Ultrafast all-optical manipulation of the antiferromagnetic order

在过去的一年里，利用建立的实验装置对CuB2O4进行了实验。对该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，测量了激光强度和偏振的函数，并研究了外加磁场的影响。研究的主要目的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，样品可以经历激光诱导的相变。更具体地说：在照明之前，样品处于非磁电相。然而，相图和吸收光谱表明，在近红外光谱范围内的光激发可能会诱发磁电。追踪CuB2O4中磁电的特殊光学指纹，研究了这一现象。我们的实验是成功的，因为它揭示了一个新的现象：CuB2O4中的磁电在超快时间尺度(即600ps)上被光激活。作为抽运光束的磁场、温度、极化和强度的函数进行的一系列彻底的测量证实了这一证据。这种史无前例的固体光学操纵为用电压控制磁铁创造了新的可能性，电压比磁场便宜得多，也更容易产生。

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.