Ultrafast all-optical manipulation of the antiferromagnetic order

在过去的一年中，使用建立的实验装置进行了CuB2O4的实验。对这种材料的光致光学和磁动力学进行了广泛的实验研究。特别是，作为激光强度和偏振的函数进行测量，以及外部施加的磁场的影响进行了研究。研究的主要目标是建立激光脉冲诱导的光学和自旋动力学，因为在所选择的特定实验条件下，样品可能经历了激光诱导的相变。更具体地说：在照射之前，样品处于非磁电相。相图和吸收光谱表明，在近红外波段的光激发可以产生磁电效应。跟踪CuB_2O_4中特有的磁电效应的光学指纹，对这一现象进行了研究。我们的实验是成功的，因为它揭示了一个新的现象：在超快的时间尺度（即600 fs）的光激活的CuB2O4的磁电。这一证据得到了证实，作为一个功能的磁场，温度，偏振和强度的泵光束进行了一系列的测量。这种前所未有的固体光学操纵为用电压控制磁体提供了新的可能性，这种电压比磁场更便宜，更容易产生。

In the past year employed the established experimental set-up to perform experiments on CuB2O4. An extensive experimental investigation of the photo-induced optical and magnetic dynamics of this material has been performed. In particular, measurements as a function of the laser intensity and polarization were carried on and the effect of an externally applied magnetic field was investigated as well. The main goal of the investigation was establishing the optical and spin dynamics induced by laser pulses, since under the particular experimental conditions chosen the sample could have undergone a laser-induced phase transition. To be more specific: before illumination the sample was in a non-magnetoelectric phase. However, the phase diagram and the absorption spectrum suggest that the optical excitation in the near-infrared spectral range may induced the magneto-electricity. Tracking the peculiar optical fingerprint of the magneto-electricity in CuB2O4, I studied this phenomenon. Our experiment was successful, since it revealed a novel phenomenon: the magneto-electricity in CuB2O4 was activated by light on the ultrafast time-scale (i.e. 600 fs). This evidence was confirmed by a thorough series of measurements performed as a function of the magnetic field, temperature, polarization and intensity of the pump beam. Such an unprecedented optical manipulation of solids establishes novel possibilities to control magnets with electric voltages, which are much cheaper and easier to generate than magnetic fields.