prashant shahi - Academia.edu (original) (raw)

Papers by prashant shahi

Physica Scripta, 2021

Structural, pressure-dependent resistivity, angle resolved photoemission spectroscopy (ARPES), x-... more Structural, pressure-dependent resistivity, angle resolved photoemission spectroscopy (ARPES), x-ray photoelectron diffraction (XPD) and band structure by DFT calculation have been investigated for BiSbTe3 Topological insulator. It has been demonstrated that the Dirac point of the topological surface state (TSS) located exactly at the Fermi level. Additionally, superconductivity emerges under pressure of 8 GPa with a critical temperature of ∼2.5 K. With further increase of pressure, the superconducting transition temperature (Tc) increases and at 14 GPa it shows the maximum Tc (∼3.3 K). It has also been shown that the surface state remains unchanged under pressure and has been suggested that the origin of the superconductivity is due to the bulk state. The investigation indicates that the BiSbTe3 has robust surface states and becomes superconductor under pressure.

Proceedings of the National Academy of Sciences

× 10 4 cm 2 •V-1 •s-1 " should instead appear as "1.3 × 10 5 cm 2 •V-1 •s-1 "; and, on page 9939,... more × 10 4 cm 2 •V-1 •s-1 " should instead appear as "1.3 × 10 5 cm 2 •V-1 •s-1 "; and, on page 9939, left column, first paragraph, lines 8-9, "4.4 nm-2 at 1 GPa, ∼26.8 nm-2 at 2 GPa, and ∼65.8 nm-2 at 3 GPa" should instead appear as "∼0.044 nm-2 at 1 GPa, ∼0.268 nm-2 at 2 GPa, and ∼0.658 nm-2 at 3 GPa." The authors also note that, on page 9937, right column, first paragraph, line 4, "(16)" should instead appear as "(21)." Lastly, the authors note that Fig. 3 appeared incorrectly. The corrected figure and its legend appear below.

arXiv: Superconductivity, 2019

We have grown single-crystal BiSbTe3 3D TI sample and studied structural, TE as well as pressure ... more We have grown single-crystal BiSbTe3 3D TI sample and studied structural, TE as well as pressure dependent magneto-transport properties. Large positive Seebeck coefficient confirmed the p-type nature of BiSbTe3, which is consistent with Hall measurement. We have also studied the electronic band structure using Laser-based ARPES, which revealed the existence of a Dirac-cone like metallic surface state in BiSbTe3 with a Dirac Point situated exactly at the Fermi level. Additionally, superconductivity emerges under pressure of 8 GPa with a critical temperature of ~2.5 K. With further increase of pressure, the superconducting transition temperature (Tc) increases and at 14 GPa it shows the maximum Tc (~3.3 K).

Scientific Reports

The magneto-transport, magnetization and theoretical electronic-structure have been investigated ... more The magneto-transport, magnetization and theoretical electronic-structure have been investigated on type-II Weyl semimetallic MoTeP. The ferromagnetic ordering is observed in the studied sample and it has been shown that the observed magnetic ordering is due to the defect states. It has also been demonstrated that the presence of ferromagnetic ordering in effect suppresses the magnetoresistance (MR) significantly. Interestingly, a change-over from positive to negative MR is observed at higher temperature which has been attributed to the dominance of spin scattering suppression.

arXiv: Strongly Correlated Electrons, 2014

The structural, magnetic and transport properties have been studied of Li doped CoV2O4 and FeV2O4... more The structural, magnetic and transport properties have been studied of Li doped CoV2O4 and FeV2O4. Li doping increases the ferri-magnetic ordering temperature of both the samples but decreases the spin-glass transition temperature of CoV2O4. The Li-doping decreases the V-V distance which in effect increases the A-V coupling. Thus the increased A-V coupling dominate over the decrease in A-V coupling due to doping of non-magnetic Li.

