-
Diamond membranes: platform for photonic and opto-mechanical applications
Authors:
Hsin-Hui Huang,
Gediminas Seniutinas,
Haoran Mu,
Nguyen Hoai An Le,
Eulalia Puig Vilardell,
Vijayakumar Anand,
Jitraporn Vongsvivut,
Tomas Katkus,
Meguya Ryu,
Junko Morikawa,
Saulius Juodkazis
Abstract:
Diamond 1 - 10 micrometers thick membranes are platform for photonic, quantum and opto-mechanic devices with applications across UV-IR spectral ranges. IR characterization of diamond gratings in reflection and transmission showed a change of the IR absorbance dichroism between positive and negative when the grating period was 1-2 wavelengths (free space) including inside the region of the intrinsi…
▽ More
Diamond 1 - 10 micrometers thick membranes are platform for photonic, quantum and opto-mechanic devices with applications across UV-IR spectral ranges. IR characterization of diamond gratings in reflection and transmission showed a change of the IR absorbance dichroism between positive and negative when the grating period was 1-2 wavelengths (free space) including inside the region of the intrinsic diamond absorbance. Femtosecond laser cutting of micrometers-wide and mm-long structures are demonstrated by steps of carbonization > 0.4 J/cm2/pulse (1030 nm/200 fs) and oxidation of diamond membranes. Light intensity distribution inside form-birefringent diamond structure was modeled for a scaled-down structure and wavelength to reveal characteristic interference patterns for different polarizations.
△ Less
Submitted 11 May, 2026;
originally announced May 2026.
-
Olivine annealed up to 1500 C: changes traced by polarised IR reflectance and magnetization
Authors:
Daniel Smith,
Donatas Narbutis,
Hsin-Hui Huang,
Philipp Zanon,
Michael Boschen,
Jitraporn Vongsvivut,
Dominique Appadoo,
Soon Hock Ng,
Haoran Mu,
Tomas Katkus,
Nguyen Hoai An Le,
Dan Kapsaskis,
Andy I. R. Herries,
Vijayakumar Anand,
Meguya Ryu,
Junko Morikawa,
Saulius Juodkazis
Abstract:
Spectral analysis at the infrared (IR) spectral range is introduced with assignment of synthetic red-green-blue (RGB) colours defined by adjustable wavelength and bandwidth. The RGB bands were selected at the phase-specific absorbance A or reflectance R bands of olivine and related materials, which can be formed via high temperature annealing (HTA) of natural minerals up to 1500 C. Natural olivine…
▽ More
Spectral analysis at the infrared (IR) spectral range is introduced with assignment of synthetic red-green-blue (RGB) colours defined by adjustable wavelength and bandwidth. The RGB bands were selected at the phase-specific absorbance A or reflectance R bands of olivine and related materials, which can be formed via high temperature annealing (HTA) of natural minerals up to 1500 C. Natural olivines were collected from quarry at volcanic site in Mortlake, Victoria, Australia and spectrally characterised during IR-THz spectroscopy beamtime experiments at Australian Synchrotron. Phase changes in HTA natural olivines were traced by correlation of optical IR 4-polarisation spectroscopy, X-ray energy dispersive spectroscopy and magnetisation. After HTA, olivine samples were magnetized via precipitation of Fe-rich oxides.
△ Less
Submitted 28 March, 2026;
originally announced April 2026.
