Hidden spin current in doped Mott antiferromagnets

TL;DR

This paper uncovers persistent spin currents in doped Mott insulators, revealing their connection to ground state degeneracy, charge/spin modulations, and the role of many-body Berry phases, with distinct behaviors for odd and even hole numbers.

Contribution

It demonstrates the existence of spin currents in doped Mott insulators and links them to ground state degeneracy and charge/spin patterns, highlighting novel many-body quantum phenomena.

Findings

Persistent spin currents are present in the ground state.

Ground state degeneracy is associated with nonzero total momentum or angular momentum.

Spin currents and charge/spin modulations vanish for even numbers of holes.

Abstract

We investigate the nature of doped Mott insulators using exact diagonalization and density matrix renormalization group methods. Persistent spin currents are revealed in the ground state, which are concomitant with a nonzero total momentum or angular momentum associated with the doped hole. The latter determines a nontrivial ground state degeneracy. By further making superpositions of the degenerate ground states with zero or unidirectional spin currents, we show that different patterns of spatial charge and spin modulations will emerge. Such anomaly persists for the odd numbers of holes, but the spin current, ground state degeneracy, and charge/spin modulations completely disappear for even numbers of holes, with the two-hole ground state exhibiting a d-wave symmetry. An understanding of the spin current due to a many-body Berry-like phase and its impact on the momentum distribution of the doped holes will be discussed.