International Journal of Current Research and Review

The range of progesterone levels are 100-200 ng/ml and the amount produced by placenta is about 2... more The range of progesterone levels are 100-200 ng/ml and the amount produced by placenta is about 250 mg/day. 5,6 There is

Physical Review B

Ag 4 (CN) 5 [ET = BEDT-TTF: bis(ethylenedithio)tetrathiafulvalene] is a rare example of organic c... more Ag 4 (CN) 5 [ET = BEDT-TTF: bis(ethylenedithio)tetrathiafulvalene] is a rare example of organic conductors that crystallizes in a diamond structure due to the tetrahedral arrangement of neighboring ET molecules. Because each ET has a +1 site charge, the band is half filled, which in combination with strong Coulomb interactions, turn (ET)Ag 4 (CN) 5 into a Mott insulator. Recently, it was realized that this material may realize a nodal Dirac semimetal with a diamondlike lattice, whose state can be induced by suppressing the strong electron correlations. In this report, we present high pressure transport and optical studies on (ET)Ag 4 (CN) 5. Our transport study indicates that the activation energy is highly suppressed by the application of hydrostatic pressure. At high pressures, the system varies from activated behavior into Coulomb gap variable range hopping.

Proceedings of the National Academy of Sciences of the United States of America, Oct 2, 2018

We report a thorough study of the transport properties of the normal and superconducting states o... more We report a thorough study of the transport properties of the normal and superconducting states of black phosphorus (BP) under magnetic field and high pressure with a large-volume apparatus that provides hydrostatic pressure to induce transitions from the layered A17 phase to the layered A7 phase and to the cubic phase of BP. Quantum oscillations can be observed at ≥ 1 GPa in both resistivity and Hall voltage, and their evolutions with pressure in the A17 phase imply a continuous enlargement of Fermi surface. A significantly large magnetoresistance (MR) at low temperatures is observed in the A7 phase that becomes superconducting below a superconducting transition temperature ∼ 6-13 K. increases continuously with pressure on crossing the A7 to the cubic phase boundary. The strong MR effect can be fit by a modified Kohler's rule. A correlation between and fitting parameters suggests that phonon-mediated interactions play dominant roles in driving the Cooper pairing, which is furth...

Materials Research Express, 2015

The structural, magnetic, electrical and transport properties of FeV 2 O 4 , by doping Li and Cr ... more The structural, magnetic, electrical and transport properties of FeV 2 O 4 , by doping Li and Cr ions respectively in A and B sites, have been studied. Dilution of A-site by Li doping increases the ferri-magnetic ordering temperature and decreases the ferroelectric transition temperature. This also decreases the V-V distances which in effect increases the A-V coupling. This increased A-V coupling dominates over the decrease in A-V coupling due to doping of non-magnetic Li. On the other hand, Cr doping increases the ferri-magnetic ordering temperature but does not alter the ferroelectric transition temperature which is due to the fact that the polarization origin to the presence of almost non-substituted regions.

Co doped ZnV2O4 has been investigated by Synchrotron X-ray diffraction, Magnetization measurement... more Co doped ZnV2O4 has been investigated by Synchrotron X-ray diffraction, Magnetization measurement and Extended X-ray absorption fine structure (EXAFS) analysis. With Co doping in the Zn site the system moves towards the itinerant electron limit. From Synchrotron and magnetization measurement it is observed that there is an effect in bond lengths and lattice parameters around the magnetic transition temperature. The EXAFS study indicates that Co ion exists in the High spin state in Co doped ZnV2O4.

