外加电场和磁场对外尔半金属能带结构的调控

Manipulation of the Band Structure of Weyl Semimetals by Electric and Magnetic Fields

基于紧束缚近似下的低能有效哈密顿模型,研究了外加电场、外加磁场及同时外加电场和磁场对外尔半金属电子能带结构的调控作用.结果表明,仅在正向(负向)电场作用下,随着电场强度的不断增大,体系的外尔点逐渐向布里渊区边界(布里渊区中心)移动,当电场强度增大到一定程度时,可以实现半金属向半导体或绝缘体的转变;仅在外加磁场作用下,外尔半金属可以形成分立的朗道能级,n=0子带不随着磁长度的增加而变化,n=1和n=2子带随着磁长度的增加不断向费米能级靠近,且相同指标导带和价带间的能隙不断减小;在保持磁长度不变的条件下,体系的外尔点随着外加正向(负向)电场强度的增大逐渐向布里渊区边界(布里渊区中心)移动,在适当的外加电场作用下,n=0子带由部分占据的价带变为第一导带或完全占据的第一价带,实现半金属向半导体或绝缘体的转变.

Based on the low-energy effective hamiltonian model under the tight-binding approximation,the modulation of the electronic band structure of weyl semimetals by applied electric and/or magnetic fields is investigated.The results show that:when only the positive(negative)electric field is applied,the weyl points of system gradually move towards the boundary(center)of the brillouin zone with the increasing of the electric field strength,and when the electric field strength increases to a certain extent,the semimetal-semiconductor(insulator)transition can be relieazed;when only the magnetic field is applied,the weyl semimetal can form the discrete landau levels,the n=0 subband does not change with the increasing of magnetic length while the n≠0 subband gradually approaches the fermi level with the increasing of magnetic length,and the band gap between the conduction and valence bands with same indices gradually decrease;when the magnetic length remains unchanged,the weyl points of system gradually move towards the boundary(center)of the brillouin zone with the increasing of the positive(negative)electric field strength.Under the appropriate electric field,the n=0 subband can change from partially occupied valence band to first conduction band(fully occupied first valence band)and realize the semimetal-semiconductor or semimetal-insulator transitions.