Infrared spectroscopy study of the in-plane response of YBa_{2}Cu_{3}O_{6.6} in magnetic fields up to 30 Tesla

Abstract

With terahertz and infrared spectroscopy we studied the in-plane response of an underdoped, twinned YBa_{2}Cu_{3}O_{6.6} single crystal with T_{c}=58(1)K in high magnetic fields up to B=30 Tesla (T) applied along the c axis. Our goal was to investigate the field-induced suppression of superconductivity and to observe the signatures of the three-dimensional (3D) incommensurate copper charge density wave (Cu-CDW), which was previously shown to develop at such high magnetic fields. Our study confirms that a B field in excess of 20 T gives rise to a full suppression of the macroscopic response of the superconducting condensate. However, it reveals surprisingly weak signatures of the 3D Cu-CDW at high magnetic fields. At 30 T there is only a weak reduction of the spectral weight of the Drude-response (by about 3%), which is accompanied by an enhancement of the so-called mid-infrared (MIR) band as well as a narrow electronic mode around 240cm^{−1} (and, possibly, another one around 90cm^{−1}), which is interpreted in terms of a pinned phase mode of the CDW. The pinned phase mode and the MIR band are strong features already without magnetic field, which suggests that prominent but short-ranged and slowly fluctuating (compared to the picosecond infrared timescale) CDW correlations exist all along, i.e., even at zero magnetic field.