engleski

Charge transport in the disordered organic material κ-(BEDT-TTF)2Cu2(CN)3

The family of compounds based on bis-(ethylenedithio)tetrathiafulvalene (BEDT-TTF) molecule shows intriguing phenomena such as unconventional superconductivity, charge ordering, Mott transition, antiferromagnetism, incoherent metallic state etc. κ-(BEDT-TTF)2Cu2(CN)3 member is especially interesting because it is considered as one of the first realizations of a quantum spin liquid. It has a layered crystal structure consisting of conducting BEDT-TTF layers sandwiched between insulating Cu2(CN)3 layers and according to the phase diagram is in a Mott insulating state. However, approaching the spin liquid ground state various anomalies were observed showing that κ-(BEDT-TTF)2Cu2(CN)3 is not an ordinary Mott insulator. Here we present DC resistivity, Hall effect and magnetoresistance measurements for 10 K < T < 300 K and in magnetic fields up to 5 T on high quality κ-(BEDT-TTF)2Cu2(CN)3 single crystals. Our results clearly show that at lower temperatures (T < 130 K) charge transport takes place via variable range hopping, a mechanism typical for disordered systems. The origin of disorder, in nominally clean single crystals, can be found in insulating Cu2(CN)3 layers since some CN groups lie in centers of inversion and are therefore crystallographically disordered. The CN disorder affects conducting layers via hydrogen bonds between CN groups and ethylene groups of the BEDT-TTF molecules.

BEDT-TTF, quantum spin liquid, Mott insulator, magnetotransport, variable range hopping, disorder

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