Pressure-Tuned Exchange Coupling of a Quantum Spin Liquid in the Molecular Triangular Latticeκ−(ET)2Ag2<

Abstract

The effects of pressure on a quantum spin liquid are investigated in an organic Mott insulator κ-(ET)_{2}Ag_{2}(CN)_{3} with a spin-1/2 triangular lattice. The application of negative chemical pressure to κ-(ET)_{2}Cu_{2}(CN)_{3}, which is a well-known sister Mott insulator, allows for extensive tuning of antiferromagnetic exchange coupling, with J/k_{B}=175-310 K, under hydrostatic pressure. Based on ^{13}C nuclear magnetic resonance measurements under pressure, we uncover universal scaling in the static and dynamic spin susceptibilities down to low temperatures ∼0.1k_{B}T/J. The persistent fluctuations and residual specific heat coefficient are consistent with the presence of gapless low-lying excitations. Our results thus demonstrate the fundamental finite-temperature properties of a quantum spin liquid in a wide parameter range.

Importance of spin-orbit coupling in layered organic salts

“…The smallest J/J ∼ 0.3 belongs to κ-(ET) 2 B(CN) 4 , which exhibits quasi 1D (spin-liquid) behaviour down to T = 5 K [53]. The 2D spin-liquid candidates κ-(ET) 2 Cu 2 (CN) 3 [7,54] and κ-(ET) 2 Ag 2 (CN) 3 [9,55] have J/J ∼ 1 − 2, close to the triangular limit. The orientation of each DM-vector with respect to the ET molecules is shown in Fig.…”

Anion effects on electronic structure and electrodynamic properties of the Mott insulatorκ−(BEDT−TTF)2Ag2(CN)3Pinterić1, Lazić2, Pustogow3 et al. 2016Phys. Rev. B404860View full textAdd to dashboardCite

“…S1), although it remains valid on the global scale. 24 Another strong evidence is provided by vibrational spectroscopy: the ν 27 feature contains two Fano modes as opposed to only one in κ-CuCN. We explain this observation by a higher level of disorder related to P1 symmetry.…”

“…12 In order to elucidate the ferroelectric nature of QSL and advance the understanding of its dielectric response, the newly synthetized Mott dimer insulator κ-(BEDT-TTF) 2 Ag 2 (CN) 3 , 23 called κ-AgCN, has drawn our attention as recent NMR experiments have indicated a QSL ground state. 24 In this compound (Fig. 1) the anions also affect the overall electronic structure, but to a lower degree compared to κ-CuCN.…”

“…The first concerns the right wing of the peak centered at 300 K, which is attributed to ordering of the the ethylene group into eclipsed conformation. 24 Secondly, broad maxima are identified at about 85 to 65 K for all directions within and perpendicular to the planes. This feature may indicate the formation of a lowtemperature phase; the width of the peak suggests that it develops only on short length scales.…”

Design of Spin-Frustrated Monomer-Type C60•− Mott Insulator

“…Another organic QSL system of a dimer-type Mott insulator κ-(ET) 2 Ag 2 (CN) 3 (t /t = 0.97) was very recently developed by us (|Θ CW | = 263 K, |J|/k B = 175 K, f > 2.1 × 10 3 ) having a different key-keyhole relation from that of κ-(ET) 2 Cu 2 (CN) 3 resulting in both a more robust QSL state and a higher critical temperature (T c ) of SC than the X = Cu salt [54,65], with similar relaxor ferroelectric response [66,67]. Among these QSL systems, only dimer-type ET salts κ-(ET) 2 Cu 2 (CN) 3 and κ-(ET) 2 Ag 2 (CN) 3 manifest competition among the itinerancy of electrons (metal), pairing of two electrons (SC), and localization (Mott insulator and QSL).…”