Quantum Critical Behaviour in Spin and Charge Ordered Systems

几十年来，钛酸锶的量子性质，如其初期的铁电性和在最低温度下保持顺电的倾向，一直令凝聚态物理学家着迷。然而，在这些低温下，钛酸锶和类似的材料在相图上接近向位移铁电相的转变。这种材料为研究通过改变外部参数来调节材料远离这种零温度、量子临界转变的效果提供了很好的机会。流体静压力的应用使钛酸锶远离量子涨落占主导地位的区域，并通过精确的介电测量，允许绘制相图的大区域并观察可能出现的相。以这种方式进行的测量也显示了量子临界性和新的可能的相界的演化的证据。所使用的技术还应该允许研究具有两个或更多耦合序参数的系统中的复杂行为，例如多铁性EuTiO_3。

Quantum properties of SrTiO3, such as its Incipient ferroelectricity and tendency to remain paraelectric down to the lowest temperatures have fascinated condensed matter physicists for several decades. At these low temperatures however SrTiO3 and similar materials lie close to a transition to a displacive ferroelectric phase in their phase diagrams. Such materials offer good opportunities for studying the effects of tuning the material away from this zero-temperature, quantum critical transition by the varying of an external parameter. The application of hydrostatic pressure tunes SrTiO3 away from the region in which quantum fluctuations dominate and, through precise dielectric measurement, allows for a large region of the phase diagram to be mapped and for the observation of possible emergent phases. Measurements taken in this manner have also shown evidence for Quantum Criticality and evolution of a new possible phase boundary. The techniques used should also allow study of complex behaviour in systems with two or more coupled order parameters, such as the multiferroic EuTiO3.