Charge-Density-Wave-Induced Peak-Dip-Hump Structure and the Multiband Superconductivity in a Kagome Superconductor ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$

Charge-Density-Wave-Induced Peak-Dip-Hump Structure and the Multiband Superconductivity in a Kagome Superconductor ${CsV}_{3} {Sb}_{5}$

Rui Lou, Alexander Fedorov, Qiangwei Yin, Andrii Kuibarov, Zhijun Tu, Chunsheng Gong, Eike F. Schwier, Bernd Büchner, Hechang Lei, and Sergey Borisenko

Phys. Rev. Lett. 128, 036402 – Published 20 January 2022

Abstract

The entanglement of charge density wave (CDW), superconductivity, and topologically nontrivial electronic structure has recently been discovered in the kagome metal $A V_{3} {Sb}_{5}$ ( $A = K$ , Rb, Cs) family. With high-resolution angle-resolved photoemission spectroscopy, we study the electronic properties of CDW and superconductivity in ${CsV}_{3} {Sb}_{5}$ . The spectra around $\bar{K}$ is found to exhibit a peak-dip-hump structure associated with two separate branches of dispersion, demonstrating the isotropic CDW gap opening below $E_{F}$ . The peak-dip-hump line shape is contributed by linearly dispersive Dirac bands in the lower branch and a dispersionless flat band close to $E_{F}$ in the upper branch. The electronic instability via Fermi surface nesting could play a role in determining these CDW-related features. The superconducting gap of $\sim 0.4 meV$ is observed on both the electron band around $\bar{Γ}$ and the flat band around $\bar{K}$ , implying the multiband superconductivity. The finite density of states at $E_{F}$ in the CDW phase is most likely in favor of the emergence of multiband superconductivity, particularly the enhanced density of states associated with the flat band. Our results not only shed light on the controversial origin of the CDW, but also offer insights into the relationship between CDW and superconductivity.

Received 11 June 2021
Revised 23 November 2021
Accepted 23 December 2021

DOI:https://doi.org/10.1103/PhysRevLett.128.036402

Physics Subject Headings (PhySH)

Charge density waves Electronic structure Nesting

Kagome lattice

Angle-resolved photoemission spectroscopy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Rui Lou ^1,2,3,*, Alexander Fedorov^2,3,†, Qiangwei Yin⁴, Andrii Kuibarov², Zhijun Tu⁴, Chunsheng Gong⁴, Eike F. Schwier ^5,6, Bernd Büchner^2,7, Hechang Lei^4,‡, and Sergey Borisenko^2,§

¹School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China
²Leibniz Institute for Solid State and Materials Research, IFW Dresden, 01069 Dresden, Germany
³Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, 12489 Berlin, Germany
⁴Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
⁵Experimentelle Physik VII, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
⁶Würzburg-Dresden Cluster of Excellence ct.qmat, Germany
⁷Institute for Solid State and Materials Physics, TU Dresden, 01062 Dresden, Germany

^*Corresponding author. lourui@lzu.edu.cn
^†Corresponding author. a.fedorov@ifw-dresden.de
^‡Corresponding author. hlei@ruc.edu.cn
^§Corresponding author. s.borisenko@ifw-dresden.de

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 128, Iss. 3 — 21 January 2022

