Point-contact spectroscopy of heavy-fermion systems

Naǐdyuk, Yu. G.; Yanson, I. K.

doi:10.1088/0953-8984/10/40/001

Cited by 66 publications

(72 citation statements)

References 104 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Note the calculated curve fits the data well near T c , but deviates around the gap edge with decreasing temperature. Since the contact is ballistic, the local Joule heating effect is ruled out [6,28] as an origin of this deviation. The fitting parameters, ∆ and Γ, are plotted in Fig.…”

mentioning

confidence: 95%

See 1 more Smart Citation

Andreev reflection at the normal-metal/heavy-fermion superconductorCeCoIn5interface

et al. 2005

View full text Add to dashboard Cite

The dynamic conductance of the heavy-fermion superconductor CeCoIn 5 is measured by pointcontact spectroscopy as a function of temperature from 60 K down to 400 mK. The contact between the gold tip and the single-crystal is shown to be in the Sharvin limit with the enhanced sub-gap conductance arising from Andreev reflection. The zero-bias conductance data are best fit using the extended Blonder-Tinkham-Klapwijk model with a d-wave superconducting order parameter. A fit to the full conductance curve at 400 mK indicates strong coupling (2∆(0)/k B T c = 4.6) and quantifies the suppressed Andreev reflection signal, which is a signature of normal-metal/heavy-fermion superconductor junctions. Possibilites for theoretical modeling to account for the suppressed Andreev conductance are suggested.

show abstract

mentioning

confidence: 95%

“…PCS has been widely adopted to investigate the PS of superconductors including HFSs [6,7]. Blonder, Tinkham, and Klapwijk (BTK) formulated a theoretical model for electronic transport across a normal-metal/conventional superconductor (N/S) interface with an arbitrary barrier strength (Z eff ) [8].…”

mentioning

confidence: 99%

Andreev reflection at the normal-metal/heavy-fermion superconductorCeCoIn5interface

et al. 2005

View full text Add to dashboard Cite

show abstract

“…However, a conductance enhancement due to AR has been frequently observed in point-contact junctions with heavy-fermion superconductors [3,4], including our results on CeCoIn 5 [5], albeit reduced [3][4][5]. Deutscher and Nozières addressed this discrepancy by proposing that relevant boundary conditions are without mass enhancement factors [6].…”

mentioning

confidence: 53%

Point-contact Andreev reflection spectroscopy of heavy-fermion-metal/superconductor junctions

Park¹,

Stalzer²,

Sarrao³

et al. 2008

Physica B: Condensed Matter

View full text Add to dashboard Cite

Our previous point-contact Andreev reflection studies of the heavy-fermion superconductor CeCoIn 5 using Au tips have shown two clear features: reduced Andreev signal and asymmetric background conductance. To explore their physical origins, we have extended our measurements to point-contact junctions between single crystalline heavy-fermion metals and superconducting Nb tips. Differential conductance spectra are taken on junctions with three heavy-fermion metals, CeCoIn 5 , CeRhIn 5 , and YbAl 3 , each with different electron mass. In contrast with Au/CeCoIn 5 junctions, Andreev signal is not reduced and no dependence on effective mass is observed. A possible explanation based on a two-fluid picture for heavy fermions is proposed.

show abstract

“…Rourke et al claim that their estimated contact radius satisfies the ballistic criterion [2] at T c and even further at lower temperatures [1]. Our estimation using more rigorous formulas [3,4,5] shows that their contact diameter (d), is larger than the mean free path (l) at T c by a factor of 1.2 -2.3, although l/d ≫ 1 at lower temperatures. Since such an estimation (albeit a convention in the literature) just gives an indirect measure based on bulk parameters, it does not necessarily corroborate that a point contact formed on the surface is ballistic.…”

mentioning

confidence: 64%

Comment on “Spectroscopic Evidence for Multiple Order Parameter Components in the Heavy Fermion SuperconductorCeCoIn5”

Park

Greene

2006

Phys. Rev. Lett.

View full text Add to dashboard Cite

Heavy Fermion Superconductor CeCoIn 5 "Recently, Rourke et al. reported point-contact spectroscopy (PCS) results on the heavy-fermion superconductor CeCoIn 5 [1]. They obtained conductance spectra on the c-axis surfaces of CeCoIn 5 single crystals. Their major claims are two-fold: CeCoIn 5 has i) d-wave pairing symmetry and ii) two coexisting order parameter components. In this Comment, we show that these claims are not warranted by the data presented.First, do their data represent spectroscopic properties of CeCoIn 5 ? Rourke et al. claim that their estimated contact radius satisfies the ballistic criterion [2] at T c and even further at lower temperatures [1]. Our estimation using more rigorous formulas [3,4,5] shows that their contact diameter (d), is larger than the mean free path (l) at T c by a factor of 1.2 -2.3, although l/d ≫ 1 at lower temperatures. Since such an estimation (albeit a convention in the literature) just gives an indirect measure based on bulk parameters, it does not necessarily corroborate that a point contact formed on the surface is ballistic. The actual physical properties at the contact region can be much different from those in bulk, depending on the surface cleanness, roughness, contact pressure, etc. Therefore, whether atypical PCS data such as in Ref.[1] contain intrinsic spectroscopic information or not should be checked more carefully beyond such simple estimations.Second, we point out that the zero-bias conductance peak (ZBCP) and subsequent dip-hump structure seen in Fig. 1(a) of Ref.[1], which is the main feature they attribute to d-wave symmetry, has also been frequently observed in s-wave superconductors [6]. In Fig. 1(a), we show our own data obtained from epitaxial MgB 2 thin films. While other possibilities are open, including multiple contacts, a well-known origin for the dip structure near the gap edge is local heating due to the non-ballistic nature of the contact [6].Third, we have obtained PCS data from CeCoIn 5 single crystals along both (001) and (110) directions over wide temperature ranges [7,8]. These data were taken reproducibly, well within the Sharvin limit, without showing any significant heating effects. They are consistent with each other and can be analyzed with a single order parameter. It is important to sample more than one crystallographic orientations to conclude the order parameter symmetry and if multiple order parameters exist.Finally, Rourke et al. base their claims of the d-wave symmetry on the ZBCP, which they attribute to Andreev bound states (ABS). It is well known that there are several origins for ZBCPs in tunneling conductance measurements [9] and proper diagnostics must be performed to determine if a ZBCP actually arises from ABS, particularly tracking the evolution of the size and shape of the ZBCP with the magnitude and direction of an applied magnetic field [9]. Measurements along different crystallographic orientations would also provide such information [7,8]. Without such diagnostics, the origin of the ZBCP remains unknown. We als...

show abstract

Point-contact spectroscopy of heavy-fermion systems

Cited by 66 publications

References 104 publications

Andreev reflection at the normal-metal/heavy-fermion superconductorCeCoIn5interface

Andreev reflection at the normal-metal/heavy-fermion superconductorCeCoIn5interface

Point-contact Andreev reflection spectroscopy of heavy-fermion-metal/superconductor junctions

Comment on “Spectroscopic Evidence for Multiple Order Parameter Components in the Heavy Fermion SuperconductorCeCoIn5”

Contact Info

Product

Resources

About