Anomalous Local Transport in MicrofabricatedSr2RuO4-Ru Eutectic Junction

2009. 9. 4 NDSN2009@Nagoya Univ.AISTHiroshi KambaraSatoshi Kashiwaya

Tokyo Univ of Sci. Hiroshi YaguchiHokkaido Univ.Yasuhiro AsanoNagoya Univ.Yukio TanakaKyoto Univ.Yoshiteru Maeno

IntroductionHow is the local transport property?

If chiral domain exists, how is the transport property affected?Sr2RuO4 (Tc=1.5 K)

Chiral p-wave superconductor(spin-triplet pairing)Measurement of local transport characteristics of Sr2RuO4-Ru eutectic junction made by microfabrication.Observation of anomalous hysteresis in V-I

Sr2RuO4-Ru eutectic system ~3-K phase superconductivity~Sr2RuO4 Ru eutecticsMaeno et al., PRL 81, 3765 (1998).p-wave superconducting junction is naturally formed.

Extract a channel of Sr2RuO4-Ru junctionFocusing on the local superconducting channelby controlling the number of Ru-inclusionsKink structures appearafter FIB milling becauseonly a few channels are left.If microbridge is thin and narrow enough.

dV/dI-I characteristics Model of Josephson junctions in seriesTTc00Each channelS-S-SS-N-SIc0Ic1Ic2

Parity of the 3-K phasespsss0p03-K phase is also p-wave.( 1.5-K phase is p-wave.)ss00Monotonic increase of IcT > Tc0T < Tc0

Sample configuration (I // ab and I // c)

Anomalous hysteresis is observed for both I//ab and I//c direction.V-I & dV/dI-I characteristics (Anomalous hysteresis) I // ab

How are V-I characteristics anomalous?Anomalous features Voltage decreases at Isw. It switches to a lower Rn (normal resistance) branch with larger Ic.

(3) Opposite hysteresis loop compared to typical Josephson junction (JJ) s.Sr2RuO4-Ru

Magnetic field effectcf) Hc1(0) 70 G (1.5-K phase) Deguchi, Mao, Maeno, JPSJ(2004). sample 1 NO influence of vortices !FCZFCNo change in the hysteresis between FC and ZFC.H // c

Possible origin of the hysteresis

Possible origin of the anomalous hysteresisdomain wall motion variation of cross section variation of IcRupx+ipypx-ipyRuinitial stateIcIcSfilament (parallel domain) NO hysteresis

IcSDW (antiparallel domain) Hysteresis!(a) Inhomogeneous channel model

Possible origin of the anomalous hysteresis (b) 3-K phase+1.5-K phase coexistence model (kx or ky) (kxiky)(3) I = Isw Ic largerAssuming 3-K phase symmetry (kx) along the edge because of broken translational symmetry.

Questions for the chiral domain model

Summary of the anomalous hysteresis HysteresisInhomogeneous channelModel3-K + 1.5-K(kx) (kx+iky)VortexI // abI // c?No-magnetic field effectOK!probably OK?questioncontrarytotalMultiple switchChiral domainVortex origin is ruled out.

Local transport measurements have been done (I//ab, I//c) for Sr2RuO4-Ru eutectic samples made by FIB process. p-wave Josephson junctions are formed (3-K / 1.5-K / 3-K).

Anomalous hysteresis was observed for both current directions. (voltage drop, opposite hysteresis loop) Chiral domain is a possible origin with (a) Inhomogeneous channel model or (b) 3-K phase+1.5-K phase model or others?

Summary

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