Quantum ballistic transport by interacting two-electron states in quasi-one-dimensional channels

Abstract

For quantum ballistic transport of electrons through a short conduction channel, the role of Coulomb interaction may significantly modify the energy levels of two-electron states at low temperatures as the channel becomes wide. In this regime, the Coulomb effect on the two-electron states is calculated and found to lead to four split energy levels, including two anticrossing-level and two crossing-level states. Moreover, due to the interplay of anticrossing and crossing effects, our calculations reveal that the ground two-electron state will switch from one anticrossing state (strong confinement) to a crossing state (intermediate confinement) as the channel width gradually increases and then back to the original anticrossing state (weak confinement) as the channel width becomes larger than a threshold value. This switching behavior leaves a footprint in the ballistic conductance as well as in the diffusion thermoelectric power of electrons. Such a switching is related to the triple spin degeneracy as well as to the Coulomb repulsion in the central region of the channel, which separates two electrons away and pushes them to different channel edges. The conductance reoccurrence region expands from the weak to the intermediate confinement regime with increasing electron density.

Tunneling of hybridized pairs of electrons through a one-dimensional channel

“…When this coupling between wires becomes strong, the electron wave functions hybridize, forming bonding and antibonding states, which manifest as anticrossings in the 1D energy subbands. Our model calculations [15] further confirm that the minimum energy gap between the states occurs at the point of anticrossing but is not given by the energy difference between the symmetric and antisymmetric states.…”

“…Our model calculations 15 further confirm that the minimum energy gap between the states occurs at the point of anticrossing but is not given by the energy difference between the symmetric and antisymmetric states.…”

“…This may be verified by calculations of the kinetic, direct Coulomb, and exchange energies of electrons in wires with intermediate widths as well as for two extreme limits of very narrow and wide wires. In fact, we have recently demonstrated that these cases may be tracked down to the physical mechanism responsible for switching of the ground state as the wire width is varied from one value to another [15]. In the presence of the Coulomb interaction, two-electron states may be employed as a basis set for constructing the anticrossing-level states [1] when two electrons travel ballistically along a quasi-1D channel.…”

“…In the presence of the Coulomb interaction, two-electron states may be employed as a basis set for constructing the anticrossing-level states [1] when two electrons travel ballistically along a quasi-1D channel. The corresponding calculations have shown that the significance of the Coulomb induced level anticrossing within a quantum wire may be adjusted by varying the confinement potential with a top gate voltage [15].…”

Quantum phase transition detected through one-dimensional ballistic conductance

“…Reduction to an effective one-body problem through density functional theory [29], only accounts for the narrowing of the first plateau but does not explain its revival. Spin physics in a two-body scenario [30] has also been attempted, but it does not explain why the same anomaly is still present in spin polarized circumstances [26]. In fact, integer plateaus strongly indicates that the Landauer-Büttiker [31] paradigm should still be applicable with the sub-bands modified to be strongly correlated many-body states.…”