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

Powell, B. J. and McKenzie, Ross H. (2011) Quantum frustration in organic Mott insulators: From spin liquids to unconventional superconductors. Reports on Progress in Physics, 74 5: 056501.1-056501.60. doi:10.1088/0034-4885/74/5/056501


Author Powell, B. J.
McKenzie, Ross H.
Title Quantum frustration in organic Mott insulators: From spin liquids to unconventional superconductors
Journal name Reports on Progress in Physics   Check publisher's open access policy
ISSN 0034-4885
1361-6633
Publication date 2011-05
Sub-type Article (original research)
DOI 10.1088/0034-4885/74/5/056501
Volume 74
Issue 5
Start page 056501.1
End page 056501.60
Total pages 60
Place of publication Bristol, United Kingdom
Publisher Institute of Physics Publishing
Collection year 2012
Language eng
Formatted abstract
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.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Article # 056501

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
Official 2012 Collection
 
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Created: Mon, 05 Mar 2012, 14:03:29 EST by Dr Ben Powell on behalf of Physics