2025
[34] Exciton diamagnetic shifts and spin dynamics in lead halide perovskites under high magnetic fields
Chee F. Fong, Thi T. Ha Do, Jung Xing, Sheng Liu, M.A. Prosnikov, Peter C. M. Christianen and A. Granados del Águila*.
[33] Van der Waals photonic integrated circuit with coherent light generation
T. Ren, A. Granados del Águila*, Z. Chen, Q. Xu, X. Zhou, R. Duan, M. Grzeszczyk, X. Gong, K. Watanabe, T. Taniguchi, K.S. Novoselov, M. Koperski & H. Sun.
Nature Communications, 16, 5931 (2025).
Abstract
Two-dimensional semiconductors hold great potential as coherent light sources for photonic integrated circuits. However, the conventional integration of two-dimensional materials onto silicon photonics introduces significant structural and optoelectronic drawbacks, hindering the practical realization of coherent photonic circuits. Here, we introduce the concept of a van der Waals photonic integrated circuit, which is a complete on-chip optical system fabricated entirely from a van der Waals heterostructure. By combining multifunctional two-dimensional materials into a single heterostructure, we realize a fully functional photonic circuitry capable of benchtop coherent light generation, propagation, transmission, and modulation via a silicon back gate. The monolithic approach to heterostructure circuitry supports the effective integration of various photonic components based on two-dimensional materials with stable electro-optic interconnections. The coherence of light emission is systematically verified by second-order correlation experiments at room temperature, showing a clear power-dependent transition to a Poissonian regime. Our work establishes a pathway for coherent van der Waals photonics incorporated with standard silicon manufacturing processes.
2024
[32] Nb impurity-bound excitons as quantum emitters in monolayer WS2
L. Loh, Y. W. Ho, F. Xuan, A. Granados del Águila, Y. Chen, S. Y. Wong, J. Zhang, Z. Wang, K. Watanabe, T. Taniguchi, P. J. Pigram, M. Bosman, S. Y. Quek, M. Koperski and G. Eda
Nature Communications, 15, 10035 (2024).
2023
[31] Ultrafast exciton fluid flow in an atomically thin MoS2 semiconductor
A. Granados del Águila*, Y. R. Wong, I. Wadgaonkar, A. Fieramosca, X. Liu, K. Vaklinova, S. Dal Forno, T. T. H. Do, H. Y. Wei, K. Watanabe, T. Taniguchi, K.S. Novoselov, M. Koperski, M. Battiato and Q. Xiong.
Nature Nanotechnology, 18, 1012 (2023).
Abstract
Excitons (coupled electron–hole pairs) in semiconductors can form collective states that sometimes exhibit spectacular nonlinear properties. Here, we show experimental evidence of a collective state of short-lived excitons in a direct-bandgap, atomically thin MoS2 semiconductor whose propagation resembles that of a classical liquid as suggested by the nearly uniform photoluminescence through the MoS2 monolayer regardless of crystallographic defects and geometric constraints. The exciton fluid flows over ultralong distances (at least 60 μm) at a speed of ~1.8 × 107 m s−1 (~6% the speed of light). The collective phase emerges above a critical laser power, in the absence of free charges and below a critical temperature (usually Tc ≈ 150 K) approaching room temperature in hexagonal-boron-nitride-encapsulated devices. Our theoretical simulations suggest that momentum is conserved and local equilibrium is achieved among excitons; both these features are compatible with a fluid dynamics description of the exciton transport.
Opto-Electronic Advances, 6, 220034(2023).
[30] Electron spin resonance on a 2D van der Waals CrBr3 uniaxial ferromagnet
G. Clemente, M. Moret, A. Granados del Águila, M. Hussain, Z. Sofer, J. Zhou, X. Liu, M. Fanciulli & F. Moro
Journal of Applied Physics, 133, 034301 (2023).
[29] Switching of K-Q intervalley trions fine structure and their dynamics in n-doped monolayer WS2
J. Pei, X. Liu, A. Granados del Águila, D. Bao, S. Liu, M-R. Amara, W. Zhao, F. Zhang, C. You, Y. Zhang, K. Watanabe, T. Taniguchi, H. Zhang & Q. Xiong.
2022
[28] Revealing 2D magnetism in a bulk CrSBr single crystal by electron spin resonance
F. Moro, S. Ke, A. Granados del Águila, A. Söll, Z. Sofer, Q. Wu, M. Yue, L. Li, X. Liu & M. Fanciulli
Advanced Functional Materials, 32, 2207044 (2022).
