Observing separate spin and charge Fermi seas in a strongly correlated one-dimensional conductor

TL;DR

This study provides experimental evidence of spin-charge separation across the entire energy spectrum in a 1D conductor, challenging the traditional low-energy limitations of the Tomonaga-Luttinger model.

Contribution

It reports the first observation of separate spin and charge Fermi seas at high energies in a strongly correlated 1D system using tunnelling spectroscopy.

Findings

Observation of two parabolic dispersions indicating separate spin and charge Fermi seas

Emergence of additional 1D 'replica' modes that grow with decreasing wire length

Effective interaction strength varied by over 45% through inter-subband screening

Abstract

An electron is usually considered to have only one form of kinetic energy, but could it have more, for its spin and charge, by exciting other electrons? In one dimension (1D), the physics of interacting electrons is captured well at low energies by the Tomonaga-Luttinger model, yet little has been observed experimentally beyond this linear regime. Here, we report on measurements of many-body modes in 1D gated-wires using tunnelling spectroscopy. We observe two parabolic dispersions, indicative of separate Fermi seas at high energies, associated with spin and charge excitations, together with the emergence of two additional 1D 'replica' modes that strengthen with decreasing wire length. The effective interaction strength is varied by changing the amount of 1D inter-subband screening by over 45%. Our findings demonstrate the existence of spin-charge separation in the whole energy band outside the low-energy limit of validity of the Tomonaga-Luttinger model, and also set a constraint on the validity of the newer nonlinear Tomonaga-Luttinger theory.