Electron transmission through a short interacting wire: 0.7 conductance anomaly

Abstract

We investigate tunneling through a short interacting wire. We identify two temperature regimes (a) $T_{Kondo}<T\le T^{wire}=\hslash v_F/k_{B}d$ ($d$ is the length of the short wire) and (b) $T<T_{Kondo}\ll T^{wire}$. In the first regime the effective (renormalized) electron-electron interaction is smaller than the tunneling matrix element. This is the situation at finite temperature $T$ where the single particle spectrum of the wire is characterized by a multilevel "quantum dot" system with magnetic quantum number S=0 which is higher in energy than the SU(2) spin doublet $S=\pm 1/2$. Due to the single particle energy we find that the tunneling electron into the wire must have an opposite spin to the one in the short wire giving rise to a conductance, $G=G_{\uparrow }+G_{\downarrow }$, $e^2/h\le G\ll 2e^2/h$. In the second regime, when $T\to 0$ we have a situation that the effective (renormalized) electron-electron interaction is larger than the tunneling matrix element. This problem is equivalent to a Kondo problem. We find for $T<T_{Kondo}$ that the conductance is given by $G=2e^2/h$. These results are in agreement with recent experiments where for $T_{Kondo}<T<T^{wire}$ the conductance $G$ obeys $e^2/h\le G\ll 2e^2/h$, and for $T<T_{Kondo}$, $G=2e^2/h$. In both regimes the current is not polarized and the SU(2) symmetry is not broken.

40 pages plus two figures (to appear in Phys. Rev. B)

References in corpus (7)

• The Low-Temperature Fate of the 0.7 Structure in a Point Contact: A Kondo-like Correlated State in an Open System
• Kondo model for the "0.7 anomaly" in transport through a quantum point contact
• Density dependent spin polarisation in ultra low-disorder quantum wires
• Local moment formation in quantum point contacts
• The anomalous 0.5 and 0.7 conductance plateaus in quantum point contacts
• Persistent currents through a quantum dot
• Polarized Magnetic Wire Induced by Tunneling Through a Magnetic Impurity

Cited by in corpus (4)

• Electron-electron interaction effects in quantum point contacts
• Ferromagnetic Spin Coupling as the Origin of 0.7 Anomaly in Quantum Point Contacts
• Dirac's method for constraints - an application to quantum wires,the 0.7 conductance anomaly
• A Scaling Approach for Interacting Quantum Wires -a Possible Explanation for the 0.7 Anomalous Conductance