Searcharxiv⌕ Search

arXiv subjects

Prashant Sharma

Publications and source records attributed to Prashant Sharma.

31 records · Page 2Linked to original sources
arXiv2015

A parameterized model for Coulomb barrier height

Coulomb barrier height is a basic parameter to describing the nuclear reactions. Recently it is found that ions produce from nuclear reactions can be used to study electron loss and capture processes. Hence determining the Coulomb barrier becomes important in both nuclear and atomic physics. The different models depend on the nucleus-nucleus potential chosen or parameters used to calculate the barrier heights. In this work we plan to develop a parameterized formula from experimental results obtained from quasi elastic scattering. Since quasi elastic data spread over Z1Z2=64 to Z1Z2=2460, the formula is expected to work in the range of low Z1Z2 to high Z1Z2, where Z1, Z2 are the atomic number of the projectile and the target, respectively.

nucl-th↗
arXiv2015

X-Ray Spectroscopy: An Experimental Technique to Measure Charge State Distribution Right at the Ion-Solid Interaction

Charge state distributions of $^{56}$Fe and $^{58}$Ni projectile ions passing through thin carbon foils have been studied in the energy range of 1.44 - 2.69 MeV/u using a novel method from the x-ray spectroscopy technique. Interestingly the charge state distribution in the bulk show Lorentzian behavior instead of usual Gaussian distribution. Further, different parameters of charge state distribution like mean charge state, distribution width and asymmetric parameter are determined and compared with the empirical calculations and ETACHA predictions. It is found that the x-ray measurement technique is appropriate to determine the mean charge state right at the interaction zone or in the bulk. Interestingly, empirical formalism predicts much lower projectile mean charge states compare to x-ray measurements which clearly indicate multi-electron capture from the target surface. The ETACHA predictions and experimental results are found to be comparable for energies $\geq$ 2 MeV/u.

physics.atom-ph↗
arXiv2015

Shaking during Ion-Atom Collisions

Shaking (shakeup + shakeoff) probabilities accompanying ion-atom collisions are studied using hydrogenic wavefunctions for K-, L-, M- shell electrons in the sudden approximation limit. The role of recoil velocity in the shaking processes is discussed. Further, it is found that the suddenness of collision between projectile and target nuclei plays a major factor in shaking of respective atomic system than the recoil of nuclei.

physics.atom-ph↗
arXiv2015

Strong Evidence of Plasma-like Behavior for Ion-Solid Collisions

Charge state distributions of various projectile ions passing through thin carbon foils have been studied in the energy range of 0.7-3.0 MeV/u using x-ray spectroscopy. This technique is found to be appropriate to segregate the charge state distribution in the bulk from that of the surface by measuring the charge changing phenomena right at the interaction zone i.e. at t=0. This observation has been confirmed by different theoretical approaches. Surprisingly, it is found that the charge state distribution measured in the bulk, exhibits Lorentzian profile which is an important characteristic of any plasma. The occurrence of such behaviour suggests that ion-solid collisions constitute tenuous plasma in the bulk of the solid target. Thus, this work is expected to have practical implications in various fields, in particular, plasma physics and astrophysics.

physics.plasm-ph↗
arXiv2005

Spin current as a response to external stress

It is theoretically predicted that a traveling shear wave will create a spin current in certain direct-gap (for example III-V compound) semiconductors with contributions from both the valence bands and the conduction band (for $n$-doped semiconductors). We show that this spin-current is a property of the Fermi-Dirac sea, and is controlled by a geometric phase accumulated by the strain-induced Rashba parameters in a cycle.

cond-mat.mes-hall↗
arXiv2005

Semiclassical ordering in the large-N pyrochlore antiferromagnet

We study the semiclassical limit of the $Sp(N)$ generalization of the pyrochlore lattice Heisenberg antiferromagnet by expanding about the $N \to \infty$ saddlepoint in powers of a generalized inverse spin. To leading order, we write down an effective Hamiltonian as a series in loops on the lattice. Using this as a formula for calculating the energy of any classical ground state, we perform Monte-Carlo simulations and find a unique collinear ground state. This state is not a ground state of linear spin-wave theory, and can therefore not be a physical (N=1) semiclassical ground state.

