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arXiv 1503.00470cond-mat.str-el
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用动力学平均场论研究BiFeO $_3$中压力驱动的金属-绝缘体相变

Pressure-driven metal-insulator transition in BiFeO$_3$ from Dynamical Mean-Field Theory

A. O. Shorikov, A. V. Lukoyanov, V. I. Anisimov, S. Y. Savrasov

摘要:

采用广义梯度修正局域密度近似和动态平均场论相结合的方法研究了BiFeO $_3$在压力作用下的金属-绝缘体相变.我们的顺磁计算被发现是在协议与实验相图:BiFeO 3在环境和高压下的磁性和光谱性质的计算三个实验晶体结构$R3c$,$Pbnm$和$Pm\bar{3}m$。在环境压力下,在$R3c$相,得到的绝缘间隙为1.2 eV,与其实验值吻合得很好。$R3c$和$Pbnm$相都具有与高自旋(HS)到低自旋(LS)转变同时发生的金属-绝缘体转变。$Pbnm$相的临界压力为25-33 GPa,与实验观察结果吻合得很好。高压和高温$Pm\bar{3}m$相表现出实验观察到的金属行为,以及在我们的计算中所考虑的压力的整个范围内,并在33 GPa下经历LS状态,其中实验观察到$Pbnm$到$Pm\bar{3}m$转变。对$Pbnm$结构进行的反铁磁GGA+DMFT计算结果表明,在43 GPa的临界压力下,MIT和HS-LS跃迁同时发生,与实验数据一致.

英文摘要:

A metal-insulator transition (MIT) in BiFeO$_3$ under pressure was investigated by a method combining Generalized Gradient Corrected Local Density Approximation with Dynamical Mean-Field Theory (GGA+DMFT). Our paramagnetic calculations are found to be in agreement with experimental phase diagram: Magnetic and spectral properties of BiFeO3 at ambient and high pressures were calculated for three experimental crystal structures $R3c$, $Pbnm$ and $Pm\bar{3}m$. At ambient pressure in the $R3c$ phase, an insulating gap of 1.2 eV was obtained in good agreement with its experimental value. Both $R3c$ and $Pbnm$ phases have a metal-insulator transition that occurs simultaneously with a high-spin (HS) to low-spin (LS) transition. The critical pressure for the $Pbnm$ phase is 25-33 GPa that agrees well with the experimental observations. The high pressure and temperature $Pm\bar{3}m$ phase exhibits a metallic behavior observed experimentally as well as in our calculations in the whole range of considered pressures and undergoes to the LS state at 33 GPa where a $Pbnm$ to $Pm\bar{3}m$ transition is experimentally observed. The antiferromagnetic GGA+DMFT calculations carried out for the $Pbnm$ structure result in simultaneous MIT and HS-LS transitions at a critical pressure of 43 GPa in agreement with the experimental data.

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