Quantum frustration in organic Mott insulators: from spin liquids to unconventional superconductors

By B. Powell, R. McKenzie. 2010

263 citations recorded by the source corpus.

We review the interplay of frustration and strong electronic correlations in quasi-two-dimensional organic charge transfer salts, such as (BEDT-TTF)2X and EtnMe4−nPn[Pd(dmit)2]2. These two forces drive a range of exotic phases including spin liquids, valence bond crystals, pseudogapped metals and unconventional superconductivity. Of particular interest is that in several materials pressure drives a first-order transition from a spin liquid Mott insulating state to a superconducting state. Experiments on these materials raise a number of profound questions about the quantum behaviour of frustrated systems, particularly the intimate connection between spin liquids and superconductivity. Insights into these questions have come from a wide range of theoretical techniques including first principles electronic structure, quantum many-body theory and quantum field theory. In this review we introduce some of the basic ideas of the field by discussing a simple frustrated Heisenberg model with four spins. We then describe the key experimental results, emphasizing that for two materials, κ-(BEDT-TTF)2Cu2(CN)3 and EtMe3Sb[Pd(dmit)2]2, there is strong evidence for a spin liquid ground state, and for another, EtMe3P[Pd(dmit)2]2, there is evidence of a valence bond crystal ground state. We review theoretical attempts to explain these phenomena, arguing that they can be captured by a Hubbard model on the anisotropic triangular lattice at half filling, and that resonating valence bond wavefunctions capture most of the essential physics. We review evidence that this Hubbard model can have a spin liquid ground state for a range of parameters that are realistic for the relevant materials. In particular, spatial anisotropy and ring exchange are key to destabilizing magnetic order. We conclude by summarizing the progress made thus far and identifying some of the key questions still to be answered.

Subfields: Condensed Matter Physics, Electronic, Optical and Magnetic Materials

View Paper: https://www.semanticscholar.org/paper/f67cd63bae8b0345c1d71bbf08204bd2a0b89ec3

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Condensed Matter Physics

1. T. Senthil
2. Yi Zhou
3. T. Ng
4. Ashvin Vishwanath
5. K. Kanoda
6. H. Po
7. R. Cava
8. Steven A. Kivelson

In Electronic, Optical and Magnetic Materials

1. Yi Zhou
2. T. Ng
3. Ashvin Vishwanath
4. K. Kanoda
5. T. Senthil
6. R. McKenzie
7. B. Powell

Citations in the corpus

• Origin of Mott Insulating Behavior and Superconductivity in Twisted Bilayer Graphene (2018, background): “The most famous are the cuprate high-Tc materials [1]; others include layered organic materials [2], certain fullerene superconductors [3], and some iron-based superconductors [4].”
• Quantum spin liquids (2019, background): “They are (i) 2D organic salts such as k-(ET2)Cu2(CN)3 and EtMe3Sb[Pd(dmit)2]2, where structural dimers possessing a single spin-1⁄2 degree of freedom form a triangular lattice (70); (ii) herbertsmithite (and the closely related Zn-barlowite), where the Cu ions form a kagome lattice (71); and (iii) a”
• Quantum spin liquid states (2016, methodology): “As the anti-bonding band is half-filled and the Coulomb repulsive energy is comparable to the band width, the family of κ-(ET)2X is good model system to study Mott physics (Kanoda, 1997a,b; Kino and Fukuyama, 1995; Powell and McKenzie, 2011; Shimizu et al., 2006).”