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arXiv 1210.4355cond-mat.str-el
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双钙钛矿相Ba3YIr2O9中自旋轨道驱动的自旋液体基态

Possible spin-orbit driven spin-liquid ground state in the double perovskite phase of Ba3YIr2O9

Tusharkanti Dey, A. V. Mahajan, R. Kumar, B. Koteswararao, F. C. Chou, A. A. Omrani, H. M. Ronnow

摘要:

本文报道了在1273 K、8 GPa压力下六方相Ba_3YIr_2O_9向立方相双钙钛矿结构(室温下稳定)的结构转变。虽然环境压力(AP)合成的样品在4K下经历长程磁有序,但高压(HP)合成的样品在2K下不有序,这从我们的磁化率、热容和核磁共振(NMR)测量中得到证明。此外,对于HP样品,我们的热容数据在2- 10 K的温度(T)范围内具有γ *T+ β *T3的形式,Sommerfeld系数γ = 10 mJ/mol·Ir K2。~(89)Y NMR位移在4- 120 K范围内不随温度变化,自旋-晶格弛豫速率在8- 45 K范围内随温度呈线性变化(高于此温度时,自旋-晶格弛豫速率与温度无关)。两个样品的电阻测量证实它们是半导体的。我们的数据提供了证据,形成一个5d为基础的,无隙,量子自旋液体(QSL)的立方(HP)相的Ba 3 YIr 2 O 9。在这幅图中,热容量中的T项和89 Y 1/T1的线性变化来自自旋费米面的激发。我们的研究结果支持了理论上的建议[G.陈河,巴西-地Pereira和L. Balents,Phys.Rev.B82,174440(2010)],强自旋-轨道耦合可以增强量子波动并导致双钙钛矿晶格中的QSL状态。

英文摘要:

We report the structural transformation of hexagonal Ba3YIr2O9 to a cubic double perovskite form (stable in ambient conditions) under an applied pressure of 8GPa at 1273K. While the ambient pressure (AP) synthesized sample undergoes long-range magnetic ordering at 4K, the high pressure(HP) synthesized sample does not order down to 2K as evidenced from our susceptibility, heat capacity and nuclear magnetic resonance (NMR) measurements. Further, for the HP sample, our heat capacity data have the form gamma*T+beta*T3 in the temperature (T) range of 2-10K with the Sommerfeld coefficient gamma=10mJ/mol-Ir K2. The 89Y NMR shift has no T-dependence in the range of 4-120K and its spin-lattice relaxation rate varies linearly with T in the range of 8-45K (above which it is T-independent). Resistance measurements of both the samples confirm that they are semiconducting. Our data provide evidence for the formation of a 5d based, gapless, quantum spin-liquid (QSL) in the cubic (HP) phase of Ba3YIr2O9. In this picture, the T term in the heat capacity and the linear variation of 89Y 1/T1 arises from excitations out of a spinon Fermi surface. Our findings lend credence to the theoretical suggestion [G. Chen, R. Pereira, and L. Balents, Phys. Rev. B 82, 174440 (2010)] that strong spin-orbit coupling can enhance quantum fluctuations and lead to a QSL state in the double perovskite lattice.

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