Unambiguous determination of the THz conductivity in driven YBa2Cu3O6+x
Abstract
Mid-infrared pump, THz probe experiments in YBa2Cu3O6+x yield evidence of a high-temperature transient state of the material with the optical properties of a superconductor. However, there are ambiguities in the extracted transient c-axis THz optical properties, primarily resulting from the sublinear growth of the THz response with increasing mid-infrared pump fluence. It was proposed that this effect may be related to saturation of the material's response, which would then perturb its spatial profile and lead one to overestimate the induced change in the transient optical properties. Yet, sublinear growth of the signal could also arise from other effects unrelated to saturation, for example from a change in reflectivity or deposition depth for the pump pulses. Here, we remove this ambiguity by experimentally measuring the fluence-dependent complex optical constants at the 15-20 THz frequencies of the pump. We show that the observed sublinear growth is to be attributed in large part to the enhanced reflection and reduced penetration depth of the pump field at high fluences. When taking into account these findings, we confirm the original interpretation of a light-induced superconducting state both qualitatively and quantitatively.
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BibTeX
@misc{kaj2026unambiguous,
title = {{Unambiguous determination of the THz conductivity in driven YBa$_2$Cu$_3$O$_6+x$}},
author = {K. Kaj and K. H. Martens and D. Choi and M. Buzzi and D. Nicoletti and Y. Liu and B. Keimer and A. Cavalleri},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.29892},
eprint = {2610.29892},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.29892},
}
RIS
TY - UNPB
TI - Unambiguous determination of the THz conductivity in driven YBa_2Cu_3O_6+x
AU - K. Kaj
AU - K. H. Martens
AU - D. Choi
AU - M. Buzzi
AU - D. Nicoletti
AU - Y. Liu
AU - B. Keimer
AU - A. Cavalleri
PY - 2026
DA - 2026/10/21
PB - arXiv
DO - 10.48550/arxiv.2610.29892
UR - https://arxiv.org/abs/2610.29892
AB - Mid-infrared pump, THz probe experiments in YBa_2Cu_3O_6+x yield evidence of a high-temperature transient state of the material with the optical properties of a superconductor. However, there are ambiguities in the extracted transient c-axis THz optical properties, primarily resulting from the sublinear growth of the THz response with increasing mid-infrared pump fluence. It was proposed that this effect may be related to saturation of the material's response, which would then perturb its spatial profile and lead one to overestimate the induced change in the transient optical properties. Yet, sublinear growth of the signal could also arise from other effects unrelated to saturation, for example from a change in reflectivity or deposition depth for the pump pulses. Here, we remove this ambiguity by experimentally measuring the fluence-dependent complex optical constants at the 15-20 THz frequencies of the pump. We show that the observed sublinear growth is to be attributed in large part to the enhanced reflection and reduced penetration depth of the pump field at high fluences. When taking into account these findings, we confirm the original interpretation of a light-induced superconducting state both qualitatively and quantitatively.
ER -