Microscopic origin of suppressed charge response in the competing metallic regime

Determine the microscopic mechanism responsible for the pronounced suppression of the Tomonaga–Luttinger liquid parameter K_rho and the associated reshaping of the low-energy charge response in the metallic regime of the one-dimensional doped t–J–K Kitaev–Heisenberg chain when the Heisenberg exchange J and Kitaev exchange K compete (i.e., have opposite signs).

Background

In the doped Kitaev–Heisenberg chain, the authors find that when the Heisenberg (J) and Kitaev (K) exchanges have opposite signs, their competition produces a strongly filling-dependent metallic regime with a substantially reduced Tomonaga–Luttinger liquid parameter K_rho, often K_rho ≲ 0.5. This regime sits adjacent to superconducting phases that emerge even for relatively small exchange couplings.

While the numerical results clearly reveal a strong suppression of K_rho and indicate that the competition between J and K exchanges reshapes the low-energy charge response, the microscopic mechanism underpinning this effect within the competing metallic regime is not yet understood, motivating a focused investigation of its origin.

References

More broadly, the pronounced suppression of K_\rho indicates that the competition between Kitaev and Heisenberg exchanges strongly reshapes the low-energy charge response. Clarifying the microscopic origin of this effect deep inside the competing metallic regime remains an interesting open problem.

— Ground State Properties of the Doped Kitaev-Heisenberg Chain: Topological Superconducting and Mott Insulating Phases Driven by Magnetic Frustration  (2603.29551 - Agrapidis et al., 31 Mar 2026) in Section 'Ground-state phase diagram of the doped Kitaev–Heisenberg chain', paragraph following Fig. 3 (Fig. \ref{fig:PD})