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首页> 外文期刊>Physical review >Short-range Spin And Charge Correlations And Local Density Of States In The Colossal Magnetoresistance Regime Of The Single-orbital Model For Manganites
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Short-range Spin And Charge Correlations And Local Density Of States In The Colossal Magnetoresistance Regime Of The Single-orbital Model For Manganites

机译：锰单轨道模型的巨大磁阻状态下的短程自旋和电荷相关性以及状态的局部密度

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The metal-insulator transition, and the associated magnetic transition, in the colossal magnetoresistance (CMR) regime of the one-orbital model for manganites is studied here using Monte Carlo (MC) techniques in two-dimensional clusters. Both cooperative oxygen lattice distortions and a finite superexchange coupling among the t_(2g) spins are included in our investigations. Charge and spin correlations are studied. In the CMR regime, a strong competition between the ferromagnetic metallic and the antiferromagnetic charge-ordered insulating states is observed. This competition is shown to be important to understand the resistivity peak that appears near the critical temperature. Moreover, it is argued that the system is dynamically inhomogeneous with short-range charge and spin correlations that slowly evolve with MC time, producing the glassy characteristics of the CMR state. The local density of states (LDOS) is also investigated and a pseudogap (PG), identified as a dip in the LDOS at the Fermi energy, is found to exist in the CMR temperature range. The width of the PG in the LDOS is calculated and directly compared to recent scanning-tunneling-spectroscopy (STS) experimental results. The observed agreement between our calculation and the experiment suggests that the depletion of the conductance at low bias observed experimentally is a reflection on the existence of a PG in the LDOS spectra. The apparent homogeneity observed via STS techniques could be caused by the slow time characteristics of this probe. Faster experimental methods should unveil a rather inhomogeneous state in the CMR regime, as already observed in neutron-scattering experiments.
机译：本文在二维簇中使用蒙特卡洛（MC）技术研究了锰矿一轨道模型的巨大磁阻（CMR）态中的金属-绝缘体转变以及相关的磁转变。我们的研究包括t_（2g）自旋之间的合作氧晶格畸变和有限的超交换耦合。研究了电荷和自旋相关性。在CMR体制中，观察到铁磁金属和反铁磁电荷排序的绝缘态之间的激烈竞争。对于了解临界温度附近出现的电阻率峰值，这种竞争非常重要。此外，有人认为该系统在动态上是不均匀的，具有短程电荷和自旋相关性，随着MC时间的发展而缓慢演化，从而产生CMR状态的玻璃状特征。还研究了局部状态密度（LDOS），发现在CMR温度范围内存在伪间隙（PG），该伪间隙（PG）被确定为在费米能量下LDOS的下降。计算LDOS中PG的宽度，并将其与最近的扫描隧道光谱（STS）实验结果直接进行比较。我们的计算与实验之间观察到的一致性表明，实验观察到的低偏置电导的损耗反映了LDOS光谱中PG的存在。通过STS技术观察到的表观均匀性可能是由于该探针的缓慢时间特性所致。如在中子散射实验中已经观察到的那样，更快的实验方法应该揭示出CMR机制中相当不均匀的状态。

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