-
Nanoscale Surface Analysis of High Entropy Alloy
Authors:
Hsin-Hui Huang,
Meguya Ryu,
Yoshiaki Nishijima,
Haoran Mu,
Mohit Kumar,
Nguyen Hoai An Le,
Adrian Cernescu,
Jitraporn Vongsvivut,
Andrew Siao Ming Ang,
Lina Grineviciute,
Challapalli Subrahmanyam,
Junko Morikawa,
Saulius Juodkazis
Abstract:
Nanoscale surface analysis of 1 micrometer thick high entropy alloys (HEAs) was carried out using nano-IR for hyperspectral imaging and single point spectroscopy in the 700-1700 1/cm spectral range. Nano-IR is based on the detection of scattered light from an oscillating metal coated nano-tip in one of the arms of the Fourier transform infrared spectrometer and has a resolution defined by the tip…
▽ More
Nanoscale surface analysis of 1 micrometer thick high entropy alloys (HEAs) was carried out using nano-IR for hyperspectral imaging and single point spectroscopy in the 700-1700 1/cm spectral range. Nano-IR is based on the detection of scattered light from an oscillating metal coated nano-tip in one of the arms of the Fourier transform infrared spectrometer and has a resolution defined by the tip radius of the probe, 20 nm, regardless of the excitation wavelength. HEA CuPdAgPtAu showed an absorption and reflection increase at 900-1100 1/cm band, which is consistent with Drude-Lorenz modeling of permittivity, however, could also signify oxide formation as tested by X-ray photoelectron spectroscopy of CuPdAgPtAu and CrFeCoNiCuMo. Realization of polarization analysis for nano-IR nano-spectroscopy in the plane perpendicular to the sample's surface is discussed and modeled. The currently available modality of surface analysis with the excitation-detection mode of the p-pol. antenna can be extended to full 3D analysis of the orientational dependencies of local absorbance and refractive index.
△ Less
Submitted 27 March, 2026;
originally announced March 2026.
-
High Entropy Alloy under Shock Compression: Optical-Pump X-Ray-Probe
Authors:
Hsin Hui Huang,
Meguya Ryu,
Shuji Kamegaki,
Dominyka Stonyte,
Tadas Malinauskas,
Yoshiaki Nishijima,
Rosalie Hocking,
Nguyen Hoai An Le,
Tomas Katkus,
Haoran Mu,
Soon Hock Ng,
Samuel Pinches,
Andrew S. M. Ang,
Vygantas Mizeikis,
Nadia Zatsepin,
Kohei Miyanishi,
Toshinori Yabuuchi,
Hirotaka Nakamura,
Alexis Amouretti,
Norimasa Ozaki,
Tommaso Vinci,
Arturas Vailionis,
Eugene G. Gamaly,
Damien G. Hicks,
Junko Morikawa
, et al. (1 additional authors not shown)
Abstract:
High entropy alloys (HEAs) are multi-principal-element alloys designed for tailorable mechanical performance and have been attracting significant engineering interest, yet their fundamental behaviour under extreme dynamic conditions, such as shock loading, remains unexplored. Here, we report laser-shock experiments on two different types of 1-micrometers-thick HEA microfilms, CuPdAgPtAu and CrFeCo…
▽ More
High entropy alloys (HEAs) are multi-principal-element alloys designed for tailorable mechanical performance and have been attracting significant engineering interest, yet their fundamental behaviour under extreme dynamic conditions, such as shock loading, remains unexplored. Here, we report laser-shock experiments on two different types of 1-micrometers-thick HEA microfilms, CuPdAgPtAu and CrFeCoNiCuMo, on 25-micrometers-thick black-Kapton ablator driven by a high intensity laser pulse (532 nm, 5 ns, 16 J, 0.5-mm diameter focal spot) and probed by an X-ray free electron laser (XFEL) pulse (12 keV, 7 fs). Time-resolved X-ray diffraction (XRD) shows the formation of a transient phase with a lattice compression up to 5.1% of the CuPdAgPtAu HEA along the (111) plane; this transient compressed phase existed for 0.3 ns. The impedance matching Hugoniot analysis estimated a shock pressure of 55 +/- 6 GPa in the HEA film, while Au- and Fe-based equations of state (EoS) modelling predict 80 GPa (0.8 MBar) at the free HEA surface. The free HEA surface reached maximum velocities of ~ 5 km/s as recorded from in situ monitoring with the velocity interferometry system for any reflector (VISAR) imaging. These initial HEA results show the suitability of HEA sample preparation and XFEL-based XRD characterisation under extreme shock loading, and are promising for experimental determination of the EoS of this emerging class of materials (beamtime proposal No.: 2024A8503 for a 6-hour preliminary experiment).
△ Less
Submitted 22 March, 2026;
originally announced March 2026.
