Topological insulator phase in halide perovskite structures

Jin, Hosub; Im, Jino; Freeman, Arthur J

doi:10.1103/physrevb.86.121102

Cited by 126 publications

(130 citation statements)

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“…Here, the first two terms describe the electronic structure of the high symmetric cubic perovskites (12), and the last term, H ISB , breaks the inversion symmetry by ferroelectric polarization. Most importantly, additional orbital mixings between the nearest neighbors emerge in H ISB ; for example, the ISB field along the z direction allows the hopping between the nearest s and p z orbitals, γ z sp , as well as the nearest p x (or p y ) and p z orbitals, γ z pp .…”

Section: Resultsmentioning

confidence: 99%

“…1). This originates from the different band characters in terms of the angular momentum at the valance and conduction band edges common in halide perovskite compounds (12). The angular momentum character of the individual band can be affected by relative energy scales of the crystal field and SOC; the crystal field quenches orbital degrees of freedom, whereas SOC entangles spin and orbital degrees.…”

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confidence: 99%

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Switchable S = 1/2 and J = 1/2 Rashba bands in ferroelectric halide perovskites

Kim

Im²,

Freeman

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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278

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The Rashba effect is spin degeneracy lift originated from spinorbit coupling under inversion symmetry breaking and has been intensively studied for spintronics applications. However, easily implementable methods and corresponding materials for directional controls of Rashba splitting are still lacking. Here, we propose organic-inorganic hybrid metal halide perovskites as 3D Rashba systems driven by bulk ferroelectricity. In these materials, it is shown that the helical direction of the angular momentum texture in the Rashba band can be controlled by external electric fields via ferroelectric switching. Our tight-binding analysis and first-principles calculations indicate that S = 1=2 and J = 1=2 Rashba bands directly coupled to ferroelectric polarization emerge at the valence and conduction band edges, respectively. The coexistence of two contrasting Rashba bands having different compositions of the spin and orbital angular momentum is a distinctive feature of these materials. With recent experimental evidence for the ferroelectric response, the halide perovskites will be, to our knowledge, the first practical realization of the ferroelectric-coupled Rashba effect, suggesting novel applications to spintronic devices.electronic structure | density functional theory | effective Hamiltonian T he Rashba effect has been widely investigated in 2D surfaces, interfaces, quantum wells, and 3D bulk systems (1-6). The essential requisite for the Rashba effect is that the spin degeneracy is lifted by the inversion symmetry-breaking (ISB) field in the presence of the spin-orbit coupling (SOC). To date, major concerns have focused on enlarging Rashba strength characterized by the Rashba coefficient α R (3, 5, 6). The controllability in the direction of the ISB field, on the other hand, has not been seriously considered. In a surface or an interface, the potential gradient generated by the structural inversion asymmetry results in the loss of controllability; the field direction is mainly fixed according to the preformed surface or interface configuration. The situation is similar in recently discovered 3D Rashba material BiTeI (6), because this material has the compositional ISB field between Te and I layers.Controlling the ISB field and ultimately Rashba-type band splitting can be achieved by using a novel ferroelectric Rashba material (7,8). In a ferroelectric system, the bulk polarization controlled by external electric fields generates the ISB field. Therefore, the ferroelectric polarization directly couples to the spin splitting and the helical spin texture in the ferroelectric Rashba material, enabling the helicity reversal via the ferroelectric switching. Recent theoretical study suggested GeTe as a possible candidate for this mechanism, but the direct measurement of the ferroelectric polarization and switching is still missing due to the sizable conductivity of bulk GeTe (7,8).We consider organic-inorganic hybrid metal halide perovskites as promising ferroelectric Rashba materials. The general formula for this materia...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Switchable S = 1/2 and J = 1/2 Rashba bands in ferroelectric halide perovskites

Kim

Im²,

Freeman

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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278

306

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“…However, this pressure range is very small in BiTeI, appearing only at higher orders in k [38], and does not affect the nature of our results presented below. Electronic correlation effects beyond DFT are likely change the transition pressure, but not the presence of a band inversion transition [43].…”

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confidence: 99%

“…We start with a 4-band Dirac model H 0 which has been used to describe topological phase transitions in centrosymmetric systems, such as semiconductor quantum wells [44] and perovskites [43].…”

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Enhancement of the Bulk Photovoltaic Effect in Topological Insulators

Tan

Rappe

2016

Phys. Rev. Lett.

