Intermediate valence in single crystalline ${\mathrm{Yb}}_{2}{\mathrm{Si}}_{2}\mathrm{Al}$

Intermediate valence in single crystalline ${Yb}_{2} {Si}_{2} Al$

W. J. Gannon, K. Chen, M. Sundermann, F. Strigari, Y. Utsumi, K.-D. Tsuei, J.-P. Rueff, P. Bencok, A. Tanaka, A. Severing, and M. C. Aronson

Phys. Rev. B 98, 075101 – Published 1 August 2018

Abstract

${Yb}_{2} {Si}_{2} Al$ may be a prototype for exploring different aspects of the Shastry-Sutherland lattice, formed by planes of orthogonally coupled Yb ions. Measurements of the magnetic susceptibility find incoherently fluctuating ${Yb}^{3 +}$ moments coexisting with a weakly correlated metallic state that is confirmed by measurements of the electrical resistivity. Increasing signs of Kondo coherence are found with decreasing temperature, including an enhanced Sommerfeld coefficient and Kadowaki-Woods ratio that signal that the metallic state found at the lowest temperatures is a Fermi liquid where correlations have become significantly stronger. A pronounced peak in the electronic and magnetic specific heat indicates that the coupling of the Yb moments to the conduction electrons leads to an effective Kondo temperature that is approximately 30 K. The valence of ${Yb}_{2} {Si}_{2} Al$ has been investigated with electron spectroscopy methods. ${Yb}_{2} {Si}_{2} Al$ is found to be strongly intermediate valent $[v_{F} = 2.68 (2)$ at 80 K]. Taken together, these experimental data are consistent with a scenario where a coherent Kondo lattice forms in ${Yb}_{2} {Si}_{2} Al$ from an incoherently fluctuating ensemble of Yb moments with incomplete Kondo compensation, and strong intermediate valence character.

Received 22 February 2018
Revised 16 May 2018

DOI:https://doi.org/10.1103/PhysRevB.98.075101

Physics Subject Headings (PhySH)

Electronic structure Frustrated magnetism Kondo effect Metals Quantum spin liquid

2-dimensional systems Antiferromagnets Heavy-fermion systems Single crystal materials Strongly correlated systems

Crystal growth DC susceptibility measurements Liquid helium cooling Resistivity measurements Specific heat measurements X-ray techniques

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

W. J. Gannon¹, K. Chen², M. Sundermann^2,3, F. Strigari², Y. Utsumi^3,*, K.-D. Tsuei⁴, J.-P. Rueff^5,6, P. Bencok⁷, A. Tanaka⁸, A. Severing^2,3, and M. C. Aronson¹

¹Texas A&M University, Department of Physics and Astronomy, 4242 TAMU, College Station, Texas 77843, USA
²Institute of Physics II, University of Cologne, Zülpicher Straße 77, D-50937 Cologne, Germany
³Max-Planck-Institute for Chemical Physics of Solids-Nöthnizer Straße 40, 01187 Dresden, Germany
⁴National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30077, Taiwan
⁵Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cédex, France
⁶Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, LCPMR, 75005 Paris, France
⁷Diamond Light Source, Science Division, Didcot OX11 0DE, United Kingdom
⁸Department of Quantum Matter, AdSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan

^*Present address: Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cédex, France.

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 98, Iss. 7 — 15 August 2018

