Time-Resolved Photoresponse Measurements of the Electrical Conductivity of the Quasi-Two-Dimensional Organic Superconductor β-(BEDT-TTF)2I3 Using a Nanosecond Laser Pulse

Time-resolved photoresponses in resistance have been measured following the nanosecond laser pulse excitation for the quasi-two-dimensional organic superconductors of hydrogenated and deuterated β-(BEDT-TTF)2I3 [BEDT-TTF = bis-(ethylenedithio)tetrathiafulvalene], which show two different superconducting states with high-Tc and low-Tc at temperatures near the critical temperatures. A transient increase of the resistance is induced by photoirradiation at all the temperatures, but a marked temperature dependence of the decay time is observed at temperatures close to the high-Tc phase transition temperature; the decay rate becomes faster and then becomes constant in both compounds, as the temperature decreases across the high-Tc phase transition temperature. The temperature dependence of the photoresponse intensity is different from the one expected from the bolometric effects, indicating the presence of the nonbolometric photoresponse. A possible mechanism explaining the photoresponse of the conductivity is discussed, based on the isotope effect on the photoresponse. A comparison is also made between β-(BEDT-TTF)2I3 and κ-(BEDT-TTF)2Cu[N(CN)2]Br for the transient photoresponse in resistance at temperatures across the metal-superconductor phase transition temperature

Insulator–Metal Transitions Induced by Electric Field and Photoirradiation in Organic Mott Insulator Deuterated κ-(BEDT-TTF)₂Cu[N(CN)₂]Br

The Mott insulator–metal transition induced by an external stimulus such as electric field, pressure, chemical doping, or photoirradiation has received considerable attention because of the potential use in new optoelectronic functional devices. Here we report an abrupt Mott insulator–metal transition observed as a current jump in a molecular-based Mott insulator, namely, deuterated κ-(BEDT-TTF)₂Cu­[N­(CN)₂]­Br, where BEDT-TTF = bis­(ethylenedithio)­tetrathiafulvalene, upon application of a pulsed voltage of certain magnitude (threshold voltage). Furthermore, the threshold voltage needed for the transition is shown to be reduced by photoirradiation. Thus, the Mott insulator–metal transition can be controlled by a combination of an external electric field and photoirradiation

Insulator–Metal Transitions Induced by Electric Field and Photoirradiation in Organic Mott Insulator Deuterated κ-(BEDT-TTF)₂Cu[N(CN)₂]Br

The Mott insulator–metal transition induced by an external stimulus such as electric field, pressure, chemical doping, or photoirradiation has received considerable attention because of the potential use in new optoelectronic functional devices. Here we report an abrupt Mott insulator–metal transition observed as a current jump in a molecular-based Mott insulator, namely, deuterated κ-(BEDT-TTF)₂Cu­[N­(CN)₂]­Br, where BEDT-TTF = bis­(ethylenedithio)­tetrathiafulvalene, upon application of a pulsed voltage of certain magnitude (threshold voltage). Furthermore, the threshold voltage needed for the transition is shown to be reduced by photoirradiation. Thus, the Mott insulator–metal transition can be controlled by a combination of an external electric field and photoirradiation

Time-Resolved Photoresponse Measurements of the Electrical Conductivity of the Quasi-Two-Dimensional Organic Superconductor β-(BEDT-TTF) 2

Time-resolved photoresponses in resistance have been measured following the nanosecond laser pulse excitation for the quasi-two-dimensional organic superconductors of hydrogenated and deuterated β-(BEDT-TTF)2I3 [BEDT-TTF = bis-(ethylenedithio)tetrathiafulvalene], which show two different superconducting states with high-Tc and low-Tc at temperatures near the critical temperatures. A transient increase of the resistance is induced by photoirradiation at all the temperatures, but a marked temperature dependence of the decay time is observed at temperatures close to the high-Tc phase transition temperature; the decay rate becomes faster and then becomes constant in both compounds, as the temperature decreases across the high-Tc phase transition temperature. The temperature dependence of the photoresponse intensity is different from the one expected from the bolometric effects, indicating the presence of the nonbolometric photoresponse. A possible mechanism explaining the photoresponse of the conductivity is discussed, based on the isotope effect on the photoresponse. A comparison is also made between β-(BEDT-TTF)2I3 and κ-(BEDT-TTF)2Cu[N(CN)2]Br for the transient photoresponse in resistance at temperatures across the metal-superconductor phase transition temperature