[27] Room-temperature optically detected magnetic resonance of triplet excitons in a pentacene-doped picene single crystal
F. Moro, M. Moret, A. Ghirri, A. Granados del Águila, Y. Kubozono, L. Beverina & A. Cassinese.
Journal of Materials Research, 37, 1269 (2022).
2021
[26] Direct observation of magnon-phonon strong coupling in two-dimensional antiferromagnet at high magnetic fields
S. Liu, A. Granados del Águila, D. Bhowmick, C. K. Gan, T.T.H. Do, M.A Prosnikov, D. Sedmidubský, Z. Sofer, P.C.M. Christianen, P. Sengupta & Q. Xiong.
Physical Review Letters, 127, 097401 (2021).
[25] Chiral Phonons and Giant Magneto‐Optical Effect in CrBr3 2D Magnet
T. Yin, K. A. Ulman, S. Liu, A. Granados del Águila, Y. Huang, L. Zhang, M. Serra, D. Sedmidubsky, Z. Sofer, S. Y. Quek & Q. Xiong.
Advance Materials, 33, 2101618 (2021).
[24] Light-matter interactions in high quality manganese-doped two-dimensional molybdenum diselenide
S. Liu, Y. Wu, X. Liu, A. Granados del Águila, F. Xuan, A. Chaturvedi, H. Zhang, S. Y. Quek & Q. Xiong.
Science China Materials, 64, 2507 (2021).
2020
[23] Hole and Electron Effective Masses in Single InP Nanowires with a Wurtzite-Zincblende homojunction
D. Tedeschi, H. A. Fonseka, E. Blundo, A. Granados del Águila, Y. Guo, H. H. Tan, P. C. M.
Christianen, C. Jagadish, A.Polimeni and M. De Luca.
ACS Nano, 14, 9, 11613 (2020).
[22] Direct and Indirect Exciton Transitions in Two-dimensional Lead Halide Perovskite Semiconductors
T. Thu Ha Do, A. Granados del Águila*, Jun Xing, Sheng Liu and Qihua Xiong.
The Journal of Chemical Physics 153, 064705 (2020).
[21] Room Temperature Valley Polarization in Atomically-thin Semiconductors via Chalcogenide-Alloying
Sheng Liu, A. Granados del Águila*, Xue Liu, Yihan Zhu, Yu Han, Apoorva Chaturvedi, Pu Gong, Hongyi Yu, Hua Zhang, Wang Yao and Qihua Xiong.
Abstract
Room-temperature manipulation and processing of information encoded in the electronic valley pseudospin and spin degrees of freedoms lie at the heart of the next technological quantum revolution. In atomically thin layers of transition-metal dichalcogenides (TMDs) with hexagonal lattices, valley-polarized excitations and valley quantum coherence can be generated by simply shining with adequately polarized light. In turn, the polarization states of light can induce topological Hall currents in the absence of an external magnetic field, which underlies the fundamental principle of opto-valleytronics devices. However, demonstration of optical generation of valley polarization at room temperature has remained challenging and not well understood. Here, we demonstrate control of strong valley polarization (valley quantum coherence) at room temperature of up to ∼50% (∼20%) by strategically designing Coulomb forces and spin–orbit interactions in atomically thin TMDs via chalcogenide alloying. We show that tailor making the carrier density and the relative order between optically active (bright) and forbidden (dark) states by key variations on the chalcogenide atom ratio allows full control of valley pseudospin dynamics. Our findings set a comprehensive approach for intrinsic and efficient manipulation of valley pseudospin and spin degree of freedom toward realistic opto-valleytronics devices.
[20] Bright Exciton Fine-Structure in Two-Dimensional Lead Halide Perovskites
T. Thu Ha Do, A. Granados del Águila*, Dong Zhang, Jun Xing, Sheng Liu, Mikhail Prosnikov, Weibo Gao, Kai Chang, Peter C.M. Christianen and Qihua Xiong.
