Low temperature charge order in IrTe₂ – searching for superconductivity with ultrafast optical pulses

Gregor Jecl
Department of Complex Matter, IJS

Abstract:

We have studied the charge ordered phases in IrTe₂, a van-der-Waals material in which superconductivity was shown to emerge either in thermally quenched nanoflakes, or in bulk samples where it competes with the Ir³⁺/Ir⁴⁺ dimerization induced stripe order and is stabilized by doping with Pt or Pd. Additionally, in pristine samples superconducting hexagonal surface patches, similar to those found in doped materials, were reported to form at three-fold striped phase intersections.

We have investigated the dynamics of the material in a broad range of temperatures and identified its structural phases, which are connected by first order phase transitions and exhibit a broad hysteresis loop in heating/cooling cycles. High fluence exposure at low temperatures results in non-thermal behavior where the increased anisotropy in amplitudes of relaxation components of  transient reflectivity might suggest enhanced order under exposure. A transition from the low-temperature to the middle-temperature phase is observed in three-pulse destruction-pump-probe measurements several picoseconds after the arrival of the destruction pulse, but no persistent changes are induced at this temperature. However, after subjecting the material to trains of high fluence laser pulses and imaging the surface in situ  in STM at helium temperature, healing of defects in the charge order, stabilization of the middle temperature phase and a change in orientation of the striped phase were observed.

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