Ballistic exciton transistor
An excitonic device comprises an exciton transmission line comprised of a row of molecules. Propagation of excitons is mediated by an exciton exchange interaction. The gate consists of a molecule “a” that interacts with a proximal molecule via a two-body exciton interaction. If the gate molecule is not excited, it does not couple to the transmission line thereby allowing incoming signals to propagate unimpeded. If the gate molecule is excited, signals are back scattered as a result of the two-body interaction between the exciton residing on “a” and the excitons on the transmission line. The ballistic exciton transistor has industrial applications that extend to at least fast optical switching, optical communication, exciton devices, and exciton-based information processing.
1. An excitonic device comprising:
an exciton transmission line composed of a row of chromophores through which signals can propagate, each chromophore of the row of chromophores being excitable from a ground state to a lowest electronic excited state;
a gate molecule having a transition dipole moment oriented orthogonally to dipoles along the exciton transmission line;
the gate molecule and the chromophore in the transmission line most proximal to the gate molecule, at a minimum, are asymmetric and possess a difference static dipole;
an excitonic interchange comprising:
a first location at which a linear exciton exchange interaction can occur, said linear exciton exchange interaction mediated by a transition dipole along the exciton transmission line; and
a second location at which a two-body exciton interaction can occur, said two-body exciton mediated by a difference static dipole along the transmission line.
2. The excitonic device of claim 1 wherein the gate molecule comprises a dye.
3. The excitonic device of claim 2 wherein the linear exciton exchange has a strength characterized by an excitonic hopping parameter, said excitonic hopping parameter being dependent on a dye orientation and proximity relative to the chromophores in the exciton transmission line.
4. The excitonic device of claim 1 wherein the two-body exciton interaction has a strength characterized by, at least in part, an excitonic state parameter, an exciton-exciton interaction energy, that accounts for whether the gate molecule is in a ground state or an excited state.
5. The excitonic device of claim 1 wherein the device is configured as an optical switch or an on/off gate wherein:
(i) when the gate molecule is not excited, transmission of said signals along the exciton transmission line occurs unimpeded; and
(ii) when the gate molecule is excited, said signals are backscattered as a result of the two-body exciton interaction.
6. The excitonic device of claim 1 wherein a direction of the transition dipoles and the difference static dipole are not parallel in at least the gate molecule or the chromophore in the transmission line most proximal to the gate molecule.
7. The excitonic device of claim 1 wherein transfer of excitons from the gate molecule to the exciton transmission line is prevented.
8. The excitonic device of claim 1 wherein the gate molecule can be excited optically without exciting the row of chromophores if polarized light with a polarization parallel to the transition dipole moment is used.
9. The excitonic device of claim 1 wherein the gate molecule can be excited optically without exciting the row of chromophores if the optical excitation energies of the gate molecule and the row of chromophores are chosen so that (i) an absorption band of the gate molecule does not overlap with that of the row of chromophores and (ii) a wavelength of light, regardless of polarization, lies only within the absorption band.
10. The excitonic device of claim 1 wherein the components of the excitonic device are symmetrically arranged about an axis defined by the gate molecule and a chromophore within the row of chromophores proximal to the gate molecule.
11. A ballistic exciton transistor relying on an exciton exchange interaction and a two-body exciton interaction, said ballistic exciton transistor comprising:
an exciton exchange interaction mediated by transition dipoles;
a two-body exciton interaction is mediated by the difference static dipoles;
a first chromophore and a second chromophore oriented such that the first chromophore and the second chromophore can interact only via the two-body exciton interaction;
an exciton transmission line comprising at least the second chromophore, a third chromophore, and a fourth chromophore;
wherein transition dipoles of the first chromophore and the second chromophore are arranged such that the transition dipoles do not couple.
12. The ballistic exciton transistor of claim 11 wherein the first chromophore and the second chromophore comprise asymmetric organic dye molecules.
13. The ballistic exciton transistor of claim 11 wherein the first chromophore has a transition dipole moment oriented orthogonally to dipoles along the exciton transmission line.
14. The ballistic exciton transistor of claim 11 wherein the two-body exciton interaction is mediated by a Coulombic quadrupole-quadruple interaction.
15. The ballistic exciton transistor of claim 11 wherein:
the third chromophore is located at an upstream location relative to the second chromophore with respect to how signals propagate along the exciton transmission line; and
the fourth chromophore is located at a downstream location relative to the second chromophore with respect to how signals propagate along the exciton transmission line.
16. The ballistic exciton transistor of claim 11 wherein when the first chromophore is excited by absorption of a photon, an exciton is trapped on the first chromophore and additional excitons are backscattered along the exciton transmission line, thereby providing a signal gain.