Berman Oleg L, Gumbs Godfrey, Martins Gabriel P, Fekete Paula
Physics Department, New York City College of Technology, City University of New York, New York, NY 11201, USA.
The Graduate School and University Center, City University of New York, New York, NY 10016, USA.
Nanomaterials (Basel). 2022 Apr 22;12(9):1437. doi: 10.3390/nano12091437.
We predict Bose-Einstein condensation and superfluidity of dipolar excitons, formed by electron-hole pairs in spatially separated gapped hexagonal α-T3 (GHAT3) layers. In the α-T3 model, the AB-honeycomb lattice structure is supplemented with C atoms located at the centers of the hexagons in the lattice. We considered the α-T3 model in the presence of a mass term which opens a gap in the energy-dispersive spectrum. The gap opening mass term, caused by a weak magnetic field, plays the role of Zeeman splitting at low magnetic fields for this pseudospin-1 system. The band structure of GHAT3 monolayers leads to the formation of two distinct types of excitons in the GHAT3 double layer. We consider two types of dipolar excitons in double-layer GHAT3: (a) "A excitons", which are bound states of electrons in the conduction band (CB) and holes in the intermediate band (IB), and (b) "B excitons", which are bound states of electrons in the CB and holes in the valence band (VB). The binding energy of A and B dipolar excitons is calculated. For a two-component weakly interacting Bose gas of dipolar excitons in a GHAT3 double layer, we obtain the energy dispersion of collective excitations, the sound velocity, the superfluid density, and the mean-field critical temperature Tc for superfluidity.
我们预测了由空间分离的带隙六角形α-T3（GHAT3）层中的电子-空穴对形成的偶极激子的玻色-爱因斯坦凝聚和超流性。在α-T3模型中，AB蜂窝晶格结构由位于晶格六边形中心的C原子补充。我们考虑了在存在质量项的情况下的α-T3模型，该质量项在能量色散谱中打开了一个能隙。由弱磁场引起的能隙打开质量项，在低磁场下对这个赝自旋-1系统起到了塞曼分裂的作用。GHAT3单层的能带结构导致在GHAT3双层中形成两种不同类型的激子。我们考虑双层GHAT3中的两种偶极激子：（a）“A激子”，它是导带（CB）中的电子与中间带（IB）中的空穴的束缚态；（b）“B激子”，它是CB中的电子与价带（VB）中的空穴的束缚态。计算了A和B偶极激子的结合能。对于GHAT3双层中由偶极激子组成的两组分弱相互作用玻色气体，我们得到了集体激发的能量色散、声速、超流密度以及超流性的平均场临界温度Tc。
