Design principles for shift current photovoltaics

Cook, A.; Fregoso, Benjamin M.; Juan, Fernando de; Coh, Sinisa; Moore, Joel E.

doi:10.1038/ncomms14176

Cited by 299 publications

(304 citation statements)

References 79 publications

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“…The generic results presented here call to investigate the properties recently predicted on crystalline samples (valleytronics, shift-current photovoltaics, and piezoelectronics) [15][16][17][18] as 2D disorder sets in; something that will be pursued in forthcoming work. Having T c = 510 K, GeS monolayers appear as the proper crystalline material platform -already available in the bulk form-for the pursuit of MM-based applications that require crystallinity of the 2D lattice at room temperature.…”

Section: Resultsmentioning

confidence: 99%

Two-Dimensional Disorder in Black Phosphorus and Monochalcogenide Monolayers

et al. 2016

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Ridged, orthorhombic two-dimensional atomic crystals with a bulk Pnma structure such as black phosphorus and monochalcogenide monolayers are an exciting and novel material platform for a host of applications. Key to their crystallinity, monolayers of these materials have a four-fold degenerate structural ground state, and a single energy scale E C (representing the * To whom correspondence should be addressed † Department of Physics. elastic energy required to switch the longer lattice vector along the x− or y−direction) determines how disordered these monolayers are at finite temperature. Disorder arises when nearest neighboring atoms become gently reassigned as the system is thermally excited beyond a critical temperature T c that is proportional to E C /k B . E C is tunable by chemical composition and it leads to a classification of these materials into two categories: (i) Those for which E C ≥ k B T m , and (ii) those having k B T m > E C ≥ 0, where T m is a given material's melting temperature. Black phosphorus and SiS monolayers belong to category (i): these materials do not display an intermediate order-disorder transition and melt directly. All other monochalcogenide monolayers with E C > 0 belonging to class (ii) will undergo a two-dimensional transition prior to melting. E C /k B is slightly larger than room temperature for GeS and GeSe, and smaller than 300 K for SnS and SnSe monolayers, so that these materials transition near room temperature. The onset of this generic atomistic phenomena is captured by a planar Potts model up to the orderdisorder transition. The order-disorder phase transition in two dimensions described here is at the origin of the Cmcm phase being discussed within the context of bulk layered SnSe.

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Section: Resultsmentioning

confidence: 99%

Two-Dimensional Disorder in Black Phosphorus and Monochalcogenide Monolayers

et al. 2016

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“…Likewise, the chirality of both electronic and photonic 23,24 effects in quantum materials can be manipulated: chiral currents and propagating chiral hybrid light-matter modes known as polaritons can benefit from topological protection against backscattering [25][26][27] . Berry phase effects also underlie the phenomenon of 'shift currents'-an optically induced charge separation arising from asymmetry in the electronic wavefunctions-which provides a new paradigm for designing high-performance optical-frequency conversion and photovoltaic materials 28,29 . Recent studies of transition metal monopnictide-based Weyl semimetals (discussed in 'Topological phenomena under control') that exhibit the requisite band topology have revealed giant second-order nonlinear optical responses 30,31 .…”

Section: Nature Materials Doi: 101038/nmat5017mentioning

confidence: 99%

Towards properties on demand in quantum materials

2017

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Q uantum materials are on the ascent. This term embodies a vast portfolio of compounds and phenomena where ramifications of quantum mechanics are demonstrably real. Quantum materials are in the vanguard of contemporary physics in part because these systems afford an exceptional venue to uncover the many roles of symmetry, topology, dimensionality and strong correlations in macroscopic observables. Here we set out to explore the ways and means of creating new states of matter in quantum materials and manipulating their phases via external stimuli. Practical control of these properties is a precondition for exploiting quantum advantages in new photonic, electronic and energy technologies, a task of significant societal impact 1 . We will primarily focus on the following classes of quantum materials: transition metal oxides, Fe-and Cu-based high-T c superconductors, van der Waals semiconductors, topological insulators and Weyl semimetals, and, finally, graphene.The properties of quantum materials are anomalously sensitive to external stimuli. In these systems, interactions associated with spin, charge, lattice and orbital degrees of freedom are commonly on par with the electronic kinetic energy. A rather fragile balance between coexisting and competing ground states can be readily shifted via external stimuli, leading to a raft of quantum phases and transitions between them 2,3 . Furthermore, certain classes of driven quantum states (Fig. 1a and Box 1) are explicit products of coherent interaction between light and matter 4-6 . Alternatively, the properties of quantum materials can be pre-programmed by directly manipulating the electronic wavefunction and the attendant Berry phase that give rise to the anomalous velocity of electrons in a solid [7][8][9] . These complementary avenues of controls mean that investigations no longer need to be reduced to merely observing (in contrast, for example, to astrophysics). Instead, it is now feasible to attain, in a predictable fashion, 'properties on demand' by steering a quantum material towards a desirable ground, metastable or transient state. The past decade has witnessed an explosion in the field of quantum materials, headlined by the predictions and discoveries of novel Landau-symmetry-broken phases in correlated electron systems, topological phases in systems with strong spin-orbit coupling, and ultra-manipulable materials platforms based on two-dimensional van der Waals crystals. Discovering pathways to experimentally realize quantum phases of matter and exert control over their properties is a central goal of modern condensed-matter physics, which holds promise for a new generation of electronic/photonic devices with currently inaccessible and likely unimaginable functionalities. In this Review, we describe emerging strategies for selectively perturbing microscopic interaction parameters, which can be used to transform materials into a desired quantum state. Particular emphasis will be placed on recent successes to tailor electronic interaction parameters through th...

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“…Hence, our results provide the long-sought link between electric polarization and shift current injection. There is numerical evidence that 2D ferroelectric single-layer IV-monochalcogenides have large shift current 22,23 . A recent experiment measuring shift current on thin films of GeS is consistent with our results 27 .…”

Section: Resultsmentioning

confidence: 99%

“…The right-hand-side is gauge invariant and has simple analytical expressions for effective models of monochalcogenides 22,23 . It contains two important physical effects, density of states and the geometry of Bloch wavefunctions.…”

Section: Resultsmentioning

confidence: 99%

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Quantitative relationship between polarization differences and the zone-averaged shift photocurrent

2017

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A relationship is derived between differences in electric polarization between bands and the "shift vector" that controls part of a material's bulk photocurrent, then demonstrated in several models. Electric polarization has a quantized gauge ambiguity and is normally observed at surfaces via the surface charge density, while shift current is a bulk property and is described by shift vector gaugeinvariant at each point in momentum space. They are connected because the same optical transitions that are described in shift currents pick out a relative gauge between valence and conduction bands. We also discuss subtleties arising when there are points at the Brillouin zone where optical transitions are absent. We conclude that two dimensional materials with significant interband polarization differences should have high bulk photocurrent, meaning that the modern theory of polarization can be used as a straightforward way to search for bulk photovoltaic material candidates.

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Design principles for shift current photovoltaics

Cited by 299 publications

References 79 publications

Two-Dimensional Disorder in Black Phosphorus and Monochalcogenide Monolayers

Two-Dimensional Disorder in Black Phosphorus and Monochalcogenide Monolayers

Towards properties on demand in quantum materials

Quantitative relationship between polarization differences and the zone-averaged shift photocurrent

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