Mott metal-insulator transition induced by utilizing a glass-like structural ordering in low-dimensional molecular conductors

Abstract

We utilize a glass-like structural transition in order to induce a Mott metal-insulator transition in the quasi-two-dimensional organic charge-transfer salt $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br. In this material, the terminal ethylene groups of the BEDT-TTF molecules can adopt two different structural orientations within the crystal structure, namely eclipsed (E) and staggered (S) with the relative orientation of the outer C$-$C bonds being parallel and canted, respectively. These two conformations are thermally disordered at room temperature and undergo a glass-like ordering transition at $T_g\sim 75$K. When cooling through $T_g$, a small fraction that depends on the cooling rate remains frozen in the S configuration, which is of slightly higher energy, corresponding to a controllable degree of structural disorder. We demonstrate that, when thermally coupled to a low-temperature heat bath, a pulsed heating current through the sample causes a very fast relaxation with cooling rates at $T_g$ of the order of several 1000K/min. The freezing of the structural degrees of freedom causes a decrease of the electronic bandwidth $W$ with increasing cooling rate, and hence a Mott metal-insulator transition as the system crosses the critical ratio $(W/U{)}_c$ of bandwidth to on-site Coulomb repulsion $U$. Due to the glassy character of the transition, the effect is persistent below $T_g$ and can be reversibly repeated by melting the frozen configuration upon warming above $T_g$. Both by exploiting the characteristics of slowly-changing relaxation times close to this temperature and by controlling the heating power, the materials can be fine-tuned across the Mott transition. A simple model allows for an estimate of the energy difference between the E and S state as well as the accompanying degree of frozen disorder in the population of the two orientations.

References in corpus (15)

• Mott transition, antiferromagnetism, and unconventional superconductivity in layered organic superconductors
• Quantum frustration in organic Mott insulators: from spin liquids to unconventional superconductors
• Unconventional critical behaviour in a quasi-two-dimensional organic conductor
• Evidence for structural and electronic instabilities at intermediate temperatures in $\kappa$-(BEDT-TTF)${}_2$X for X=Cu[N(CN)${}_2$]Cl, Cu[N(CN)${}_2$]Br and Cu(NCS)${}_2$: Implications for the phase diagram of these quasi-2D organic superconductors
• Transport criticality of the first-order Mott transition in a quasi-two-dimensional organic conductor, $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Cl
• The effect of irradiation-induced disorder on the conductivity and critical temperature of the organic superconductor $\kappa$-(BEDT-TTF)${}_2$Cu(SCN)${}_2$
• The Dependence of the Superconducting Transition Temperature of Organic Molecular Crystals on Intrinsically Non-Magnetic Disorder: a Signature of either Unconventional Superconductivity or Novel Local Magnetic Moment Formation
• Real space imaging of the metal - insulator phase separation in the band width controlled organic Mott system $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br
• Soft Hubbard gaps in disordered itinerant models with short-range interaction
• Electron localization near Mott transition in organic superconductor $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2]$Br
• Effective Coulomb interactions within BEDT-TTF dimers
• Determining ethylene group disorder levels in $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br
• Disorder Effect on the Vortex Pinning by the Cooling Process Control in the Organic Superconductor $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br
• Superconductor-Insulator Phase Separation Induced by Rapid Cooling in kappa-(ET)_2Cu[N(CN)_2]Br
• Suppression of superconductivity by non-magnetic disorder in organic superconductor $\kappa$-(BEDT-TTF)${}_2$Cu(NCS)${}_2$

Cited by in corpus (16)

• Critical Spin Liquid versus Valence Bond Glass in Triangular Lattice Organic $\kappa$-(ET)${}_2$Cu${}_2$(CN)${}_3$
• Near-degeneracy of extended $s+d_{x^2-y^2}$ and $d_{xy}$ order parameters in quasi-two-dimensional organic superconductors
• Evidence for eight node mixed-symmetry superconductivity in a correlated organic metal
• Influence of molecular conformations on the electronic structure of organic charge transfer salts
• Superconductivity in correlated BEDT-TTF molecular conductors: critical temperatures and gap symmetries
• Critical Slowing Down of the Charge Carrier Dynamics at the Mott Metal-Insulator Transition
• Origin of the glass-like dynamics in molecular metals $\kappa$-(BEDT-TTF)${}_{\text{2}}$X: implications from fluctuation spectroscopy and $\text{ab initio}$ calculations
• Effects of Disorder on the Pressure-Induced Mott Transition in $\kappa$-BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Cl
• Ingredients for Generalized Models of $\kappa$-Phase Organic Charge-Transfer Salts: A Review
• Insights from experiment and $abinitio$ calculations into the glass-like transition in the molecular conductor $\kappa$-(BEDT-TTF)${}_2$Hg(SCN)${}_2$Cl
• Coherent heavy charge carriers in an organic conductor near the bandwidth-controlled Mott transition
• Involvement of structural dynamics in the charge-glass formation in molecular metals
• Partially-ordered vortex lattices in the high-field, low-temperature mixed state of quasi two-dimensional organic superconductors
• Temperature dependent anisotropy and two-band superconductivity revealed by lower critical field in organic superconductor $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br
• Combined experimental and theoretical studies on glasslike transitions in the frustrated molecular conductors $\theta$-(BEDT-TTF)${}_{2}M{M}^{\prime }$(SCN)${}_4$
• Comparison of the charge-crystal and charge-glass state in geometrically frustrated organic conductors studied by fluctuation spectroscopy