New Type of Degenerate Quantum Spin Phase

TL;DR

This paper presents numerical evidence for a novel nonmagnetic insulating phase in 2D frustrated Mott insulators, characterized by gapless spin excitations and ground state degeneracy, suggesting a new type of quantum spin liquid.

Contribution

It introduces a new quantum spin liquid phase near the Mott transition with unique properties, expanding understanding of frustrated magnetic systems.

Findings

Identification of a nonmagnetic insulating phase with gapless excitations

Ground state degeneracy across the Brillouin zone

Relevance to experimental frustrated magnet materials

Abstract

Correlated electrons often crystalize to the Mott insulator usually with some magnetic orders, whereas the "quantum spin liquid" has been a long-sought issue. We report numerical evidences that a nonmagnetic insulating (NMI) phase gets stabilized near the Mott transition with remarkable properties: The 2D Mott insulators on geometrically frustrated lattices contain a phase with gapless spin excitations and degeneracy of the ground state in the whole Brillouin zone of the total momentum. It has an interpretation for an unexplored type of a quantum liquid. The present concept is useful in analyzing a variety of experimental results in frustrated magnets including organic BEDT-TTF compounds.