Cooper pair breaking dynamics in MgB2 using optical-pump terahertz-probe spectroscopy

Conference · Thu Jan 01 04:00:00 EST 2004

OSTI ID:977846

Demsar, J ^[1]; Averitt, R D ^[2]; Kabanov, V V

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1. Jure
2. Richard D.

Cooper pair-breaking dynamics (PBD) have been resolved for the first time in MgB{sub 2}. We present an analysis of the PBD using the Rothwarf-Taylor model, enabling the determination of the bare quasiparticle recombination and phonon pair-breaking rates. Nonequilibrium effects have been studied in superconductors since the 1960's. One of the primary goals of such investigations has been to determine the bare quasiparticle recombination rate. However, directly measuring this rate is difficult since, as first noted by Rothwarf and Taylor, other phenomena contribute to the measurements. In the case of superconductors, the bare quasiparticle recombination rate is masked due to pair-breaking by above gap phonons. To date, it has not been possible to extract the bare quasiparticle recombination rate. In the case of conventional superconductors, one problem is that the superconducting transition temperatures are quite low, making detailed fluence dependent measurements all but impossible. However, with the discovery of MgB{sub 2} (T{sub c} = 39K) it is now possible to perform detailed fluence dependent ultrafast measurements on a conventional (i.e. phonon mediated pairing) superconductor. Our recent experiments of the picosecond photoinduced far-infrared conductivity dynamics on MgB{sub 2} have, for the first time, revealed the dynamics of Cooper pair breaking following photoexcitation. Here we present a detailed analysis of the pair breaking dynamics which suggests that in MgB{sub 2} photoexcitation is initially followed by energy relaxation to high frequency phonons instead of, as commonly assumed, e-e thermalization. Furthermore, the bare quasiparticle recombination rate and the probability for pair-breaking by phonons have been determined for the first time.

• Research Organization: Los Alamos National Laboratory
• Sponsoring Organization: DOE
• OSTI ID: 977846
• Report Number(s): LA-UR-04-6265
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COOPER PAIRS
PHONONS
PROBABILITY
RECOMBINATION
RELAXATION
SPECTROSCOPY
SUPERCONDUCTORS
THERMALIZATION
TRANSITION TEMPERATURE