Time- and momentum-resolved gap dynamics inBi2Sr2CaCu2

Abstract

We use time-and angle-resolved photoemission spectroscopy to characterize the dynamics of the energy gap in superconducting Bi2Sr2CaCu2O 8+δ (Bi2212). Photoexcitation drives the system into a nonequilibrium pseudogap state: Near the Brillouin zone diagonal (inside the normal-state Fermi arc), the gap completely closes for a pump fluence beyond F ≈ 15 µJ/cm 2 ; toward the Brillouin zone face (outside the Fermi arc), it remains open to at least 24 µJ/cm 2 . This strongly anisotropic gap response may indicate multiple competing ordering tendencies in Bi2212. Despite these contrasts, the gap recovers with relatively momentum-independent dynamics at all probed momenta, which shows the persistent influence of superconductivity both inside and outside the Fermi arc.

Dynamics of superconducting order parameter through ultrafast normal-to-superconducting phase transition in Bi2Sr2CaCu2O8+δ

“…11 Considering the different doping levels of the samples and different spatial 42 and reciprocal-space 43 sensitivity of the probes only a qualitative correspondence between the results is expected, since even in the case of TR-ARPES the extraction of the SC gap is not rigorously defined 11 . For the sake of comparison we therefore assume that |ψ…”

“…The ultrafast S→N→S transition in the cuprate superconductors has been initially studied by all-optical [5][6][7][8][9] pump-probe technique followed by laser ARPES [10][11][12][13] . While the laser ARPES can directly resolve the momentum dependent 14 quasiparticle (QP) distribution function, all-optical techniques offer better bulk sensitivity and greater flexibility.…”

“…By means of the all-optical multi-pulse technique combined with the polarization selective optical probe we were able to separate the SC state recovery dynamics from the previously studied 22 PG state recovery dynamic and enable discrimination between relaxation in the nodal and anti-nodal BZ regions. The material has been studied previously by timeresolved techniques 7,8,[10][11][12]23 , but thus far there has been no systematic study of the the non-equilibrium transitions in this material, especially by the 3-pulse technique.…”

Photoinduced changes of the chemical potential in superconductingBi2Sr2CaCu2O8+δ

“…This energy gap is centered on the pair chemical potential [11], and studies on cuprate superconductor Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) show that the gap's size changes upon pumping [9,12,13]. Since * alanzara@lbl.gov only the lower edge of the gap is observed, it cannot be used to accurately measure the chemical potential.…”

“…Thus the manipulation of the chemical potential has many basic electronic applications; for example, a difference in the condensate energy across a Josephson junction drives an alternating supercurrent [1]. Ultrafast manipulation of the chemical potential with laser pump pulses has recently been realized by time-and angle-resolved photoemission spectroscopy (tr-ARPES) in several materials [2][3][4][5], including high-temperature superconductors [6][7][8][9].…”