science , this issue p. 52 ; see also p. 26
Om Prakash, A. Thamizhavel, and S. Ramakrishnan
American Physical Society (APS)
We report site disorder driven ferromagnetic ordering of nearly 8$\\%$ Ce atoms in single crystalline Ce${_3}$Os${_4}$Ge$_{13}$ below 0.5~K. Ce${_3}$Os${_4}$Ge$_{13}$ crystallizes in a cubic structure with space group $\\it{Pm\\bar{3}n}$. The structural analysis shows the presence of site-disorder in the system, where 2(a) Ge site is partially occupied by the Ce atoms. Due to the small Ce $4f$-ligand hybridization, these Ce atoms are in the Ce$^{3+}$ (magnetic) state while rest of the Ce atoms in the unit cell are in Ce$^{4-\\delta}$ (non-magnetic) state. The heat capacity shows a peak below 0.5~K corresponding to the ferromagnetic ordering of the Ce$^{3+}$ moments. The ferromagnetic ordering below 0.5~K is also seen in the ac-susceptibility data. At low temperatures (1.8~K$\\leq T\\leq 6$~K), the magnetization shows $log(T)$ dependence, whereas the resistivity shows power law ($T^n$) temperature dependence indicating the non-Fermi liquid behavior of the quasiparticles.
Om Prakash, A Thamizhavel, and S Ramakrishnan
IOP Publishing
Intermetallic R3T4X13 series consist of a cage-like structure and have attracted attention due to their unconventional electronic ground states. In this work, we report the normal and superconducting state properties of a high-quality single crystal of Lu3Os4Ge13. Lu3Os4Ge13 belongs to the above-mentioned series and crystallizes in a cubic crystal structure with the space group Pm 3 ¯ n . Using electrical transport, magnetization and heat capacity measurements, we show that Lu3Os4Ge13 is a type-II multi-band superconductor (Tc = 3.1 K) with unusual superconducting properties. The analysis of the low-temperature heat capacity data suggests that Lu3Os4Ge13 is a moderately coupled multi-band BCS superconductor with two gaps ( 2 Δ / k B T c = 3.68 ± 0.04 & 0.34 ± 0.02 ) in the superconducting state. The dc-magnetization (M−H) shows a large reversible region in the superconducting state similar to the vortex liquid phase observed in high-Tc superconductors. The value of the Ginzburg number Gi suggests that the thermal fluctuations, though small compared to those in high-Tc cuprates, may play an important role in the unpinning of the vortices in this compound. The electronic band structure calculations show that three bands cross the Fermi level and constitute a complex Fermi surface in Lu3Os4Ge13.
Om Prakash, A Thamizhavel, and S Ramakrishnan
IOP Publishing
We report the normal and superconducting state properties of high quality single crystal of Lu3Os4Ge13 grown by Czochralski method. Lu3Os4Ge13 crystallises in the cubic crystal structure (space group Pm3n) . Lu3Os4Ge13 is a type-II superconductor (Tc = 3.1 K) as determined by the electrical transport, magnetisation and heat capacity measurements. The thermopower measurement shows a large phonon drag effect at low temperatures. The electronic band structure calculations show a multi-valley type band structure and a complex Fermi surface in Lu3Os4Ge13, making it a possible candidate to observe a magnetic field induced triplet superconductivity at ultra-low temperatures.
Om Prakash, A Thamizhavel, and S Ramakrishnan
IOP Publishing
A variety of unconventional superconductors have low carrier density as a common factor. However, the underlying mechanism of superconductivity in such low carrier density systems is not well understood. Besides, small carrier density is an unfavourable component for conventional superconductivity as described by the Bardeen-Cooper-Schrieffer (BCS) theory. Therefore, studying low carrier density systems can lead to a better understanding in such systems. In this paper, we report superconductivity property studies in low carrier density systems, Y3Ru4Ge13 and Lu3Os4Ge13, using various experimental techniques. Single crystals of Y3Ru4Ge13 and Lu3Os4Ge13 have been grown using the Czochralski crystal pulling method in a tetra-arc furnace. The x-ray diffraction experiment reveals that both compounds crystallize in cubic structure (space group Pm3n, no. 223). The transport, magnetization and heat capacity measurements show that Y3Ru4Ge13 single crystal undergoes a superconducting transition at 2.85 K, whereas, Lu3Os4Ge13 becomes superconductor at 3.1 K.
Om Prakash, A. Thamizhavel, A. K. Nigam, and S. Ramakrishnan
AIP Publishing LLC
Anil Kumar, Om Prakash, and S. Ramakrishanan
AIP Publishing LLC
A special sample measurement chamber has been developed to perform experiments at ultralow temperatures and ultralow magnetic field. A high permeability material known as cryoperm 10 and Pb is used to shield the measurement space consisting of the signal detecting set-up and the sample. The detecting setup consists of a very sensitive susceptibility coil wound on OFHC Cu bobbin.
Om Prakash, A. Thamizhavel, A.K. Nigam, and S. Ramakrishnan
Elsevier BV