cond-mat.str-el↗
arXiv2004

Mesoscopic effects in adiabatic spin pumping

We show that temporal shape modulations (pumping) of a quantum dot in the presence of spin-orbital coupling lead to a finite dc spin current. Depending on the strength of the spin-orbit coupling, the spin current is polarized perpendicular to the plane of the two-dimensional electron gas, or has an arbitrary direction subject to mesoscopic fluctuations. We analyze the statistics of the spin and charge currents in the adiabatic limit for the full cross-over from weak to strong spin-orbit coupling.

cond-mat.mes-hall↗
arXiv2003

Anomalous spin transport in a two-channel-Kondo quantum dot device

We study the response of a two-channel Kondo quantum dot device proposed by Y. Oreg and D. Goldhaber-Gordon [Phys. Rev. Lett. {\bf 90}, 136602 (2003)] to a spin-bias applied across one of its channels formed by Fermi liquid reservoirs weakly coupled to a spin-1/2 quantum dot. When the temperature $T<T_K$, the Kondo temperature of the device, the spin conductance depends on the Kondo coupling of the dot spin to the other channel in an anomalous manner. For isotropic Kondo couplings to the two channels the spin conductance is quantized for $T\ll T_K$ characterizing the two-channel Kondo fixed point. On the other hand, for anisotropic couplings a crossover energy scale $T_A\neq 0$ determines the temperature $T\ll T_A$ when the spin conductance vanishes indicating one-channel Kondo behavior.

cond-mat.mes-hall↗
arXiv2003

On the scaling approach to electron-electron interactions in a chaotic quantum dot

A scaling theory is used to study the low energy physics of electron-electron interactions in a double quantum dot. We show that the fact that electrons are delocalized over two quantum dots does not affect the instability criterion for the description of electron-electron interactions in terms of a ``universal interaction Hamiltonian''.

cond-mat.mes-hall↗
arXiv2002

Adiabatic charge and spin transport in interacting quantum wires

We study charge and spin transport through an interacting quantum wire, caused by backscattering off an effective impurity potential with a periodic time-dependence. The adiabatic regime of this pump for charge and spin is shown to depend on the presence of interactions in the wire. Using symmetry and scaling properties of the quantum wire Hamiltonian we relate the charge $Q$ and spin $S$ transported through the wire in a period to an integral involving quasi-static backscattering conductances. We also show that the pumped charge $Q$ (or the spin $S$) is quantized in the adiabatic limit if the conductance of the system is zero at the stable fixed point of the renormalization-group (RG) transformations. By contrast, for a RG marginal conductance -- which is the case for non-interacting electrons -- the charge transported in a cycle is non-universal. Finite size, temperature, and frequency effects on the transported quantities follow from the relation between adiabatic transport coefficients (backscattering conductances) and the quasi-static conductance of the system.

cond-mat.mes-hall↗
arXiv2001

Non-equilibrium tunneling into general quantum Hall edge states

In this paper we formulate the theory of tunneling into general Abelian fractional quantum Hall edge states. In contrast to the simple Laughlin states, a number of charge transfer processes must be accounted for. Nonetheless, it is possible to identify a unique value corresponding to dissipationless transport as the asymptotic large-$V$ conductance through a tunneling junction, and find fixed points (CFT boundary conditions) corresponding to this value. The symmetries of a given edge tunneling problem determine the appropriate boundary condition, and the boundary condition determines the strong-coupling operator content and current noise.

cond-mat.mes-hall↗
arXiv2000

Quantum pump for spin and charge transport in a Luttinger liquid

We study two different parametric pumps for interacting quantum wires, one for pumping spin currents, the other for charge currents. We find that the spin or charge pumped per cycle has a non-universal crossover, depending on pumping details, between two universal fixed point values of 0 and twice the electronic spin or charge quantum number. These universal values are independent of interactions, but the direction of flow between the two values depends on whether the interactions are repulsive or attractive.

cond-mat.mes-hall↗