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) Schematic crystal structure of ${CsV}_{3} {Sb}_{5}$ in the pristine phase. (b) Bulk and (001)-projected BZs in the pristine phase. (c) Temperature dependence of the resistivity $ρ_{x x}$ at $μ_{0} H = 0 T$ . (d)–(f) Constant-energy ARPES intensity plots ( $T = 1.4 K$ , $h ν = 95 eV$ ) at energies of 0, $- 0.10$ , and $- 0.42 eV$ , respectively. The red solid lines indicate the pristine BZs. (g),(h) Photoemission intensity plot and corresponding second derivative plot ( $T = 1.4 K$ ) along the $\bar{Γ} − \bar{K} − \bar{M}$ direction taken with 95-eV photons, respectively. The blue dashed lines indicate the linearly dispersive bands around $\bar{K}$ . (i),(j) Same as (g),(h) recorded along the $\bar{Γ} − \bar{M}$ direction.
Reuse & Permissions
Figure 2
(a) ARPES intensity plot ( $T = 1.4 K$ , $h ν = 50 eV$ , sample no. S1) measured along cut no. 1, which is illustrated by the white arrow in the inset. The black dots of $β$ are determined by the EDCs in (b). Inset: Sketches of the $β$ FS around $\bar{K}$ with pristine BZ. (b) EDC plot of (a) over the momentum range of $0.40 < k_{‖} < 0.66 Å^{- 1}$ . (c),(d) Same as (a),(b) recorded along cut no. 2, which is illustrated by the white arrow in the inset of (c). (e) FS mapping of a sample cleaved at 150 K ( $T = 150 K$ , $h ν = 95 eV$ , sample no. S2). (f) ARPES intensity plot ( $T = 150 K$ ) measured along the $\bar{Γ} − \bar{K} − \bar{M}$ direction with 50-eV photons. The image is divided by the Fermi-Dirac distribution function convolved with the instrumental energy resolution. The red dashed lines are guides to the eye for the band dispersions. (g) EDC plot of (f) over the momentum range of $0.40 < k_{‖} < 0.90 Å^{- 1}$ .
Reuse & Permissions
Figure 3
(a),(b) Sketches of the experimental FSs (solid curves) above and below $T_{CDW}$ together with the folded ones (dashed curves) by the $2 \times 2$ CDW vector, respectively. The inset of (b) illustrates the reconstructed FSs in CDW BZs. The cyan triangles are bolded to indicate the nature of double- $k_{F}$ crossings of flat bands. (c)–(e) Band structure cartoon along the $\bar{Γ} − \bar{K}$ direction above [(c),(d)] and below [(e)] $T_{CDW}$ , respectively. The $α^{*}$ , $κ^{*}$ , and $γ^{*}$ bands represent the original band structure in pristine phase, and the $α^{'}$ , $κ^{'}$ , and $γ^{'}$ bands are the corresponding folded band structure with respect to the momentum cut, where the vertical dashed line locates in (d), connecting adjacent $\bar{M}$ points.
Reuse & Permissions
Figure 4
(a),(c) Temperature dependent EDCs taken at $k_{F}$ ’s of the $η$ and $β$ bands along the $\bar{Γ} − \bar{K}$ and $\bar{Γ} − \bar{K} − \bar{M}$ directions (pristine BZ), where the sample is warmed up from 1.5 and 1.3 K to 8 K, respectively. (b),(d) Same as (a),(c) by cooling down the sample from 8 K to 1.4 and 1.3 K, respectively.
Reuse & Permissions

Physical Review Letters

Charge-Density-Wave-Induced Peak-Dip-Hump Structure and the Multiband Superconductivity in a Kagome Superconductor CsV3Sb5

Rui Lou, Alexander Fedorov, Qiangwei Yin, Andrii Kuibarov, Zhijun Tu, Chunsheng Gong, Eike F. Schwier, Bernd Büchner, Hechang Lei, and Sergey Borisenko

Phys. Rev. Lett. 128, 036402 – Published 20 January 2022

Abstract

Physics Subject Headings (PhySH)

Authors & Affiliations

Article Text (Subscription Required)

Supplemental Material (Subscription Required)

References (Subscription Required)

Issue

Access Options

Authorization Required

Other Options

Download & Share

Images

Figure 1

Figure 2

Figure 3

Figure 4

Log In

Search

Article Lookup

Paste a citation or DOI

Enter a citation

Charge-Density-Wave-Induced Peak-Dip-Hump Structure and the Multiband Superconductivity in a Kagome Superconductor ${CsV}_{3} {Sb}_{5}$