Materials Chemistry and Physics, 2015

ABSTRACT Induction of short range ferromagnetic ordering has been observed in the quasi one dimen... more ABSTRACT Induction of short range ferromagnetic ordering has been observed in the quasi one dimensional antiferromagnetic LiCuVO4 system with doping of Mn in the octahedral (Cu) site. Though, magnetic ordering is not stable enough as further increase of Mn-concentration, magnetic ordering gets deteriorated. This might be the case that Mn2+ ions, with strong magnetic moment as compared to Cu2+ ions, enhance the ferromagnetic coupling between the nearest neighbor atoms of quasi-one-dimensional magnetic LiCuVO4 system. Ferromagnetic ordering in LiCu0.95Mn0.05VO4 system also degraded after high energy ion beam excitation which creates defects and may disturb the short range ferromagnetic ordering in its near locality but it does not have much effect on the long range antiferromagnetic ordering. Irradiation causes no change in Raman modes of LiCu0.95Mn0.05VO4 system, while it produces some new vibrational modes in intermediate and high frequency region of LiCu0.9Mn0.1VO4 system. Above results have been understood based on competitions between ferromagnetic nearest neighbor (NN) coupling and antiferromagnetic next nearest neighbor (NNN) coupling in CuO2 chain.

The chemical pressure effect on the structural, transport, magnetic and electronic properties (by... more The chemical pressure effect on the structural, transport, magnetic and electronic properties (by measuring X-ray photoemission spectroscopy) of ZnV 2 O 4 has been investigated by doping Mn and Co on the Zinc site of ZnV 2 O 4. With Mn doping the V-V distance increases and with Co doping it decreases. The resistivity and thermoelectric power data indicate that as the V-V distance decreases the system moves towards Quantum Phase Transition. The transport data also indicate that the conduction is due to the small polaron hopping. The chemical pressure shows the non-monotonous behaviour of charge gap and activation energy. The XPS study also supports the observation that with decrease of the V-V separation the system moves towards Quantum Phase Transition. On the other hand when Ti is doped on the V-site of ZnV 2 O 4 the metal-metal distance decreases and at the same time the T N also increases.

$Research paper thumbnail of Magnetic and Structural properties of $ MnV_ {2} O_ {4} $$

Magnetization, neutron diffraction and X-ray diffraction of Zn doped MnV 2 O 4 as a function of t... more Magnetization, neutron diffraction and X-ray diffraction of Zn doped MnV 2 O 4 as a function of temperature have been measured and the critical exponents and magnetocaloric effect of this system have been estimated. It is observed, that with increase in Zn substitution the noncollinear orientation of Mn spins with the V spins decreases which effectively leads to the decrease of structural transition temperature more rapidly than Curie temperature. It has been shown that the obtained values of β, γ and δ from different methods match very well. These values do not belong to universal class and the values are in between the 3D Heisenberg model and mean field interaction model. The magnetization data follow the scaling equation and collapse into two branches indicating that the calculated critical exponents and critical temperature are unambiguous and intrinsic to the system. The observed double peaks in magneto-caloric curve of Mn 0.95 Zn 0.05 V 2 O 4 is due to the strong distortion of VO 6 octahedra.

Science of Advanced Materials, 2015

AIP Advances, 2014

ABSTRACT X-ray absorption near edge spectra (XANES) and magnetization of Zn doped MnV2O4 have bee... more ABSTRACT X-ray absorption near edge spectra (XANES) and magnetization of Zn doped MnV2O4 have been measured and from the magnetic measurement the critical exponents and magnetocaloric effect have been estimated. The XANES study indicates that Zn doping does not change the valence states in Mn and V. It has been shown that the obtained values of critical exponents \b{eta}, {\gamma} and {\delta} do not belong to universal class and the values are in between the 3D Heisenberg model and the mean field interaction model. The magnetization data follow the scaling equation and collapse into two branches indicating that the calculated critical exponents and critical temperature are unambiguous and intrinsic to the system. All the samples show large magneto-caloric effect. The second peak in magneto-caloric curve of Mn0.95Zn0.05V2O4 is due to the strong coupling between orbital and spin degrees of freedom. But 10% Zn doping reduces the residual spins on the V-V pairs resulting the decrease of coupling between orbital and spin degrees of freedom.