Nano Letters 20, 7, 5141 (2020)
Abstract
The fast-growing field of atomically thin semiconductors urges a new understanding of two-dimensional excitons, which entirely determine their optical responses. Here, taking layered lead halide perovskites as an example of unconventional two-dimensional semiconductors, by means of versatile optical spectroscopy measurements, we resolve fine-structure splitting of bright excitons of up to ∼2 meV, which is among the largest values in two-dimensional semiconducting systems. The large fine-structure splitting is attributed to the strong electron–hole exchange interaction in layered perovskites, which is proven by the optical emission in high magnetic fields of up to 30 T. Furthermore, we determine the g-factors for these bright excitons as ∼+1.8. Our findings suggest layered lead halide perovskites are an ideal platform for studying exciton spin-physics in atomically thin semiconductors that will pave the way toward exciton manipulation for novel device applications.
[19] Efficient Up-Conversion Photoluminescence in All-Inorganic Lead Halide Perovskite Nanocrystals
A. Granados del Águila, T. Thu Ha Do, Jun Xing, Wen Jie Jee, Jacob B. Khurgin and Qihua Xiong.
Nano Research 13, 1962 (2020).
[18] van der Waals Epitaxy of Earth-Abundant Zn3P2 on Graphene for Photovoltaics
Rajrupa Paul, Nicolas Humblot, Simon Escobar Steinvall, Elias Zsolt Stutz, Shreyas Sanjay Joglekar, Jean-Baptiste Leran, Mahdi Zamani, Cyril Cayron, Roland Logé, A. Granados del Águila, Qihua Xiong and Anna Fontcuberta i Morral.
Crystal Growth & Design 20, 3816 (2020).
[17] Probing Momentum-indirect Excitons by Near-resonance Photoluminescence Excitation Spectroscopy in WS2 Monolayer
Di Bao, A. Granados del Águila*, T. Thu Ha Do, Sheng Liu, Jiajie Pei and Qihua Xiong.
2D Materials 7, 031002 (2020).
Abstract
Coulomb-bound electron-hole pairs (excitons) dominate the optical response of atomically-thin transition metal dichalcogenides (TMDs) semiconductors. The photoluminescence spectrum in W-based TMDs monolayers (i.e. WS2 and WSe2) at low temperature exhibits much richer features than Mo-based TMDs monolayers, whose origin is currently not well understood. Herein, by using near-resonant photoluminescence excitation spectroscopy, we probe the scattering events between excitons and phonons with large -momentum, which provides strong evidence for the momentum-indirect nature of the optical bandgap in monolayer WS2. The scattering between carriers and zone-edge phonons creates excitons at different valleys, among which, the lowest-energy is momentum-indirect. Our findings highlight that more efforts are required to solve the current debate on the inherent bandgap nature of TMD monolayers and the complex photoluminescence spectrum reported on W-based compounds.
2019
[16] Linearly Polarized Luminescence of Atomically Thin MoS2 Semiconductor Nanocrystals
A. Granados del Águila, Sheng Liu, T. Thu Ha Do, Zhuangchai Lai, Thu Ha Tran, Sean Ryan Krupp, Zhi-Rui Gong, Hua Zhang, Wang Yao and Qihua Xiong.
[15] Manipulating Efficient Light Emission in Two-dimensional Perovskite Crystals by Pressure-induced Anisotropic Deformation
Sheng Liu, Shishuai Sun, Chee Kwan Gan, A. Granados del Águila, Yanan Fang, Jun Xing, T. Thu Ha Do, Timothy J. White, Hongguo Li, Wei Huang and Qihua Xiong.
Science Advances 5, eaav9445 (2019).
[14] Unusual Spin Properties of InP Wurtzite Nanowires revealed by Zeeman Splitting Spectroscopy
D. Tedeschi, M. De Luca, P. E. Faria Junior, A. Granados del Águila, Q. Gao, H. H. Tan, B. Scharf, P. C. M. Christianen, C. Jagadish, J. Fabian and A. Polimeni.
Physical Review B 99, 161204(R) (2019).
2018
[13] Two-Dimensional and Emission-Tunable: An Unusual Perovskite Constructed from Lindqvist-Type [Pb6Br19]7- Nanoclusters
Xinxiong Li, T., Thu Ha Do, A. Granados del Águila, Yinjuan Huang, Wangqiao Chen, Yongxin Li, Rakesh Ganguly, Samuel Morris, Qihua Xiong, Dong-sheng Li and Qichun Zhang.
Inorganic Chemistry 57, 14035 (2018).
