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

Vianez, Pedro M. T. and Jin, Yiqing and Moreno, María and Anirban, Ankita S. and Anthore, Anne and Tan, Wooi Kiat and Griffiths, Jonathan P. and Farrer, Ian and Ritchie, David A. and Schofield, Andrew J. and Tsyplyatyev, Oleksandr and Ford, Christopher J. B. (2022) Observing separate spin and charge Fermi seas in a strongly correlated one-dimensional conductor. Science Advances, 8 (24): 2781. ISSN 2375-2548

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 tunneling 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 interaction strength is varied by changing the amount of 1D intersubband screening by more than 45%. Our findings not only demonstrate the existence of spin-charge separation in the whole energy band outside the low-energy limit of the Tomonaga-Luttinger model but also set a constraint on the validity of the newer nonlinear Tomonaga-Luttinger theory.