Tunable topological states in electron-doped HTT-Pt

Abstract

Driving existing materials to exhibit topologically nontrivial state is of both scientific and technological interests. Using firstprinciple calculations, we propose the first demonstration of electron doping induced multiple quantum phase transition in a single material of the organometallic framework, HTT-Pt, which has been synthesized by reacting triphenylene hexathiol molecules (HTT) with PtCl 2 . At low electron doping, the HTT-Pt converts from a normal insulator to a quantum spin Hall (QSH) insulator with time-reversal symmetry (TRS). At high electron doping, the TRS is further broken making the HTT-Pt a quantum anomalous Hall (QAH) insulator. The topologically nontrivial band gap of the electron-doped HTT-Pt opened by intrinsic spin-orbit coupling (SOC) can be as large as 44.5 meV, which is promising for realizing these quantum phases at high temperatures. The possibility of switching between the QSH and QAH states offers an intriguing platform for new device paradigm by interfacing between a QSH and QAH state. KEYWORDS: Multiple quantum phase transition, electron doping, QSH and QAH insulator, large SOC gaps, QSH/QAH interfaces the semiconductor industry continually shrinks the size of electronic components on silicon chips, the limits of the current technologies are reached due to the smaller size being prevented by the fundamental physical laws. Spintronics, with the advantage of high density and nonvolatility of data storage, the fast data processing, and low-power-consumption, has the potential to revolutionize the electronic devices. Topological insulators (TIs) provide a promising class of spintronics materials because of their exotic dispersive bands and topologically nontrivial electronic states. TIs have a bulk energy gap, which is linked by gapless edge/surface states that facilitate quantized electronic conduction on the boundaries. The edge states in two dimensional (2D) TIs with time-reversal symmetry (TRS), referred to as quantum spin Hall (QSH) states, 1 can host spin-current with different spin orientations propagate in the helical edge states with opposite directions, where spin-orbit coupling (SOC) plays the role analogous to the external magnetic field in quantum Hall systems. QSH states can also give rise to the so-called quantum anomalous Hall (QAH) states 2 when TRS is broken via inducing magnetism, 3, 4 where only one spin orientation propagates in the chiral edge states without need of external magnetic field.The ability to control electronic properties of a material by applying external electric voltage is crucial for spintronics device applications. The electric field allows one to realizing electron or hole doping and, consequently, change the position of Fermi level. A suitable gate dielectric material can offer both low-temperature and low-voltage processability via increasing capacitance. In conventional solid-state field-effect transistors, 5 the electron doping concentration can reach ~10 12 cm -2

Discovery of intrinsic quantum anomalous Hall effect in organic Mn-DCA lattice

“…[28,29] Considering that the half-filled Mn atom has the 3d 5 4s 2 valence-electron configuration, it is expected that the Mn-DCA lattice would be strongly spin-polarized to realize a QAH state, similar to the case of HTT-Pt lattice. [26] Indeed, the All the ab initio calculations are carried out based on projector-augmented wave method [30] with exchange-correlation functional in the Perdew-Berke-Ernzerhof (PBE) form within the generalized-gradient approximation, [31] as implemented in VASP package. [32,33] Fully optimized lattice constant a = 20.66 Å and a strong coordination bond of a Mn-N bond length of 1.94 Å in the force smaller than 0.01 eV/Å are obtained, which are similar to the experimental results on Metal-DCA lattices.…”

First-principles design of a half-filled flat band of the kagome lattice in two-dimensional metal-organic frameworks

“…(Similar 2D MOFs have been fabricated by other groups [8][9][10][11].) Some of these new 2D MOFs have been theoretically proposed to become organic Z 2 topological insulators [12][13][14][15][16][17] or half-metallic ferromagnets [18][19][20][21].…”

“…1(c)]. In the absence of this radical (such as when Z= N), electron or hole doping would be necessary, as described previously [16,36,37]. The structure of trans-Au 3 (THTAP) 2 (trans-Au-THTAP; THTAP = trihydroxytriaminophenalenyl) [39] with M = Au, X = NH, Y = O is shown in Fig.…”

“…Actually, the wave functions forming the kagome bands are not completely localized on Au and spreading over the π -conjugated system, but we can still assume a single-orbital TB model as long as the lattice symmetry is preserved and the parameters of the TB model are somehow renormalized by the effect of spreading. We added a Zeeman term (exchange splitting) to the Hamiltonian considered in [12][13][14]28,46] to include the effect of ferromagnetism [16]. We considered a complex nearest-neighbor (NN) hopping and a real next-nearest-neighbor (NNN) hopping in a Hamiltonian, H = E 0 + H 0 + H SO + H Z , where…”

Layertronic control of topological states in multilayer metal-organic frameworks

“…On the other hand, by keeping iron as the metal and changing the organic ligand to a coronene based molecule, a ferromagnetic semicondutor phase has been found [13]. Currently, a great number of MOFs are predicted to host topological phases [14][15][16][17][18][19][20][21][22]. Within these materials, nickel and palladiumbis(dithiolene) monolayers were experimentally synthesized [23,24], and theoretically shown to host a 2DTI phase for n-doped systems [25].…”