Defect energetics and magnetic properties of 3d-transition-metal-doped topological crystalline insulator SnTe

Abstract

The introduction of magnetism in SnTe-class topological crystalline insulators is a challenging subject with great importance in the quantum device applications. Based on the first-principles calculations, we have studied the defect energetics and magnetic properties of 3d transition-metal (TM)-doped SnTe. We find that the doped TM atoms prefer to stay in the neutral states and have comparatively high formation energies, suggesting that the uniform TM doping in SnTe with a higher concentration will be difficult unless clustering. In the dilute doping regime, all the magnetic TM atoms are in the high-spin states, indicating that the spin splitting energy of 3d TM is stronger than the crystal splitting energy of the SnTe ligand. Importantly, Mn-doped SnTe has relatively low defect formation energy, largest local magnetic moment, and no defect levels in the bulk gap, suggesting that Mn is a promising magnetic dopant to realize the magnetic order for the theoretically-proposed large-Chern-number quantum anomalous Hall effect (QAHE) in SnTe.

Electronic properties of SnTe-class topological crystalline insulator materials

“…However their doping concentration is very high, and it is likely to damage the TCI phase of SnTe. Another theoretical study comes to a conclusion that the doped TM atoms in SnTe have comparatively high formation energies, and predicts that the uniform TM doping with a higher concentration in SnTe will be difficult unless clustering 69 . To date, the effective magnetic doping in SnTe-class TCI materials is still a challenge, and the further investigations of magnetic effect on TCIs are required.…”

Dopability and Magnetic Properties of 3d Transition Metals in an Atomic-Thick SnTe (001) Monolayer

“…However, the formation energy for the interstitial and adsorbed structure from Fe to Ni is sharply reduced due to the enhanced binding between the TM and SnTe slab, in contrast with the almost unchanged binding for the substitutional case, leaving Ni to another drop in the formation energy for interstitial and adsorbed TM in the SnTe(001) monolayer. Thus, except that the formation energy of Sc, Ti, Mn, and Zn substitution is relatively low as the case for the magnetic doping in SnTe bulk, the formation energy of Ni adsorbed and interstitial in the SnTe(001) monolayer is comparably low, whose probability as a prominent magnetic dopant deserves further evaluation.…”

“…We have calculated the formation energy of the three doping configurations under the same Sn-rich condition as in ref with three sets of Hubbard U corrections, as shown in Figure , and the formation energy is calculated as E normalf [ X ] = E tot [ X ] − E tot [ SnTe ] − prefix∑ n i μ i namely, the energy change between the investigated system ( E tot [ X ]) and the reservoir ( E tot [SnTe], n i μ i ) that is in equilibrium with the defective crystal, where i spans Sn and TM atom. n i indicates the number change of atoms of type i for the doping configuration from the SnTe lattice when the doping occurred.…”

“…The TMs from Ti to Ni show magnetic moments while Cu and Zn do not, and among the magnetic TMs, Mn possesses the largest magnetic moment of 5μ B . The TM ions (Cr–Co) with the number of d electrons between four and seven all show high-spin/weak-field states (4, 5, 4, 3 μ B ), , which could be attributed to the similar bonding even though the symmetry is changed from O h to C 4 v due to the surface bonding cut off. Other than the triply degenerate t 2g and doubly degenerate e g orbitals in the O h crystal field, the d orbitals further split into one doubly degenerate orbital and three nondegenerate orbitals (d xy in t 2g further splits from d xz and d yz , and d x 2 –y 2 and d z 2 in e g split from each other).…”

Plasmons of topological crystalline insulator SnTe with nanostructured patterns

“…Furthermore, the surface states can be modulated by external electric elds and strain effects. 18,[55][56][57] Therefore, compared to the noble metals, high tunability could be accomplished for the plasmons in TCI SnTe nanopatterns, which may open a door to the development of tunable plasmonic nanodevices in topological materials.…”