标题： 薄镉晶体中振荡幅度可调的索恩德海姆现象 显示英文标题

标题： Scalable amplitude of Sondheimer oscillations in thin cadmium crystals

摘要： 几十年前，桑德海默发现，承载弹道电子的金属晶体的电导率随磁场振荡。 这些以磁场为周期、周期与样品厚度成正比的振荡已在半经典框架下得到理解。 在这里，我们研究了厚度在12.6到475$\mu$米之间的镉单晶中的纵向和横向电导率。当磁场足够大或样品足够厚时，振荡幅度按先前报道的那样呈 $B^{-4}$衰减。 相反，前十个振荡遵循 $B^{-2.5}e^{-B/B_0}$的磁场依赖性，其振幅由电导量子、样品厚度、磁长度和费米面几何形状决定。 这一表达式与半经典情景下的预测不符，后者忽略了朗道量子化。 我们认为，对于费米波矢几乎平行于磁场的状态，经典/量子交叉发生在可及的磁场范围内。 因此，最低朗道管与费米面上由限制效应诱导的扁平环面相交，产生与半经典情况相同的周期振荡。 我们数据的严格理论解释尚不存在。 显示英文摘要

摘要： Decades ago, Sondheimer discovered that the electric conductivity of metallic crystals hosting ballistic electrons oscillates with magnetic field. These oscillations, periodic in magnetic field with the period proportional to the sample thickness, have been understood in a semi-classical framework. Here, we present a study of longitudinal and transverse conductivity in cadmium single crystals with thickness varying between 12.6 to 475 $\mu$m. When the magnetic field is sufficiently large or the sample sufficiently thick, the amplitude of oscillation falls off as $B^{-4}$ as previously reported. In contrast, the ten first oscillations follow a $B^{-2.5}e^{-B/B_0}$ field dependence and their amplitude is set by the quantum of conductance, the sample thickness, the magnetic length and the Fermi surface geometry. This expression is in disagreement with what was predicted in semi-classical scenarios, which neglect Landau quantization. We argue that the classical/quantum crossover occurs at accessible magnetic fields for states whose Fermi wave-vector is almost parallel to the magnetic field. As a consequence, the intersection between the lowest Landau tube and flat toroids on the Fermi surface induced by confinement give rise to oscillations with a periodicity identical to the semi-classical one. A rigorous theoretical account of our data is missing.