Pumping spin, singlet pairs, and light
Open Access
- Author:
- Kim, Sungjun
- Graduate Program:
- Physics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 21, 2007
- Committee Members:
- Ari Mizel, Committee Chair/Co-Chair
Jainendra Jain, Committee Member
Nitin Samarth, Committee Member
Sharon Hammes Schiffer, Committee Member - Keywords:
- quantum pumping
spintronics
entanglement - Abstract:
- We apply quantum pumping to generate spin current, the flow of singlet pair, and the flow of light. We consider quantum pumping on two extended lattice models. We develop quantum pumping formula with single particle Green's functions. We find closed form for pumping formula in terms of full Green's functions. We present a prescription for generating pure spin current or spin selective current, based on quantum pumping in a 1-D tight-binding model. Our calculations indicate that some pumping cycles produce the maximum value 2 of pumped spin while others reverse the direction of current as a result of small alterations of the pumping cycle. We find pumping cycles which produce essentially any ratio of spin current to charge current. We propose a method to produce singlet pair flow by quantum pumping. We introduce Hubbard terms as pumping parameters. We extend our formalism to the interacting regime. We develop singlet pair pumping formula with two particle Green's function. We present plots which show how singlet pair flow depends on the size of squared cycle. We study interference effects in the current generated by quantum pumping in two extended lattice models. The first model contains an Aharonov-Bohm loop within a 1-D tight-binding model. It exhibits interference between the two arms of the loop. We also investigate the effect of magnetic field reversal on the pumped current. Our second model is a 1-D tight-binding model with next-nearest-neighbor hopping terms. The resulting band structure can have 4 degenerate Fermi wave vectors $pm k_{1F}$ and $pm k_{2F}$ rather than the usual 2 Fermi wave vectors $pm k_{F}$. It exhibits signatures of interference between these degenerate conduction band states. We propose a way to transport bosonic particle by pumping. We develop pumping formula based on Maxwell's equations. We choose localized time dependent dielectric constants as pumping parameters. By pumping, we generate net energy flow and its quantity can be precisely controlled by selecting pumping cycle.