Heat capacity evidence for proximity to the Kitaev QSL in A$_2$IrO$_3$ ($A =$ Na, Li)

K. Mehlawat; A. Thamizhavel; Yogesh Singh

doi:10.1103/PhysRevB.95.144406

paper

Heat capacity evidence for proximity to the Kitaev QSL in A $_{2}$ IrO $_{3}$ ( $A =$ Na, Li)

arXiv:1702.08331 · doi:10.1103/PhysRevB.95.144406

Abstract

The honeycomb lattice iridates $A_{2}$ IrO $_{3}$ ( $A =$ Na, Li) are candidates for realization of the Kitaev-Heisenberg model although their proximity to Kitaev's quantum Spin-Liquid (QSL) is still debated. We report on heat capacity $C$ and entropy $S_{ma g}$ for $A_{2}$ IrO $_{3}$ ( $A =$ Na, Li) in the temperature range $0.075 K \leq T \leq 155$ ~K\@. We find a well separated two-peak structure for the magnetic heat capacity $C_{ma g}$ for both materials and $S_{ma g}$ for Na $_{2}$ IrO $_{3}$ shows a shoulder between the peaks with a value close to $\frac{1}{2}$ Rln $2$ . These features signal the fractionalization of spins into Majornana Fermions close to Kitaev's QSL [Phys. Rev. B {\bf 92}, 115122 (2015); Phys. Rev. B {\bf 93}, 174425 (2016).]. These results provide the first thermodynamic evidence that $A_{2}$ IrO $_{3}$ are situated close to the Kitaev QSL. Additionally we measure the high temperature $T \leq 1000$ ~K magnetic susceptibility $χ$ and estimate the Weiss temperature $θ$ in the true paramagnetic state. We find $θ \approx - 127$ ~K and $- 105$ ~K, for Na $_{2}$ IrO $_{3}$ and Li $_{2}$ IrO $_{3}$ , respectively.

5 pages, 4 figures

Heat capacity evidence for proximity to the Kitaev QSL in A $_{2}$ IrO $_{3}$ ( $A =$ Na, Li)

Abstract

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Heat capacity evidence for proximity to the Kitaev QSL in A2​IrO3​ (A= Na, Li)

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Heat capacity evidence for proximity to the Kitaev QSL in A $_{2}$ IrO $_{3}$ ( $A =$ Na, Li)