冉绍尔-汤森效应及其电流电压关系

电子流在与气体闸流管中稀有气体作用时,出现经典理论无法解释的冉绍尔-汤森效应,即气体散射截面和电子速度有关.研究了此过程中几何因子、散射概率和总散射截面随电子速度的变化规律,验证了冉绍尔-汤森效应.探究了实验中出现的阴极电流和加速电压偏离二分之三关系的现象,利用排除法确定了可能的原因:经典Drude模型无法较好地描述电子和气体的碰撞.     

Unexpected low thermal conductivity and large power factor in Dirac semimetal Cd_3As_2

Thermoelectrics has long been considered as a promising way of power generation for the next decades. So far,extensive efforts have been devoted to the search of ideal thermoelectric materials, which require both high electrical conductivity and low thermal conductivity. Recently, the emerging Dirac semimetal Cd3As2, a three-dimensional analogue of graphene, has been reported to host ultra-high mobility and good electrical conductivity as metals. Here, we report the observation of unexpected low thermal conductivity in Cd3As2, one order of magnitude lower than the conventional metals or semimetals with a similar electrical conductivity, despite the semimetal band structure and high electron mobility. The power factor also reaches a large value of 1.58 m W·m-1·K-2at room temperature and remains non-saturated up to 400 K.Corroborating with the first-principles calculations, we find that the thermoelectric performance can be well-modulated by the carrier concentration in a wide range. This work demonstrates the Dirac semimetal Cd3As2 as a potential candidate of thermoelectric materials.