Optical freezing of charge motion in an organic conductor

Abstract

Dynamical localization, that is, reduction of the intersite electronic transfer integral t by an alternating electric field, E(o), is a promising strategy for controlling strongly correlated systems with a competing energy balance between t and the Coulomb repulsion energy. Here we describe a charge localization induced by the 9.3 MVcm À 1 instantaneous electric field of a 1.5 cycle (7 fs) infrared pulse in an organic conductor a-(bis[ethylenedithio]-tetrathiafulvalene) 2 I 3 . A large reflectivity change of 425% and a coherent charge oscillation along the time axis reflect the opening of the charge ordering gap in the metallic phase. This optical freezing of charges, which is the reverse of the photoinduced melting of electronic orders, is attributed to the B10% reduction of t driven by the strong, high-frequency (oZt/:) electric field.

Polarization selectivity of charge localization induced by a 7-fs nearly single-cycle light field in an organic metal

“…Thus, the polarization dependence of ( ) [15]. Here, we confirmed that the pr q dependence of / R R D at td=30 fs is analogous to that of the CO. indicates that the induced CO is neither a long-range order nor a local excited state [35] which is structurally stabilized, because it requires the timescale of intermolecular vibrations (> 100 fs) for stabilization.…”

“…1(a)) has been demonstrated in an organic metal a-(BEDT-TTF)2I3 with a triangular lattice [15]. Such transient localization of charge was originally motivated by "dynamical localization", i.e., the reduction of an effective transfer integral ( ) which is the time average of an original transfer integral t multiplied by the Peierls-phase factor (A(t): vector potential, rij: position vector for corresponding transfer process, T : period of the oscillating field) [16][17][18].…”

“…The central photon energy of the pump light is ~0.8 eV and the 5 probe range covers 0.58-0.95 eV. The method for generating the 7-fs pulse has been reported in the previous paper [15]. In this study, polarizations of both pump and probe pulses were controlled by a respective pair of wire-grid CaF2 polarizers as shown in Fig.…”

Photoinduced Enhancement of the Charge Density Wave Amplitude

“…Our results also raise fundamental questions regarding the dynamics of the magnetic ordering and the electronic structure of the system. Finally, we anticipate that the enhancement of an order parameter via dynamic interaction of various degrees of freedom is a general phenomenon and can be observed and studied both theoretically and experimentally in a variety of systems including topological insulators [45] and strongly correlated electron materials [8]. [23] simultaneously.…”

“…For instance, charge-lattice coupling creates chargedensity-wave (CDW) order [3,4], while more intricate spin-charge-orbital-lattice coupling leads to combined charge and orbital order in manganites [5,6], or charge-spin stripe order in cuprates [2]. Recent studies suggest that spin order can be generated in iron pnictides in response to excitation of a coherent phonon [7], charge localization can be photoinduced in charge order systems [8], the superconducting order parameter in cuprates can be enhanced via suppression of the competing charge order or the transient redistribution of superconducting coherence [9][10][11], and hidden electronic states can be dynamically accessed [12][13][14][15]. Here we demonstrate a dramatic transient enhancement of the CDW amplitude in elemental chromium (Cr) following photo-excitation.…”