Quantum spin liquids by geometric lattice design

TL;DR

This paper reports the discovery of a potential quantum spin liquid state in a specially designed heterostructure with enhanced magnetic frustration, showing no spin order down to very low temperatures.

Contribution

It introduces a new two-dimensional heterostructure that significantly increases magnetic frustration and demonstrates no spin ordering, suggesting a quantum spin liquid state.

Findings

Enhanced magnetic frustration in the heterostructure compared to bulk crystals

Absence of spin ordering down to 30 mK

Potential realization of a quantum spin liquid state

Abstract

On a lattice composed of triangular plaquettes where antiferromagnetic exchange interactions between localized spins cannot be simultaneously satisfied, the system becomes geometrically frustrated with magnetically disordered phases remarkably different from a simple paramagnet. Spin liquid belongs to one of these exotic states, in which a macroscopic degeneracy of the ground state gives rise to the rich spectrum of collective phenomena. Here, we report on the discovery of a new magnetic state in the heterostructures derived from a single unit cell (111)-oriented spinel CoCr2O4 sandwiched between nonmagnetic Al2O3 spacers. The artificial quasi-two-dimensional material composed of three triangle and one kagome atomic planes shows a degree of magnetic frustration which is almost two orders of magnitude enlarged compared to the bulk crystals. Combined resonant X-ray absorption and torque magnetometry measurements confirm that the designer system exhibits no sign of spin ordering down to 30 mK, implying a possible realization of a quantum spin liquid state in the two dimensional limit.