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We investigate the shift current bulk photovoltaic response of materials close to a band inversion topological phase transition. We find that the bulk photocurrent reverses direction across the band inversion transition, and that its magnitude is enhanced in the vicinity of the phase transition. These results are demonstrated with first principles DFT calculations of BiTeI and CsPbI3 under hydrostatic pressure, and explained with an analytical model, suggesting that this phenomenon remains robust across disparate material systems.The field of topological insulators [1,2] has proven to be a fruitful avenue of research in condensed matter physics in recent years. The symmetry protected surface states of topological insulators [3][4][5] give rise to novel and useful phenomena such as dissipationless transport [6,7]. Even though band topology is a ground state property, defined on the occupied valence bands of an insulator [8], the excited state properties should be affected by topological considerations as well. There is a growing body of research investigating the optical properties of topological insulators[9] using photoemission spectroscopy [3,4], Raman spectroscopy [10][11][12][13], nonlinear optics [14][15][16][17][18][19], and photocurrent generation [20][21][22].While the presence or absence of topological surface states has thus far being the main experimental route for detecting topological phase transitions, in this work we propose an optical, non-surface approach for detecting topological phase transitions in the bulk. This is a direct approach which does not rely on the quality or ease of detection of surface states. We consider the influence of band topology on the bulk photovoltaic effect (BPVE, also known as the photogalvanic effect) [23,24], which is the generation of photocurrents in the bulk of a singlephase material.The bulk photovoltaic effect is a second-order optical effect which gives current densities, J r = σ rst E s E t , as a quadratic function of the applied electric fields. This dictates that the BPVE can only be observed in materials with broken inversion symmetry. Measurements of appreciable BPVE have been reported for many ferroelectric materials [25][26][27][28]. In the prototypical ferroelectric BaTiO 3 , experiments [29,30] and first-principles calculations [31] show that the primary mechanism for BPVE is the shift current [32]. In this mechanism, carriers are excited into a current-carrying superposition of excited states. Due to its dominant effect in the bulk photovoltaic response, we will focus on the shift current in this paper.Because optical excitations probe both the valence and conduction band wavefunctions, we expect the band inversion process, which is the interchange of the conduction and valence band characters, to result in dramatic changes in the finite-frequency response functions of the system. We show that band inversion reverses the direction of the shift current. The magnitude of the shift cur- rent is enhanced in the vicinity of the band inversion transition....

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“…2,3 Many studies have ensued with the aim of both improving the performance of these materials in photovoltaic cells and of understanding which physical parameters may determine the efficiencies. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] For example, Lee et al 16 report a solution-processable solar cell which uses a perovskite of mixed halide form, namely methylammonium lead iodide chloride, CH 3 NH 3 PbI 2 Cl (abbreviated as MAPbI 2 Cl), with a solar-to-electrical power conversion efficiency of 10.9%.…”

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confidence: 99%

Modeling of Lead Halide Perovskites for Photovoltaic Applications

2014

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We report first-principles calculations, using the full potential linear augmented plane wave method, on six lead halide semiconductors, namely, CH 3 NH 3 PbI 3 , CH 3 NH 3 PbBr 3 , CsPbX 3 (X=Cl, Br, I), and RbPbI 3 . Exchange is modeled using the modified Becke-Johnson potential. With an appropriate choice of the parameter that defines this potential, an excellent agreement is obtained between calculated and experimental band gaps of the six compounds. We comment on the possibility that the cubic phase of CsPbI 3 , under hydrostatic pressure, could be a topological insulator.

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Topological insulator phase in halide perovskite structures

Cited by 126 publications

References 30 publications

Switchable S = 1/2 and J = 1/2 Rashba bands in ferroelectric halide perovskites

Switchable S = 1/2 and J = 1/2 Rashba bands in ferroelectric halide perovskites

Enhancement of the Bulk Photovoltaic Effect in Topological Insulators

Modeling of Lead Halide Perovskites for Photovoltaic Applications

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