ABOUT US
The main research directions of the laboratory:
1, high-temperature superconducting copper oxide and novel iron-based superconducting electrical transmission physical mechanism:
In April 1986, two European scientists, J.G. Bednorz and K.A. Muller, pioneered a new era of superconducting materials. They found that La-Ba-Cu oxide superconductors have a superconducting temperature Tc of over 30K. This result was confirmed by other researchers, since the world set off a wave of discovery of new superconducting materials.
Including the 1987 Zhu Jingwu and others found a breakthrough oxide superconductor: Tc up to 92K of YBa2Cu3O7-X, which is the first time found to work in the liquid nitrogen superconducting materials and so on. Bednorz and Muller both won the 1987 Nobel Prize in Physics. However, the superconducting physical mechanism of HTS Cu oxide is still unknown.
In early 2008, LaFeAsO1-xFx, a novel superconducting material based on Fe-As surface, was found to have a superconducting transition temperature of up to 26 K. This discovery was also found in the field of superconductivity because of the physical nature of superconductivity and ferromagnetism A wave of craze - the study of iron-based superconducting materials, these new superconducting phenomena provide a new opportunity to explore the superconducting mechanism. The new iron-based superconducting materials and high-temperature superconducting copper oxide have some common features, but also have differences. For example, they all have a layered structure. Superconductivity occurs at the copper-oxygen or iron-arsenic planes. Superconductivity also occurs in the antiferromagnetic or spin density wave Doping), indicating that spin fluctuation of iron atoms (or high temperature superconducting copper atoms) plays an important role in the mechanism of superconductivity.
Current theories focus on the nature of quantum magnetic fluctuations under the framework of quantum criticality and form a well-known quantum critical point (QCP) phase diagram. One of the more singular phenomena is the existence of a "pseudogap" in the underdoped region, and its origin and the relationship with superconductivity has been an important core for the study of HTS mechanisms At present, we are also examining the Fermi-liquid state-Non-Fermi-liquid state transition due to the pseudo-bandgap in the phase diagram with MR / Hall transmission characteristics.
2, superconducting / magnetic components and systems:
Superconducting Quantum Interference Device (SQUID) is the most sensitive magnetic sensing element that has been put into practical use in the world. It can measure the magnetic field intensity (~ 0.5 Gauss) ~ 1 fento-Tesla), so the application of very small magnetic field measurement is very important.
SQUID has been widely used in a variety of magnetic measurement areas, such as: magnetic material analysis, geological exploration, biological magnetic field measurement, electronic spin measurement, gravity wave measurement ... and so on. In the past, superconductivity had to be demonstrated at very low temperatures. Traditional superconductors mostly rely on liquid helium for cooling. However, the price of liquid helium has become more and more expensive due to the depletion of the global natural stock of helium and the current availability of helium Can not be synthesized by a large number of artificial, the price of helium will certainly be rising day by day. As a result, high-temperature superconducting elements cooled with liquid nitrogen, which is relatively inexpensive, have become very promising and commercially viable.
However, due to the complex composition of high-temperature superconductors and the special crystal structure of ceramics, thin-film technology has to be used to grow high-temperature superconducting thin films on special susceptors of certain crystals before they are fabricated into components, so that high-quality high-temperature superconducting thin films Epitaxy is not easy, so high-temperature superconducting elements are difficult to produce and yield is not high, the laboratory also published in the early years of film growth process and characteristics of the key articles [eg LM Wang et al., "Mixed- State Hall Effects in YBa2Cu3Oy / PrBa2Cu3Oy Superlattices ", Phys. Rev. Lett. 78, 527 (1997), is the first Taiwanese paper to be accepted by PRL as a high temperature superconducting paper. ], So most of the current commercial superconducting products are still mostly made of low temperature superconducting materials. Recently, we designed the YBaCuO dc-SQUID magnetometer with a SrTiO3 twin crystal substrate with an included angle of 22.6 ° on the 1x1 cm ^ 2 substrate in a direct-coupled manner with a voltage modulation amplitude VPP of 13μV Magnetic field noise is about 10 μΦ0 / Hz1 / 2 at 4 KHz (77 K). This element has been applied to a nuclear magnetic resonance system after an additional spiral plane input coil.
In addition, how to replace the traditional induction coil with the highly sensitive SQUID element and apply it to the measurement system of AC magnetic susceptibility of nano-magnetic particles to improve the detection limit of the system and to develop the magnetic reagent immunoassay system is one of the focuses of the present research . Due to the same size and size of nano-magnetic particles and protein molecules, nano-magnetic particles become a carrier that can be used in conjunction with biological protein molecules for the purpose of magnetic reagent immunoassay. Frequency AC magnetic permeability measurement has a large dynamic range, simultaneous measurement of high concentration and low concentration of the sample. Moreover, the biological protein molecules to be detected are bound directly to the nano-magnetic particles by a bioprobe, which has a simpler verification procedure compared with the traditional biomedical detection method. In addition, the biological protein molecule to be tested is not magnetic in nature, does not interfere with the detection signal, and many trace amounts of protein in the blood of the human body can be used as indicators of health status or disease risk. Therefore, if these biological protein molecules can be effectively and quickly identified Trace protein changes, it will help early diagnosis of disease, and achieve the purpose of early treatment.
On the other hand, high temperature superconductors with extremely low surface resistance in the superconducting state and working above 77 K are one of the most valued and mature applications of high temperature superconductors in recent years. We have designed and assembled a dual sputter gun vacuum coating system to grow high quality, large area (~ 4 x 4 cm2) YBa2Cu3Oy (YBCO) films, providing double-sided YBCO films that are designed for high-temperature superconducting filters, The dust chamber photolithographic process technology and the network analyzer microwave characteristics of the measurement system to establish the laboratory in this research ability is more complete, this series of years of research has become the laboratory in the field of high temperature superconducting applications One of the characteristics of the study.
