Title: Ultrafast Gap Dynamics and Electronic Interactions in a Photoexcited Cuprate Superconductor

Abstract

We perform time- and angle-resolved photoemission spectroscopy (trARPES) on optimally doped Bi₂Sr₂CaCu₂O_8+δ (BSCCO-2212) using sufficient energy resolution (9 meV) to resolve the k-dependent near-nodal gap structure on time scales where the concept of an electronic pseudotemperature is a useful quantity, i.e., after electronic thermalization has occurred. We study the ultrafast evolution of this gap structure, uncovering a very rich landscape of decay rates as a function of angle, temperature, and energy. We explicitly focus on the quasiparticle states at the gap edge as well as on the spectral weight inside the gap that “fills” the gap—understood as an interaction, or self-energy effect—and we also make high resolution measurements of the nodal states, enabling a direct and accurate measurement of the electronic temperature (or pseudotemperature) of the electrons in the system. Rather than the standard method of interpreting these results using individual quasiparticle scattering rates that vary significantly as a function of angle, temperature, and energy, we show that the entire landscape of relaxations can be understood by modeling the system as following a nonequilibrium, electronic pseudotemperature that controls all electrons in the zone. Furthermore, this model has zero free parameters, as we obtain the crucial information of the SC gapmore » Δ and the gap-filling strength Γ_TDoS by connecting to static ARPES measurements. The quantitative and qualitative agreement between data and model suggests that the critical parameters and interactions of the system, including the pairing interactions, follow parametrically from the electronic pseudotemperature. In conclusion, we expect that this concept will be relevant for understanding the ultrafast response of a great variety of electronic materials, even though the electronic pseudotemperature may not be directly measurable.« less

Authors:

Parham, S.; Li, H.; Nummy, T. J.; Waugh, J. A.; Zhou, X. Q.; Griffith, J.; Schneeloch, J.; Zhong, R. D.; Gu, G. D.; Dessau, D. S.

Publication Date:

2017-10-20

Research Org.:

Brookhaven National Lab. (BNL), Upton, NY (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1400429

Alternate Identifier(s):

OSTI ID: 1412782

Report Number(s):

BNL-114804-2017-JA
Journal ID: ISSN 2160-3308; PRXHAE; 041013

Grant/Contract Number:  

SC0112704; SC0012704

Resource Type:

Published Article

Journal Name:

Physical Review. X

Additional Journal Information:

Journal Name: Physical Review. X Journal Volume: 7 Journal Issue: 4; Journal ID: ISSN 2160-3308

Publisher:

American Physical Society

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY