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Papers by Dr. Neetu Agrawal

arXiv (Cornell University), Jun 1, 2012

RSC Advances, 2016

A novel strategy for the synthesis of highly ordered low-aspect ratio carbon nanocup arrays and i... more A novel strategy for the synthesis of highly ordered low-aspect ratio carbon nanocup arrays and its field emission properties.

Bulletin of the American Physical Society, Mar 21, 2013

in the two valleys. Thus, strain can induce a valley-dependent magnetic field. We investigate the... more in the two valleys. Thus, strain can induce a valley-dependent magnetic field. We investigate the combined effect of commensurate scalar and vector potentials on a pair of region of uniform uniaxial strain. The strained region induces opposite gauge potentials leading to a valley dependence of the transverse velocity of incident valley unpolarised beam, while quasibound states arising due to well formation between the double unit structure give rise to giant lateral shifts. Thus lateral displacement of transmitted beams from K and K ′ valleys together with their difference can be enhanced to a very large extent thereby enabling a highly efficient valley beam splitting. The wide tunability of proposed device is facilitated due to the presence of external vector potential. This vector potential acts in a similar way at the two valleys, thereby providing a handle to manipulate the net effect of strain.

Journal of Physics: Condensed Matter, 2014

In the absence of a magnetic field, scattered wavefunction inside a circular p-n junction in grap... more In the absence of a magnetic field, scattered wavefunction inside a circular p-n junction in graphene exhibits an interference pattern with high intensity maximum located around the caustics. We investigate the wavefunctions in the presence of a uniform magnetic field outside the circular region to show how the loci of the high intensity region changes by forming Landau level structure outside the circular region and a central high intensity region inside the circular p-n junction due to the strong reflection of massless Dirac fermions by the outside magnetic field. We conclude by suggesting experimental ways to detect such change of pattern due to the effect of the magnetic field.

International Journal of Modern Physics B, 2013

In this review article we discuss the recent progress in studying ballistic transport for charge ... more In this review article we discuss the recent progress in studying ballistic transport for charge carriers in graphene through highly inhomogeneous magnetic field known as magnetic barrier in combination with gate voltage induced electrostatic potential. Starting with cases for a single or double magnetic barrier we also review the progress in understanding electron transport through the superlattices created out of such electromagnetic potential barriers and discuss the possibility of experimental realization of such systems. The emphasis is particularly on the analogy of such transport with propagation of light wave through medium with alternating dielectric constant. In that direction we discuss electron analogue of optical phenomena like Fabry–Perot resonances, negative refraction, Goos–Hänchen effect, beam collimation in such systems and explain how such analogy is going to be useful for device generation. The resulting modification of band structure of Dirac fermions, the emerg...

The European Physical Journal B, 2013

We consider the transmission of massless Dirac fermions through an array of short range scatterer... more We consider the transmission of massless Dirac fermions through an array of short range scatterers which are modelled as randomly positioned δ-function like potentials along the x-axis. We particularly discuss the interplay between disorder-induced localization that is the hallmark of a non-relativistic system and two important properties of such massless Dirac fermions, namely, complete transmission at normal incidence and periodic dependence of transmission coefficient on the strength of the barrier that leads to a periodic resonant transmission. This leads to two different types of conductance behavior as a function of the system size at the resonant and the off-resonance strengths of the delta function potential. We explain this behavior of the conductance in terms of the transmission through a pair of such barriers using a Green's function based approach. The method helps to understand such disordered transport in terms of well known optical phenomena such as Fabry Perot resonances.

Journal of Physics: Condensed Matter, 2012

Whereas massless Dirac fermions in monolayer graphene exhibit Klein tunneling when passing throug... more Whereas massless Dirac fermions in monolayer graphene exhibit Klein tunneling when passing through a potential barrier upon normal incidence, such a barrier totally reflects massive Dirac fermions in bilayer graphene due to difference in chirality. We show that, in the presence of magnetic barriers, such massive Dirac fermions can have transmission through even at normal incidence. The general consequence of this behaviour for multilayer graphene consisting of massless and massive modes are mentioned. We also briefly discuss the effect of a bias voltage on such magnetotransport.

arXiv (Cornell University), Jun 1, 2012

RSC Advances, 2016

A novel strategy for the synthesis of highly ordered low-aspect ratio carbon nanocup arrays and i... more A novel strategy for the synthesis of highly ordered low-aspect ratio carbon nanocup arrays and its field emission properties.

