Low-Frequency Divergence and Quantum Geometry of the Bulk Photovoltaic Effect in Topological Semimetals

Ahn, Junyeong; Guo, Guang‐Yu; Nagaosa, Naoto

doi:10.1103/physrevx.10.041041

Cited by 179 publications

(239 citation statements)

References 72 publications

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“…In a nonmagnetic solid, the real part of the photoconductivity σ abc gives rise to the photocurrent due to purely linearly polarized light, known as linear shift current, while the imaginary part produces photocurrent due to purely circularly polarized light, known as circular injection current [30,31]. However, in a P T -symmetric magnetic material such as the AF CrI 3 BL, both the linear shift current and circular injection currents would be zero [32]. Instead, there are so-called circular shift current and linear injection current.…”

Section: Theory and Computational Methodsmentioning

confidence: 99%

“…Instead, there are so-called circular shift current and linear injection current. The inject photocurrent conductivity σ abc for a magnetic system is given by [27,32] σ abc = τ η abc where τ is the photoexcited carrier relaxation time and…”

Section: Theory and Computational Methodsmentioning

confidence: 99%

“…2, in the AF BL CrI 3 , because of its P T symmetry, there is no nonvanishing element of usual linear shift photocurrent tensor and circular injection photocurrent which occur in nonmagnetic broken P -symmetry materials [32]. However, there are nonzero elements of circular shift current and linear injection current instead.…”

Section: Shift and Injection Photocurrentsmentioning

confidence: 98%

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Antiferromagnetism-induced second-order nonlinear optical responses of centrosymmetric bilayer CrI3

Gudelli

Guo

2020

Chinese Journal of Physics

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Antiferromagnetism (AF) in AB ′-stacked centrosymmetric bilayer (BL) CrI 3 breaks both spatial inversion (P) and time-reversal (T) symmetries but maintains the combined P T symmetry, thus inducing novel second-order nonlinear optical (NLO) responses such as second-harmonic generation (SHG), linear electric-optic effect (LEO) and bulk photovoltaic effect (BPVE). In this work, we calculate AF-induced NLO responses of the BL CrI 3 based on the density functional theory with the generalized gradient approximation (GGA) plus onsite Coulomb correlation (U), i.e., the GGA+U method. Interestingly, we find that the magnetic SHG, LEO and photocurrent in the AF BL CrI 3 are huge, being comparable or even larger than that of the well-known nonmagnetic noncentrosymmetric semiconductors. For example, the calculated SHG coefficients are in the same order of magnitude as that of MoS 2 monolayer (ML), the most promising 2D material for NLO devices. The calculated LEO coefficients are almost three times larger than that of MoS 2 ML. The calculated NLO photocurrent in the CrI 3 BL is among the largest values predicted so far for the BPVE materials. On the other hand, unlike nonmagnetic semiconductors, the NLO responses in the AF BL CrI 3 are nonreciprocal and also switchable by rotating magnetization direction. Therefore, our interesting findings indicate that the AF BL CrI 3 will not only provide a valuable platform for exploring new physics of low-dimensional magnetism but also have promising applications in magnetic NLO and LEO devices such as frequency conversion, electro-optical switches, and light signal modulators as well as high energy conversion efficiency photovoltaic solar cells.

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Section: Theory and Computational Methodsmentioning

confidence: 99%

Section: Theory and Computational Methodsmentioning

confidence: 99%

Section: Shift and Injection Photocurrentsmentioning

confidence: 98%

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Antiferromagnetism-induced second-order nonlinear optical responses of centrosymmetric bilayer CrI3

Gudelli

Guo

2020

Chinese Journal of Physics

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“…The role of quantum geometry for the LMC in moiré materials such as TBG has not been studied, although connections between quantum geometry and coupling of electrons to electromagnetic fields have been found in other contexts. Following earlier work for first-principles computations of magnetic susceptibilities in insulators [140][141][142], it has been discussed how the quantum geometry of Bloch wave functions affects the orbital magnetic susceptibility [14][15][16], linear [143] and nonlinear optical responses [144][145][146][147], and spin susceptibility of spin-orbit coupled superfluids [148], FIG. 1.…”

