Polariton drag enabled quantum geometric photocurrents in high-symmetry materials

Ying Xiong, Li-kun Shi, and Justin C. W. Song

Phys. Rev. B 106, 205423 – Published 29 November 2022

Abstract

Lowered symmetry enables access to a wide set of responses not typically accessible in high symmetry materials. Prime examples are time-reversal forbidden quantum geometric photocurrent responses (e.g., linear injection and circular shift photocurrents) that are thought to vanish in nonmagnetic materials. Here we argue that polariton drag processes enable to unblock such quantum geometric photocurrents even in nonmagnetic and centrosymmetric materials. Strikingly, we uncover how a cooperative effect between finite $q$ irradiation and the Fermi surface position leads to a polariton selective photoexcitation (PSP). PSP enables to directly address carriers within tight momentum resolved windows of the Fermi surface to yield giant enhancements of quantum geometric photocurrents. This selectivity enables to directly track momentum resolved quantum geometric quantities along the Fermi surface providing a new tool to interrogate the quantum geometry of high symmetry materials.

Received 15 October 2021
Revised 19 October 2022
Accepted 20 October 2022

DOI:https://doi.org/10.1103/PhysRevB.106.205423

Physics Subject Headings (PhySH)

Light-matter interaction Nanophotonics Nonlinear optics Photovoltaic effect Plasmonics

2-dimensional systems Topological materials

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ying Xiong ¹, Li-kun Shi², and Justin C. W. Song^1,*

¹Division of Physics and Applied Physics, Nanyang Technological University, 637371 Singapore
²Max Planck Institute for the Physics of Complex Systems, Dresden 01187, Germany

^*Corresponding author: justinsong@ntu.edu.sg

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Vol. 106, Iss. 20 — 15 November 2022

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Images

Figure 1
PD charge circular shift photocurrent in BLG displaying resonant like features close to $μ = \pm ℏ ω / 2$ ; these arise from (inset) polariton selective photoexcitation (PSP) wherein carries within a momentum window are excited, see also Figs. 2 and 3. Blue, orange, yellow and purple curves are obtained at temperatures 10 K, 20 K, 50 K, and 100 K. Parameters used: $ℏ ω = 200 meV$ , $| q | = 0.001 {nm}^{- 1}$ corresponding that to free space photons, $| E | = 0.05 V / μ m$ , and $ϕ = π / 2$ . (inset, middle upper panel) Schematic diagram of BLG irradiated by an oblique incidence of light. (inset, middle lower panel) Circular shift current as a function of $ϕ$ for $μ = - 100$ meV. The solid (dashed) lines indicate ${[j_{cir}^{shfit}]}_{x}$ ( ${[j_{cir}^{shfit}]}_{y}$ ).
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Figure 2
PD charge LI photocurrent in BLG. (a) Schematic diagram of a hybrid quantum material/host plasmonic material system, in which the electromagnetic field of the plasmons in the proximal host material (green) induces nonvertical interband transitions and PD photocurrents in the quantum material (yellow). (b) $| q |$ dependence of PD LI photocurrent for Fermi energies $μ = - 100$ meV (blue) and $μ = - 110$ meV (orange). The solid and dashed lines denote temperatures of 10 K and 50 K. The black and blue stars correspond to $| q | = 0.01 {nm}^{- 1}$ (smaller than $q_{c}$ ) and $| q | = 0.03 {nm}^{- 1}$ (i.e., $| q | ≳ q_{c}$ ). (inset) Temperature dependence of the PD LI photocurrent at $| q | = 0.01 {nm}^{- 1}$ for different Fermi energies (color code is the same as in main panel). We have set $| E | = 0.05 V / μ m$ and $ϕ = π / 2$ . (c, d) Schematic illustration of the transition contours (yellow) for $| q | < q_{c}$ (c) and $| q | \sim q_{c}$ (d). The yellow solid (dashed) lines indicate the occupied (unoccupied) section of the transition contour. The black dotted line indicates the Fermi surface. The injection photocurrent can be estimated from the injection rate by accounting for the relaxation or accumulation time, see description in text.
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Figure 3
PD photocurrent as a momentum resolved tool to probe quantum geometry. (a-d) Partial excitation of charge carriers near the Fermi surface in $k$ -space (coloured segment). Here $p_{-} = p - q / 2$ . (e,g) LI photocurrents as a function of $ϕ$ at a fixed magnitude $| q | = 0.03 {nm}^{- 1}$ and $μ = - 110$ meV for $x$ -polarized (e) and $y$ -polarized (g) light in BLG. Here we have used $T = 10$ K and $| E | = 0.05 V / μ m$ . The photocurrents enable to track the corresponding quantum metric dipoles shown in (f) and (h) along the Fermi surface (FS); here we have summed over both $K$ and $K^{'}$ valleys in Eq. (4). We note that for $ϕ = 0$ , the charge carriers close to azimuthal angle $- π$ along the FS are sampled.
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