Signatures for spinons in the quantum spin liquid candidate ${\mathrm{Ca}}_{10}{\mathrm{Cr}}_7{\mathrm{O}}_{28}$

Journal Article · 25 November 2019 · Physical Review B

DOI: https://doi.org/10.1103/PhysRevB.100.174428 · OSTI ID:1607143

Sonnenschein, Jonas ^[1]; Balz, Christian  ^[2]; Tutsch, Ulrich ^[3]; Lang, Michael ^[3]; Ryll, Hanjo ^[4]; Rodriguez-Rivera, Jose A. ^[5]; Islam, A. T. M. Nazmul ^[4]; Lake, Bella ^[6]; Reuther, Johannes ^[1]

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1. Freie Univ., Berlin (Germany); Helmholtz-Zentrum Berlin (HZB), (Germany). German Research Centre for Materials and Energy
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. Goethe Univ., Frankfurt (Germany)
4. Helmholtz-Zentrum Berlin (HZB), (Germany). German Research Centre for Materials and Energy
5. National Inst. of Standards and Technology (NIST), Boulder, CO (United States); Univ. of Maryland, College Park, MD (United States)
6. Helmholtz-Zentrum Berlin (HZB), (Germany). German Research Centre for Materials and Energy; Technische Univ. Berlin (Germany)

We present new experimental low-temperature heat capacity and detailed dynamical spin-structure factor data for the quantum spin-liquid candidate material ${\mathrm{Ca}}_{10}{\mathrm{Cr}}_7{\mathrm{O}}_{28}$. The measured heat capacity shows an almost-perfect linear temperature dependence in the range $0.1K ≲T≲ 0.5K$, reminiscent of fermionic spinon degrees of freedom. The spin-structure factor exhibits two energy regimes of strong signal which display rather different but solely diffuse scattering features. We theoretically describe these findings by an effective spinon-hopping model which crucially relies on the existence of strong ferromagnetically coupled triangles in the system. Our spinon theory is shown to naturally reproduce the overall weight distribution of the measured spin-structure factor. Particularly, we argue that various different observed characteristic properties of the spin-structure factor and the heat capacity consistently indicate the existence of a spinon Fermi surface. A closer analysis of the heat capacity at the lowest accessible temperatures hints toward the presence of weak f-wave spinon-pairing terms inducing a small partial gap along the Fermi surface (except for discrete nodal Dirac points) and suggesting an overall Z2 quantum spin-liquid scenario for ${\mathrm{Ca}}_{10}{\mathrm{Cr}}_7{\mathrm{O}}_{28}$.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1607143
• Journal Information: Physical Review B, Vol. 100, Issue 17; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English