Sagnac interference in Carbon nanotubes

TL;DR

This paper investigates Sagnac interference in carbon nanotubes, showing it persists under strong interactions and is less sensitive to temperature than Fabry-Perot interference, with potential for experimental observation.

Contribution

It provides a perturbative non-equilibrium analysis of Sagnac interference in nanotubes, highlighting its robustness against interactions and quantifying the temperature conditions for observation.

Findings

Sagnac interference remains stable under strong electron interactions.

The temperature for observing Sagnac interference is significantly higher than for Fabry-Perot.

Interference effects are weakly dependent on velocity detuning $u$.

Abstract

The Sagnac interference mode arises when two interfering counterpropogating beams traverse a loop, but with their velocities detuned by a small amount $2u$, with $v_{R/L}=v_F\pm u$. In this paper we perform a perturbative non-equilibrium calculation of Sagnac interference in single channel wires as well as armchair nanotube loops. We study the dependence of the Sagnac conductance oscillations on temperature and interactions. We find that the Sagnac interference is not destroyed by strong interactions, but becomes weakly dependent on the velocity detuning $u$. In armchairs nanotubes with typical interaction strength, $0.25 \leq g \leq 0.5$, we find that the necessary temperature for observing the interference effect, $T_{SAG}$ is also only weakly dependent on the interaction, and is enhanced by a factor of 8 relative to the temperature necessary for observing Fabry-Perot interference in the same system, $T_{FP}$.