Highly unconventional behavior of the thermodynamic response functions has been experimentally observed in a narrow gap semiconductor samarium hexaboride. Motivated by these observations, we use renormalization group technique to investigate many-body instabilities in the f-orbital narrow gap semiconductors with band inversion in the limit of weak coupling. After projecting out the double occupancy of the f-orbital states, we formulate a low-energy theory describing the interacting particles in two hybridized electron- and hole-like bands. The interactions are assumed to be weak and short-ranged. We take into account the difference between the effective masses of the quasiparticles in each band. Upon carrying out the renormalization group analysis we find that there is only one stable fixed point corresponding to the excitonic instability with time-reversal symmetry breaking for small enough mismatch between the effective masses.
Effects of external pressure on the narrow gap semiconductor Ce$_{3}$Cd$_{2}$As$_{6}$
本文报道了最近发现的Ce $_{3}$ Cd $_{2}$ As $_{6}$的磁性和电子性质。在常压下，Ce $_{3}$ Cd $_{2}$ As $_{6}$呈现半导体性质，激活能隙为74（1）~meV.在136 K时，电阻率的突然增加和比热的峰值与电荷密度波转变相一致。在低温下，$^{3+}$离子的反铁磁有序发生在低于$T_{\rm N} = 4.0$ ~K的位置，其硬磁轴沿$c$ -轴，并具有$Γ_{6} = |\pm1/2\rangle$双重基态.外压的施加强烈地抑制了电荷密度波序，在0.8（1）~GPa以上完全被抑制，并诱导出金属基态。在2~K以上没有发现超导性的证据。相反，反铁磁态受压力的影响，在3.8（1）GPa下达到5.3 K的转变温度。值得注意的是，电阻率异常特征的反铁磁序的变化与压力的增加，表明两个不同的磁相可能存在于Ce $_{3}$ Cd $_{2}$作为$_{6}$压力下。这种顺序变化似乎与$T_{\rm CDW}$和$T_{\rm N}$线交叉有关。
Robust narrow-gap semiconducting behavior in square-net La$_{3}$Cd$_{2}$As$_{6}$
摘要：窄能隙半导体由于其在长波长探测器、热电器件和最近的非平凡拓扑结构方面的潜力而成为抢手的材料。本文报道了一种新型窄禁带半导体材料$R$ $_{3}$ Cd $_{2}$ As $_{6}$（$R=$ La，Ce）的合成和表征。室温下的单晶X-射线衍射结果表明，As正方形网络畸变，Cd空位有序排列在单斜超结构中。La $_{3}$ Cd $_{2}$ As $_{6}$和Ce $_{3}$ Cd $_{2}$ As $_{6}$在279 K和136 K分别出现电荷密度有序态，并伴随着电阻率的显著增加。的La成员的电阻率增加了十三个数量级的冷却，这指向一个非常干净的半导体基态。我们的研究结果表明，在$I4/mmm$母体结构中的轻方网材料是有前途的清洁窄禁带半导体。
