Design and Preparation of a Quantum Spin Liquid Candidate κ-(ET)2Ag2(CN)3 Having a Nearby Superconductivity

Abstract

medal with purple ribbon awarded by the Government of Japan (2009). He has been devoted to the development of molecular compounds with π-systems bearing exotic functionality. AbstractSimilar to the first quantum spin liquid (QSL) candidate, ¬-(ET) 2 Cu 2 (CN) 3 (1), newly prepared ¬-(ET) 2 Ag 2 (CN) 3 (2) is a dimer Mott insulator with a QSL ground state at ambient pressure and exhibits metallic and superconducting states next to the QSL state under pressure, where ET is bis(ethylenedithio)tetrathiafulvalene. The packing of the ET dimer, which corresponds to a single spin site (S = 1/2), in 2 is similar to that in 1. Salt 2 afforded a two-dimensional equilateral triangular spin lattice having strong geometrical spin frustration (t¤/t = 0.967) similar to 1 (t¤/t = 1.09), where t and t¤ are the interdimer transfer interactions. The geometric relationship between the spin site and the opening in the anion layer in 2 is considerably different from that in 1, resulting in more dispersed packing of ET dimers, narrower bandwidth W, and larger on-site Coulomb repulsion energy U for 2 than 1. As a consequence, 2 has a higher electron correlation U/W, more robust QSL state for wider pressure range and is allocated far away from the itinerant region compared to those of 1. The narrower bandwidth is consistent with a higher superconducting critical temperature for 2 than 1 under pressure.

Anion effects on electronic structure and electrodynamic properties of the Mott insulatorκ−(BEDT−TTF)2Ag2(CN)3Pinterić1, Lazić2, Pustogow3 et al. 2016Phys. Rev. B414860View full textAdd to dashboardCite

“…Vibrational spectroscopy was performed on high-quality κ-AgCN single crystals 23 by an infrared microscope attached to the Fourier-transform interferometer. In Fig.…”

Thermal Expansion Studies on the Spin‐Liquid‐Candidate System κ‐(BEDT‐TTF)2Ag2(CN)3

“…Experimentally, no long‐range magnetic order was detected down to 110 mK which is three orders of magnitude lower than the dominant exchange coupling J / k B ≈ 175 K . From a structural point of view, the two compounds κ‐CuCN and κ‐AgCN are rather similar. Both compounds exhibit a monoclinic structure, however with distinctly different monoclinic angles (113.3° for κ‐CuCN vs. 91.3° for κ‐AgCN) .…”

“…Recently, the newly‐synthesized sister compound κ‐(ET) 2 Ag 2 (CN) 3 (abbreviated as κ‐AgCN hereafter) was proposed to be another good candidate for the realization of a quantum spin‐liquid ground state . Extended Hückel calculations of the hopping parameters suggest that in this compound the triangular lattice is almost isotropic with t′ / t = 0.97.…”

“…From a structural point of view, the two compounds κ‐CuCN and κ‐AgCN are rather similar. Both compounds exhibit a monoclinic structure, however with distinctly different monoclinic angles (113.3° for κ‐CuCN vs. 91.3° for κ‐AgCN) . The anion layers are in both cases formed by a network of zigzag chains along the b axis with site disorder in the linking CN groups (see Figure c).…”

“…The main structural difference is found in the relative orientation of the anion network with respect to the triangular lattice formed by the (ET) 2 + dimers, as outlined in detail in ref. . As a consequence, the ET molecules forming the dimers in κ ‐AgCN are packed less dense leading to a smaller bandwidth W ∝ t , t′ (and correspondingly, to smaller absolute values of J and J′ ), and thus a stronger correlation strength U / W …”