Reuse & Permissions

Access Options

Article Available via CHORUS

Download Accepted Manuscript

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) The temperature dependence of the dc magnetic susceptibility $χ (T) = M / B$ , where the magnetization $M$ is measured in a fixed field $B = 0.1$ T that is oriented along the (001) (blue) and (110) (red) directions. Black lines are fits of the inverse susceptibility $χ^{- 1}$ to the Curie-Weiss law. (b) The temperature dependencies of $χ^{- 1}$ measured with a fixed field $B = 0.1$ T along the (001) (blue) and (110) (red) directions. Black lines are fits of $χ^{- 1}$ to the Curie-Weiss law for $T > 150$ K. (c), (d) The isothermal magnetization $M (H)$ is measured as functions of the magnetic fields $H$ oriented along the (001) direction (c) and (110) direction (d) at different fixed temperatures $T = 1.8$ (red), 5 (black), 20 (blue), 100 (green), and 300 K (gray).
Reuse & Permissions
Figure 2
(a) The total specific heat per ${Yb}_{2} {Si}_{2} Al$ formula unit $C_{p}$ is measured as a function of temperatures between 1.8 $<$ $T$ $<$ 300 K (red circles). A fit to the Debye model with an electronic contribution $γ_{H T} T$ (see text) is shown (green line) along with the Dulong-Petit limit of $3 R$ per mole of each atom, where $R$ is the ideal gas constant (black dashed line). (a) (inset) The excess specific heat per Yb ion $Δ C = C_{p} - C_{p h}$ divided by temperature $Δ C / T$ as a function of temperature. The peak in $Δ C / T$ is fitted to a Schottky expression (black line, see text). (b) The total specific heat divided by temperature $C_{p} / T$ as a function of temperature squared, $T^{2}$ . A fit to the function $C_{p} / T = γ + β T^{2}$ over the range 16 $\leq$ $T$ $\leq$ 35 K is also shown (black line). (c) The excess specific heat per Yb ion divided by temperature $Δ C / T$ as a function of temperature (red circles, left axis) and the excess entropy $S^{mag}$ per Yb ion as a function of temperature (black line, right axis) (see text.) $R \ln 2$ of entropy is marked by the green dashed line on the right axis. The Schottky fit from part (a) inset is also shown (blue line).
Reuse & Permissions
Figure 3
(a) The electrical resistivity $ρ$ as a function of temperature of ${Yb}_{2} {Si}_{2} Al$ , $ρ (T)$ . (b) The electrical resistivity as a function of temperature squared $T^{2}$ is compared to a fit of $ρ (T)$ in the low-temperature region (10 $K \leq T \leq 150$ K) to the Fermi liquid expression $ρ (T$ ) = $ρ_{0}$ + $A T^{2}$ (black line).
Reuse & Permissions
Figure 4
HAXPES data of ${Yb}_{2} {Si}_{2} Al$ measured at 80 and 300 K with $h ν = 6.47$ keV incident photons and a resolution of 250 meV: (a) valence band, (b) Yb $3 d$ core level plus Al $1 s$ , and (c) Si $1 s$ core level. Note, the scale of the Si binding energy has been shifted by 3065 eV. The red arrow marks the plasmon position at 16 eV higher binding energy. (d) Assignment of spectral weights after background correction (black dotted line). The spectral shape of ${Yb}^{3 +}$ has been reproduced with a full multiplet calculation taking into account the plasmon intensities at 16 eV higher binding energies.
Reuse & Permissions
Figure 5
(a) PFY-XAS $L_{α 1}$ data of ${Yb}_{2} {Si}_{2} Al$ for $T = 25$ (blue dots) and 300 K (red dots), and fit to 300-K data (black line), (b) RXES data at $h ν = 8938$ eV incident energy for several temperatures and empirical assignment of spectral weights. Insets: regions of ${Yb}^{2 +}$ and ${Yb}^{3 +}$ peak positions on extended scales. (c) Valence as function of temperature.
Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Intermediate valence in single crystalline ${Yb}_{2} {Si}_{2} Al$

W. J. Gannon, K. Chen, M. Sundermann, F. Strigari, Y. Utsumi, K.-D. Tsuei, J.-P. Rueff, P. Bencok, A. Tanaka, A. Severing, and M. C. Aronson

Phys. Rev. B 98, 075101 – Published 1 August 2018

Abstract

Physics Subject Headings (PhySH)

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Physical Review B

covering condensed matter and materials physics

Intermediate valence in single crystalline Yb2Si2Al

W. J. Gannon, K. Chen, M. Sundermann, F. Strigari, Y. Utsumi, K.-D. Tsuei, J.-P. Rueff, P. Bencok, A. Tanaka, A. Severing, and M. C. Aronson

Phys. Rev. B 98, 075101 – Published 1 August 2018

Abstract

Physics Subject Headings (PhySH)

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

Intermediate valence in single crystalline ${Yb}_{2} {Si}_{2} Al$