arXiv subjects

Sanjay Prabhakar

Publications and source records attributed to Sanjay Prabhakar.

21 records · Page 2Linked to original sources

arXiv2011

Manipulation of single electron spin in a GaAs quantum dot through the application of geometric phases: The Feynman disentangling technique

The spin of a single electron in an electrically defined quantum dot in a 2DEG can be manipulated by moving the quantum dot adiabatically in a closed loop in the 2D plane under the influence of applied gate potentials. In this paper we present analytical expressions and numerical simulations for the spin-flip probabilities during the adiabatic evolution in the presence of the Rashba and Dresselhaus linear spin-orbit interactions. We use the Feynman disentanglement technique to determine the non-Abelian Berry phase and we find exact analytical expressions for three special cases: (i) the pure Rashba spin-orbit coupling, (ii) the pure Dresselhause linear spin-orbit coupling, and (iii) the mixture of the Rashba and Dresselhaus spin-orbit couplings with equal strength. For a mixture of the Rashba and Dresselhaus spin-orbit couplings with unequal strengths, we obtain simulation results by solving numerically the Riccati equation originating from the disentangling procedure. We find that the spin-flip probability in the presence of the mixed spin-orbit couplings is generally larger than those for the pure Rashba case and for the pure Dresselhaus case, and that the complete spin-flip takes place only when the Rashba and Dresselhaus spin-orbit couplings are mixed symmetrically.

cond-mat.mes-hall↗

arXiv2011

Manipulation of the Land$\acute{\text{e}}$ g-factor in InAs quantum dots through the application of anisotropic gate potentials: Exact diagonalization, numerical and perturbation methods

We study the variation in the Land$\acute{\text{e}}$ g-factor of electron spins induced by both anisotropic gate potentials and magnetic fields in InAs quantum dots for possible implementation towards solid state quantum computing. In this paper, we present analytical expressions and numerical simulations of the variation in the Land$\acute{\text{e}}$ g-factor for both isotropic and anisotropic quantum dots. Using both analytical techniques and numerical simulations, we show that the Rashba spin-orbit coupling has a major contribution in the variation of the g-factor with electric fields before the regime, where level crossing or anticrossing occurs. In particular, the electric field tunability is shown to cover a wide range of g-factor through strong Rashba spin-orbit interaction. Another major result of this paper is that the anisotropic gate potential gives quenching effect in the orbital angular momentum that reduces the variation in the E-field and B-field tunability of the g-factor if the area of the symmetric and asymmetric quantum dots is held constant. We identify level crossings and anticrossings of the electron states in the variation of the Land$\acute{\text{e}}$ g-factor. We model the wavefunctions of electron spins and estimate the size of the anticrossing for the spin states $|0,-1,+1/2>$ and $|0,0,-1/2>$ corresponding to a quantum dot that has been recently studied experimentally (Phys. Rev. Lett. \textbf{104}, 246801 (2010)).

cond-mat.mes-hall↗

arXiv2008

Gate control of a quantum dot single-electron spin in realistic confining potentials: anisotropy effects

Among recent proposals for next-generation, non-charge-based logic is the notion that a single electron can be trapped and its spin can be manipulated through the application of gate potentials. In this paper, we present numerical simulations of such spins in single electron devices for realistic (asymmetric) confining potentials in two-dimensional electrostatically confined quantum dots. Using analytical and numerical techniques we show that breaking the in-plane rotational symmetry of the confining potential leads to a significant effect on the tunability of the g-factor with applied gate potentials. In particular, anisotropy extends the range of tunability to larger quantum dots.

cond-mat.mes-hall↗