Edge States ofSr2RuO4Detected by In-Plane Tunneling Spectroscopy

Abstract

We perform tunneling spectroscopy of Sr 2 RuO 4 searching for the edge states peculiar to topological superconductivity. Conductance spectra obtained on Sr 2 RuO 4 /Au junctions fabricated using in situ process show broad humps indicating the successful detection of a-axis edge of 1.5K phase. Three types of peak shape are detected: domelike peak, split peak and two-step peak. By comparing the experiments with predictions for unconventional superconductivity, these varieties are shown to originate from multiband chiral p-wave symmetry with weak anisotropy of pair amplitude. The broad hump in conductance spectrum is a direct manifestation of the edge state peculiar to the chiral p-wave superconductivity.Since the discovery of the ruthenate superconductor Sr 2 RuO 4 (SRO) [1], the symmetry of the pair potential has been a topic of hot debate. The high anisotropy of transport properties indicates the quasi-two-dimensional electronic states of this compound. Nuclear magnetic resonance [2] and muon spin resonance experiments [3] suggest spin triplet pairing states with broken 1

Enhanced spin-triplet superconductivity near dislocations in Sr2RuO4

“…Tunneling spectra obtained at an in-plane magnetic field of 40 mT, at which the superconductivity in Al counter electrodes is suppressed, feature zero-bias conductance peaks (ZBCPs). Such ZBCPs were observed in Sr 2 RuO 4 previously 23,24 , and linked to the p-wave pairing symmetry. For sample D (onset T c ¼ 2.5 K), the ZBCP was visible at 2.2 K, with its shape varying as the temperature is lowered (Fig.…”

Suppression of spontaneous currents inSr2RuO4by surface disorder

“…ab faces of Sr 2 RuO 4 can be cleaved, but ac and bc faces are typically polished to a smoothness of several nm 9 , on the order of ten lattice constants. In a-axis junction tunneling conductance measurements, signatures of superconductivity at the surface are present only at the sub-1% level on top of a substantial smooth background 17 , as shown in Fig. 2 of that reference.…”

“…We focus narrowly on spontaneous currents here, though a calculation of quantities such as the tunneling conductance (to compare with ref. 17) within a more realistic model will be important in evaluating the consistency of the present scenario with experiment.…”

“…Motivated by a-axis tunneling experiments 17 , we employ a different interface condition than previous studies, modeling the surface region as a normal metal layer adjoining the superconducting bulk. We find that, compared to previous estimates, the expected magnetic signal from edge currents is reduced by over an order of magnitude.…”

Ferromagnetic features of zero-bias conductance peaks in a ferromagnet/insulator/superconductor junction

“…al. [27] has shown the ZBCP which is direct evidence of the ZABS by tunneling spectroscopic experiment of Sr 2 RuO 4 -Au junction. There is much interest and importance to investigate problems on spin triplet p-wave symmetry nature because the p-wave pairing, especially, a chiral p x ± ip y state breaking time-reversal symmetry is one of the best candidates for bulk superconducting state of Sr 2 RuO 4 [27][28][29][30][31][32][33][34].…”