Bulletin of the American Physical Society, Mar 21, 2013

in the two valleys. Thus, strain can induce a valley-dependent magnetic field. We investigate the... more in the two valleys. Thus, strain can induce a valley-dependent magnetic field. We investigate the combined effect of commensurate scalar and vector potentials on a pair of region of uniform uniaxial strain. The strained region induces opposite gauge potentials leading to a valley dependence of the transverse velocity of incident valley unpolarised beam, while quasibound states arising due to well formation between the double unit structure give rise to giant lateral shifts. Thus lateral displacement of transmitted beams from K and K ′ valleys together with their difference can be enhanced to a very large extent thereby enabling a highly efficient valley beam splitting. The wide tunability of proposed device is facilitated due to the presence of external vector potential. This vector potential acts in a similar way at the two valleys, thereby providing a handle to manipulate the net effect of strain.

Journal of Physics: Condensed Matter, 2014

In the absence of a magnetic field, scattered wavefunction inside a circular p-n junction in grap... more In the absence of a magnetic field, scattered wavefunction inside a circular p-n junction in graphene exhibits an interference pattern with high intensity maximum located around the caustics. We investigate the wavefunctions in the presence of a uniform magnetic field outside the circular region to show how the loci of the high intensity region changes by forming Landau level structure outside the circular region and a central high intensity region inside the circular p-n junction due to the strong reflection of massless Dirac fermions by the outside magnetic field. We conclude by suggesting experimental ways to detect such change of pattern due to the effect of the magnetic field.

International Journal of Modern Physics B, 2013

In this review article we discuss the recent progress in studying ballistic transport for charge ... more In this review article we discuss the recent progress in studying ballistic transport for charge carriers in graphene through highly inhomogeneous magnetic field known as magnetic barrier in combination with gate voltage induced electrostatic potential. Starting with cases for a single or double magnetic barrier we also review the progress in understanding electron transport through the superlattices created out of such electromagnetic potential barriers and discuss the possibility of experimental realization of such systems. The emphasis is particularly on the analogy of such transport with propagation of light wave through medium with alternating dielectric constant. In that direction we discuss electron analogue of optical phenomena like Fabry–Perot resonances, negative refraction, Goos–Hänchen effect, beam collimation in such systems and explain how such analogy is going to be useful for device generation. The resulting modification of band structure of Dirac fermions, the emerg...

The European Physical Journal B, 2013

We consider the transmission of massless Dirac fermions through an array of short range scatterer... more We consider the transmission of massless Dirac fermions through an array of short range scatterers which are modelled as randomly positioned δ-function like potentials along the x-axis. We particularly discuss the interplay between disorder-induced localization that is the hallmark of a non-relativistic system and two important properties of such massless Dirac fermions, namely, complete transmission at normal incidence and periodic dependence of transmission coefficient on the strength of the barrier that leads to a periodic resonant transmission. This leads to two different types of conductance behavior as a function of the system size at the resonant and the off-resonance strengths of the delta function potential. We explain this behavior of the conductance in terms of the transmission through a pair of such barriers using a Green's function based approach. The method helps to understand such disordered transport in terms of well known optical phenomena such as Fabry Perot resonances.

Journal of Physics: Condensed Matter, 2012

Whereas massless Dirac fermions in monolayer graphene exhibit Klein tunneling when passing throug... more Whereas massless Dirac fermions in monolayer graphene exhibit Klein tunneling when passing through a potential barrier upon normal incidence, such a barrier totally reflects massive Dirac fermions in bilayer graphene due to difference in chirality. We show that, in the presence of magnetic barriers, such massive Dirac fermions can have transmission through even at normal incidence. The general consequence of this behaviour for multilayer graphene consisting of massless and massive modes are mentioned. We also briefly discuss the effect of a bias voltage on such magnetotransport.