[12] A 3D Haloplumbate Framework Constructed From Unprecedented Lindqvist-like
Highly-Coordinated [Pb6Br25]13- Nanoclusters with Temperature-Dependent Emission
Xinxiong Li T., Thu Ha Do, A. Granados del Águila, Yinjuan Huang, Wangqiao Chen, Qihua Xiong and Qichun Zhang.
Chemistry – An Asian Journal, 13, 3185 (2018).
2017
[11] Optical Spectroscopy of Dark and Bright Excitons in CdSe Nanocrystals in High Magnetic Fields
A. Granados del Águila*, G. Pettinari, E. Groeneveld, C. de Mello Donegá, D. Vanmaekelbergh, J. C. Maan and P. C. M. Christianen.
Journal of Physical Chemistry C, 121, 23693-23704 (2017).
[10] Optical Study on Intrinsic Exciton States in High-Quality CH3NH3PbBr3 Single Crystals
T. Thu Ha Do, A. Granados del Águila*, C. Cui, J. Xing, Z. Ning and Q. Xiong
Physical Review B 96, 075308 (2017).
2016
[9] Excitonic Valley Effects in Monolayer WS2 under High Magnetic Fields
G. Plechinger, P. Nagler, A. Arora, A. Granados del Águila, M. V. Ballottin, T. Frank, P. Steinleitner, M. Gmitra, Jaroslav Fabian, P. C. M. Christianen, R. Bratschitsch, C. Schüller and T. Korn
Nano Letters, 16, 7899-7904 (2016).
[8] Magnetic-Field-Induced Rotation of Polarized Light Emission from Monolayer WS2
TR. Schmidt, A. Arora, G. Plechinger, P. Nagler, A. Granados del Águila, M. V. Ballottin, P. C. M Christianen, S. Michaelis de Vasconcellos, C. Schüller, T. Korn and R. Bratschitsch.
Physical Review Letters, 117, 077402 (2016).
[7] Value and Anisotropy of the Electron and Hole Mass in Pure Wurtzite InP Nanowires
D. Tedeschi, M. De Luca, A. Granados del Águila, Q. Gao, G. Ambrosio, M. Capizzi, H. H. Tan, P.C. M. Christianen, C. Jagadish and A. Polimeni.
Nano Letters, 16, 6213-6221 (2016).
[6] Trion Fine Structure and Coupled Spin-Valley Dynamics in Monolayer Tungsten Disulfide
G. Plechinger, P. Nagler, A. Arora, R. Schmidt, A. Chernikov, A. Granados del Águila, P.C.M.
Christianen, R. Bratschitsch, C. Schüller and Tobias Korn.
Nature Communications, 7, 12715 (2016).
[5] Effect of Electron-Hole Overlap and Exchange Interaction on Exciton Radiative Lifetimes of CdTe/CdSe Heteronanocrystals
A. Granados del Águila, E. Groeneveld, J. C. Maan, C. de Mello Donega and P. C. M. Christianen.
ACS Nano 10, 4102-4110 (2016).
2015
[4] Optical Investigation of Monolayer and Bulk Tungsten Diselenide (WSe2) in High
Magnetic Fields
A. A. Mitioglu, P. Plochocka, A. Granados del Águila, P. C. M Christianen, G. Deligeorgis, L. Kulyuk and D. K. Maude.
Nano Letters 15, 4387-4392 (2015).
2014
[3] Observation of the Full Exciton and Phonon Fine Structure in CdSe/CdS Dot-in-Rod Heteronanocrystals
A. Granados del Águila, B. Jha, F. Pietra, E. Groeneveld, C. de Mello Donega, J. C. Maan, D.
Vanmaekelbergh and P. C. M. Christianen.
2013
[2] High Magnetic Field Reveals the Nature of Excitons in a Single GaAs/AlAs Core/Shell Nanowire
P. Plochocka, A.A. Mitioglu, D. K. Maude, G.L.J.A. Rikken, A. Granados del Águila, P.C.M. Christianen, P. Kacman and Hadas Shtrikman.
Nano Letters 13, 2442-2447 (2013).
[1] Optically Excited Multi-band Conduction in LaAlO3/SrTiO3 Heterostructures
V. K. Guduru, A. Granados del Águila, S. Wenderich, M.K. Kruize, A. McCollam, P.C.M. Christianen, U. Zeitler, A. Brinkman, G. Rijnders, H. Hilgenkamp and J. C. Maan.
Andres Granados del Aguila Lab 