Crystal structure and Raman-active lattice vibrations of magnetic topological insulators MnBi2Te4·n(Bi2Te3)

Abstract

bly because of the obvious difficulties in the preparation of MnBi 2 Te 4 • n(Bi 2 Te 3 ) with high index n and unavailability of samples.We have succeeded in this regard and present here the crystal structure of the members with n = 4, 5, and 6, summarize all available structural data for MnBi 2 Te 4 • n(Bi 2 Te 3 ), trace the evolution of Raman spectra of MnBi 2 Te 4 • n(Bi 2 Te 3 ) that embraces all n from 0 to 6 as well as n = ∞ (Bi 2 Te 3 ), and provide a thorough analysis of the obtained Raman data. II. SYNTHESIS AND CRYSTAL STRUCTUREOF MnBi 2 Te 4 • n(Bi 2 Te 3 )A. Synthesis and crystal growth

Recent progress in MnBi2nTe3n+1 intrinsic magnetic topological insulators: crystal growth, magnetism and chemical disorder

“…The growth from the melt is done by cooling the stoichiometric melt of the targeted phase through its melting temperature [ 3 , 4 , 13 , 16 , 32 , 35 , 57 , 59 , 60 ]. Modified Bridgman and vertical Bridgman methods were used.…”

“…Single-crystalline blocks of each phase can be isolated from the as-grown ingot. However, due to the intergrowth, especially on the high- n side, sizable pure-phase single crystals with n ≥ 4 have not been obtained even using the vertical Bridgman method, which can achieve more precise and consistent temperature control [ 60 ]. The mixture is typically heated to around 900 ○ C, where they form a homogeneous liquid.…”

“…It requires a larger amount of growth material, but helps to achieve better temperature control in the synthesis. Via this method, despite unavoidable intergrowth for high- n members, one can obtain phases from MnBi 2 Te 4 up to MnBi 14 Te 22 ( n = 7) from the stoichiometric melt [ 60 ]. One can also add MnCl 2 into the growth mixture to provide an Mn-rich environment.…”

Bi2Te3-intercalated MnBi2Te4: ideal candidate to explore intrinsic Chern insulator and high-temperature quantum anomalous Hall effect

“…While the neighboring MBT layers prefer an antiferromagnetic (AFM) while not ferromagnetic (FM) interlayer coupling [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59], leading to that the QAH effect can only be realized in oddlayered MBT and at low temperature (∼1 K) [47]. Latest experiments have shown that layered TI of Bi 2 Te 3 (BT) can be intercalated into MBT by a series of magnetic TIs of MBT•n(BT) [60][61][62][63][64][65][66][67]. Specifically, the FM interlayer coupling has been achieved by increasing BT layers [64][65][66], indicating that intercalating BT layers in MBT may be an efficient way to realize high-temperature QAH effect.…”