Abstract
We present a $^{35}$Cl NMR study for spin $S=1/2$ perfect kagome antiferromagnet Ca-kapellasite (CaCu$_{3}$(OH)$_{6}$Cl$_{2}\cdot$0.6H$_{2}$O) with a magnetic transition at $T^{\ast}=7.2$ K. The static magnetic structure in the ground state has been determined to be a chirality-ordered $Q=0$ state, which is selected by a finite Dzyaloshinskii-Moriya interaction. The low-energy magnetic excitations in the ordered state are investigated by the nuclear spin-lattice relaxation rate measurement. We detect a weakly temperature dependent contribution in the magnetic fluctuations perpendicular to the kagome plane in addition to the dispersive spin-wave contribution in the kagome plane. The low-energy magnetic excitations from the coplanar spin structure are attributed to the zero mode originating from the flat band in this kagome antiferromagnet.
Highlights
INTRODUCTIONDispersive magnon excitations were observed as the T 2 term in the heat capacity and the T 3 term in 1/T1
The ground state of quantum magnets with spin S = 1/2 has been intensively discussed because the quantum fluctuations destabilize the canonical magnetic ordering and give rise to a new state of matter known as a spin-liquid state [1]
From the NMR spectra and 1/T1 measurements in a field applied parallel (H||) and perpendicular (H⊥) to the kagome plane, we found that the ordered state is highly anisotropic due to the coplanar magnetic structure
Summary
Dispersive magnon excitations were observed as the T 2 term in the heat capacity and the T 3 term in 1/T1 In addition to these magnon contributions, Ca-kapellasite has nontrivial magnetic excitations which introduce a T -linear temperature dependence both in the heat capacity and 1/T1. As this temperature dependence is reminiscent of a Fermi-liquid state in conductors, one would invoke a fermionic nature for the low-energy excitations. From the NMR spectra and 1/T1 measurements in a field applied parallel (H||) and perpendicular (H⊥) to the kagome plane, we found that the ordered state is highly anisotropic due to the coplanar magnetic structure. Equivalent Cl sites are located above and below the Cu triangles
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