Section: Introductionmentioning

confidence: 99%

Light-matter coupling and quantum geometry in moiré materials

et al. 2021

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Quantum geometry has been identified as an important ingredient for the physics of quantum materials and especially of flat-band systems, such as moiré materials. On the other hand, the coupling between light and matter is of key importance across disciplines and especially for Floquet and cavity engineering of solids. Here we present fundamental relations between light-matter coupling and quantum geometry of Bloch wave functions, with a particular focus on flat-band and moiré materials, in which the quenching of the electronic kinetic energy could allow one to reach the limit of strong light-matter coupling more easily than in highly dispersive systems. We show that, despite the fact that flat bands have vanishing band velocities and curvatures, light couples to them via geometric contributions. Specifically, the intraband quantum metric allows diamagnetic coupling inside a flat band; the interband Berry connection governs dipole matrix elements between flat and dispersive bands. We illustrate these effects in two representative model systems: (i) a sawtooth quantum chain with a single flat band and (ii) a tight-binding model for twisted bilayer graphene. For (i) we highlight the importance of quantum geometry by demonstrating a nonvanishing diamagnetic light-matter coupling inside the flat band. For (ii) we explore the twist-angle dependence of various light-matter coupling matrix elements. Furthermore, at the magic angle corresponding to almost flat bands, we show a Floquet-topological gap opening under irradiation with circularly polarized light despite the nearly vanishing Fermi velocity. We discuss how these findings provide fundamental design principles and tools for light-matter-coupling-based control of emergent electronic properties in flat-band and moiré materials.

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“…1c). The concept of anapole order has been employed in nuclear physics 45 , magnetic materials science 44 , strongly correlated electron systems 46,47 , and optoelectronics 48,49 , and it is extended to superconductors by this work. In previous works, the FFLO superconductivity has been proposed in the presence of an external magnetic field [41][42][43]50 or coexistent magnetic multipole order 51,52 .…”

mentioning

confidence: 99%

Anapole superconductivity from $${{{{{{{\mathcal{PT}}}}}}}}$$-symmetric mixed-parity interband pairing

Kanasugi

Yanase

2022

Commun Phys

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Recently, superconductivity with spontaneous time-reversal or parity symmetry breaking is attracting much attention owing to its exotic properties, such as nontrivial topology and nonreciprocal transport. Particularly fascinating phenomena are expected when the time-reversal and parity symmetry are simultaneously broken. This work shows that time-reversal symmetry-breaking mixed-parity superconducting states generally exhibit an unusual asymmetric Bogoliubov spectrum due to nonunitary interband pairing. For generic two-band models, we derive the necessary conditions for the asymmetric Bogoliubov spectrum. We also demonstrate that the asymmetric Bogoliubov quasiparticles lead to the effective anapole moment of the superconducting state, which stabilizes a nonuniform Fulde-Ferrell-Larkin-Ovchinnikov state at zero magnetic fields. The concept of anapole order employed in nuclear physics, magnetic materials science, strongly correlated electron systems, and optoelectronics is extended to superconductors by this work. Our conclusions are relevant for any multiband superconductors with competing even- and odd-parity pairing channels. Especially, we discuss the superconductivity in UTe2.

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Low-Frequency Divergence and Quantum Geometry of the Bulk Photovoltaic Effect in Topological Semimetals

Cited by 179 publications

References 72 publications

Antiferromagnetism-induced second-order nonlinear optical responses of centrosymmetric bilayer CrI3

Antiferromagnetism-induced second-order nonlinear optical responses of centrosymmetric bilayer CrI3

Light-matter coupling and quantum geometry in moiré materials

Anapole superconductivity from $${{{{{{{\mathcal{PT}}}}}}}}$$-symmetric mixed-parity interband pairing

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