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EPR OF QUASIPARTICLES BY FLUCTUATIONS OF COOPER
PAIRS
Jan Stankowski
Institute of Molecular Physics, Polish Academy of
Sciences
Kazimierz Dolny 2005
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TRANSPORT PHENOMENA Microwave
Absorption (MA) was discovered in HTSC as a zero
field EPR line MA results from by Cooper pair
breaking when fluxes penetrate through a
Josephson weak links (JWL) Dynamics of the
field dependent MA implies, that flux flow, its
pinning and creep by 1o defects and 2o weak
contacts give the nonresonant AC
dissipation. AIM OF THIS WORK Electron
paramagnetic resonance - EPR in quasiparticles
system and sharp AC anomaly in field BEPR(f)
close to g0
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?0
VORTEX
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CURRENT INDUCED VORTEX MOTION CAUSE QP
FLUCTUATIONS
V J x ?
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CHEMICAL DEFECTS POTENTIAL IS B INDEPENDENT
JWC POTENTIAL IS PERIODICALY B DEPENDENT
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? n?0 ?0
? n?0 ?0
? n?0 ?0
? n?0
B
B
SC
U
WJL
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ANALYSIS OF AC ABSORPTION
Vortex motion (VM) model by Coffey and Clem
VM resistivity is due to
formation of quasiparticles (QP) In two-liquid
model nnQP 2nSC
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DISTRIBUTION OF CPs AND NORMAL ELECTRONS (QPs)
QP
CP
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MAGNETIC FIELD DEPENDENT AC ABSORPTION IN
SUPERCONDUCTORS
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ZERO FIELD ABSORPTION LINE FOR JWL
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HTSC RESISTIVITY VS. MAGNETIC FIELD
T80 K
T85 K
E. Silva et al., Int. J. of Modern Physics B, 17,
922 (2003)
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VORTEX MOTION HYSTERESIS LOOPS
AC ABSORPTION
DIFFERENTIAL MMMA SIGNAL
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VORTEX MOTION HYSTERESIS LOOP LC CIRCUIT FOR
22 MHz
?U
Magnetic field modulation (50Hz )
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MAGNETIC ANOMALY IN SLIGHTLY DOPED FULLERENE
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TWO PARAMAGNETIC CENTERS
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AMPLITUDE Ii OF THE EPR SIGNAL IN C60Rb

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SPIN EFFECT IN TRANSPORT PHENOMENA - EPR OF
QP in VMHL - BLOCH two coil EPR DETECTION -
EPR in MICROWAVE IMPEDANCE
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LC OSCILLATING CIRCUIT (22MHz)
sample
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JOSEPHSON HYSTERESIS LOOP IN LC CIRCUIT FOR 22
MHz
?U
50Hz B field modulation
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BLOCH NMR HEAD
Magnetic field
Receiving coil
Generating coil
15 MHz
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AC INDUCTION IN BLOCH TWO COIL METHOD
YBCO signal
DPPH strong sample
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NON-LINEAR VORTEX TO THE MAGNETIC FIELD
CuO2 plane
Magnetic Field
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AC DISSIPATION IN YBCO AT 21 GHz, from E. SILVA
J. Low Temp. Phys. , 131, 871 (2003)
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COMPUTER EXTRACTION OF THE SPIN SIGNAL FROM AC
DISSIPATION
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LOW FREQUENCE LIMIT g -factor close to
2 HIGH FREQUENCE g -factor for localized
state C601- ion in fullerene
and Cu2 - ion in YBCO
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CONCLUSIONS 1. FLUX MOTION GENERATING QP LEADS
TO NONRESONANT AC MAGNETIC FIELD
DISSIPATION 2. EPR OF NORMAL ELECTRONS (QP)
IS RELATED TO LOCALIZED SPIN STATE ON
PARAMAGNETIC CENTERS g?g0 SHOWING THAT
CONDUCTING CARRIERS ARE STRONGLY CORRELATED
ELECTRONS
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Low field study of EPR and paramagnetic
fluctuation can be used to study interaction
between local pairs (boson liquid) and
quasiparticles (quasi Fermi liquid).
T.Domanski, K.I.Wysokinski, Phys.Rev. B
66,064517-1 (2002)
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COLLABORATION R. Micnas - theory
advisor UAM IFM PAN J.
Martinek - theory of nonresonant MA W.
Kempinski - MMMA experiments L. Piekara-Sady
- fullerenes J. Grembowski - low freq.exp. W.
Bednarski - comuter expert
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THANKS FOR ATTENTION
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Institute of Molecular Physics, Polish Academy of
Sciences e-mail janstank_at_ifmpan.poznan.pl