Scanning tunneling microscopy study of superconductivity, magnetic vortices, and possible charge-density wave in ${\mathrm{Ta}}_{4}{\mathrm{Pd}}_{3}{\mathrm{Te}}_{16}$

Scanning tunneling microscopy study of superconductivity, magnetic vortices, and possible charge-density wave in ${Ta}_{4} {Pd}_{3} {Te}_{16}$

Q. Fan, W. H. Zhang, X. Liu, Y. J. Yan, M. Q. Ren, M. Xia, H. Y. Chen, D. F. Xu, Z. R. Ye, W. H. Jiao, G. H. Cao, B. P. Xie, T. Zhang, and D. L. Feng

Phys. Rev. B 91, 104506 – Published 11 March 2015

Abstract

${Ta}_{4} {Pd}_{3} {Te}_{16}$ is a newly discovered layered superconductor with quasi-one-dimensional (1D) structure. Recent thermal transport measurements show the possible existence of nodes in the superconducting gap. Here we report low-temperature scanning tunneling microscopy/spectroscopy study on ${Ta}_{4} {Pd}_{3} {Te}_{16}$ single crystals. We observed stripelike structure composed of atom chains on the cleaved ( $\bar{1} 03)$ surface. There exists charge-density-wave (CDW)-like modulations along stripes with commensurate periods. Meanwhile, the tunneling conductance shows an s-wave-like superconducting gap. The magnetic vortex mapped at low field is highly anisotropic with a bound state in the core. At increased field, strong vortex overlapping is directly observed and the bound state is suppressed, indicating the delocalization of the superconducting quasiparticles. Our observations suggest that ${Ta}_{4} {Pd}_{3} {Te}_{16}$ is of multiband superconductivity with strong 1D characters, which possibly coexist with CDW transition.

Received 24 December 2014
Revised 21 February 2015

DOI:https://doi.org/10.1103/PhysRevB.91.104506

Authors & Affiliations

Q. Fan¹, W. H. Zhang¹, X. Liu¹, Y. J. Yan¹, M. Q. Ren¹, M. Xia¹, H. Y. Chen¹, D. F. Xu¹, Z. R. Ye¹, W. H. Jiao^2,3, G. H. Cao^2,3, B. P. Xie^1,3, T. Zhang^1,3,*, and D. L. Feng^1,3

¹State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China
²Department of Physics, Zhejiang University, Hangzhou 310027, China
³Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, P. R. China

^*tzhang18@fudan.edu.cn

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 91, Iss. 10 — 1 March 2015

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
STM topography of ${Ta}_{4} {Pd}_{3} {Te}_{16}$ and CDW-like modulations. (a) 50 nm $\times$ 50 nm STM image $(V_{bias} = 1.0$ V, $I = 30$ pA). Insert: Crystal structure of ${Ta}_{4} {Pd}_{3} {Te}_{16}$ projected along the [010] directions. (b) Atomically resolved STM image (5 nm $\times$ 5 nm, $V_{bias} = 10$ meV, $I = 50$ pA). (c) STM image showing additional modulations (12 nm $\times$ 12 nm, $V_{bias} = - 100$ meV, $I = 50$ pA). The yellow arrow points to the location where the spectrum in (f) was taken. (d) The Fourier transformation of (c). Lattice Bragg spots are marked by a $^{' *}$ and b $^{' *} .$ Wave vectors of additional modulations are marked by q $_{1}$ , q $_{2}$ , q $_{3} .$ (e) A line profile taken in (a), which shows the surface corrugation. (f) dI/dV spectrum measured at the position shown in (c) at 4 K, within the bias range of $- 200$ meV $\sim 200$ meV.
Reuse & Permissions
Figure 2
The superconducting gap spectrum of ${Ta}_{4} {Pd}_{3} {Te}_{16}$ and its spatial homogeneity. (a) Red spots: Normalized $d I / d V$ spectrum taken at 0.4 K with a modulation of 50 $μ eV .$ Black solid curve: BCS fitting with $Δ = 0.66$ meV and $T_{eff} = 1.2$ K. Blue dashed line: simulated $d$ -wave curve using $Δ = Δ_{0} cos (2 θ)$ with $Δ_{0} = 0.8$ meV and $T_{eff} = 1.2$ K. (Insert: $d I / d V$ spectrum taken on Pb film at 0.4 K, the black solid curve is BCS fitting with $Δ = 1.39$ meV and $T_{eff} = 1.2$ K) (b) A 10 nm $\times$ 10 nm STM image showing the positions for the measured spectra in (c). (c) $d I / d V$ spectra taken on the two points marked in (b). The red curve is shifted up for clarification.
Reuse & Permissions
Figure 3
Magnetic vortex imaging of ${Ta}_{4} {Pd}_{3} {Te}_{16}$ and the vortex core bound states. (a)–(h) Zero bias conductance $(d I / d V)$ mappings measured at 0.4 K at different fields (labeled in the mapping), taken in a same area of 200 nm $\times$ 200 nm. Scale bar is marked in (a). (i) Line profiles of the vortex core in (a), taken along the long axis (blue spots) and short axis (red spots). Solid curves are fittings by using Eq. (1), which yield $ξ_{b^{'}} = 105$ nm, $ξ_{a^{'}} = 36$ nm. Arrows show the FWHMs of the vortex core along long and short axes. (j) $d I / d V$ spectra taken along the dashed line (points 1 to 6) in (a). At the center of the vortex core (on point 6), a zero bias peak is observed (the red curve).
Reuse & Permissions
Figure 4
Field dependence of the superconducting properties. (a) $d I / d V$ spectrum measured in the middle point between two vortices (along the short axis) at various magnetic fields. (b) Left axis (blue curve): the strength of vortex core bound state (defined by $I_{b s} = {ZBC}_{core} - 1)$ that measured at the core center, as a function of field. Right axis (green curve) ZBC values extracted from (a), as a function of field. (c) The FWHMs of the vortex cores measured along long axis (blue spots) and short axis (red spots),as the function of field. The solid curves are calculated from the vortex overlapping model (Ref. [17]).
Reuse & Permissions
Figure 5
Simulated vortex mappings at various field (marked on each image) by using the vortex overlapping model (see text).
Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Scanning tunneling microscopy study of superconductivity, magnetic vortices, and possible charge-density wave in ${Ta}_{4} {Pd}_{3} {Te}_{16}$

Q. Fan, W. H. Zhang, X. Liu, Y. J. Yan, M. Q. Ren, M. Xia, H. Y. Chen, D. F. Xu, Z. R. Ye, W. H. Jiao, G. H. Cao, B. P. Xie, T. Zhang, and D. L. Feng

Phys. Rev. B 91, 104506 – Published 11 March 2015

Abstract

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Physical Review B

covering condensed matter and materials physics

Scanning tunneling microscopy study of superconductivity, magnetic vortices, and possible charge-density wave in Ta4Pd3Te16

Q. Fan, W. H. Zhang, X. Liu, Y. J. Yan, M. Q. Ren, M. Xia, H. Y. Chen, D. F. Xu, Z. R. Ye, W. H. Jiao, G. H. Cao, B. P. Xie, T. Zhang, and D. L. Feng

Phys. Rev. B 91, 104506 – Published 11 March 2015

Abstract

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Authorization Required

Other Options

Download & Share

Images

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Log In

Search

Article Lookup

Paste a citation or DOI

Enter a citation

Scanning tunneling microscopy study of superconductivity, magnetic vortices, and possible charge-density wave in ${Ta}_{4} {Pd}_{3} {Te}_{16}$