-
Phase Diagram and Crossover Phases of Topologically Ordered Graphene Zigzag Nanoribbons: Role of Localization Effects
Authors:
Hoang Anh Le,
In Hwan Lee,
Young Heon Kim,
S. -R. Eric Yang
Abstract:
We computed the phase diagram of the zigzag graphene nanoribbons as a function of on-site repulsion, doping, and disorder strength. The topologically ordered phase undergoes topological phase transitions into crossover phases, which are new disordered phases with a nonuniversal topological entanglement entropy with significant variance. The topological order is destroyed by competition between loc…
▽ More
We computed the phase diagram of the zigzag graphene nanoribbons as a function of on-site repulsion, doping, and disorder strength. The topologically ordered phase undergoes topological phase transitions into crossover phases, which are new disordered phases with a nonuniversal topological entanglement entropy with significant variance. The topological order is destroyed by competition between localization effects and on-site repulsion. We found that strong on-site repulsion and/or doping weakens the nonlocal correlations between the opposite zigzag edges. In one of the crossover phases, both $\frac{e^-}{2}$ fractional charges and spin-charge separation were absent; however, charge-transfer correlations between the zigzag edges were possible. Another crossover phase contains $\frac{e^-}{2}$ fractional charges, but no charge transfer correlations. In low-doped zigzag ribbons the interplay between electron localization and on-site repulsion contributes to the spatial separation of quasi-degenerate gap-edge states and protects the charge fractionalization against quantum fluctuations. In all these effects, mixed chiral gap-edge states play an important role. The properties of nontopological strongly disordered and strongly repulsive phases are also observed. Each phase of the phase diagram has a different zigzag-edge structure. Additionally, we investigated the tunneling of solitonic fractional charges under an applied voltage between the zigzag edges of undoped topologically ordered zigzag ribbons, and found that it may lead to a zero-bias tunneling anomaly.
△ Less
Submitted 5 April, 2024; v1 submitted 10 July, 2023;
originally announced July 2023.
-
Optical Hall response of bilayer graphene: the manifestation of chiral hybridised states in broken mirror symmetry lattices
Authors:
V. Nam Do,
H. Anh Le,
V. Duy Nguyen,
D. Bercioux
Abstract:
Understanding the mechanisms governing the optical activity of layered-stacked materials is crucial to the design of devices aimed at manipulating light at the nanoscale. Here, we show that both twisted and slid bilayer graphene are chiral systems that can deflect the polarization of linear polarized light. However, only twisted bilayer graphene supports circular dichroism. Our calculation scheme,…
▽ More
Understanding the mechanisms governing the optical activity of layered-stacked materials is crucial to the design of devices aimed at manipulating light at the nanoscale. Here, we show that both twisted and slid bilayer graphene are chiral systems that can deflect the polarization of linear polarized light. However, only twisted bilayer graphene supports circular dichroism. Our calculation scheme, which is based on the time-dependent Schrödinger equation, is particularly efficient for calculating the optical-conductivity tensor. Specifically, it allows us to show the chirality of hybridized states as the handedness-dependent bending of the trajectory of kicked Gaussian wave packets in bilayer lattices. We show that nonzero Hall conductivity is the result of the noncanceling manifestation of hybridized states in chiral lattices. We also demonstrate the continuous dependence of the conductivity tensor on the twist angle and the sliding vector.
△ Less
Submitted 25 November, 2020; v1 submitted 22 September, 2020;
originally announced September 2020.
-
Time-evolution patterns of electrons in twisted bilayer graphene
Authors:
H. Nam Do,
H. Anh Le,
D. Bercioux
Abstract:
We characterise the dynamics of electrons in twisted bilayer graphene by analysing the time-evolution of electron waves in the atomic lattice. We perform simulations based on a kernel polynomial technique using Chebyshev polynomial; this method does not requires any diagonalisation of the system Hamiltonian. Our simulations reveal that the inter-layer electronic coupling induces the exchange of wa…
▽ More
We characterise the dynamics of electrons in twisted bilayer graphene by analysing the time-evolution of electron waves in the atomic lattice. We perform simulations based on a kernel polynomial technique using Chebyshev polynomial; this method does not requires any diagonalisation of the system Hamiltonian. Our simulations reveal that the inter-layer electronic coupling induces the exchange of waves between the two graphene layers. This wave transfer manifests as oscillations of the layer-integrated probability densities as a function of time. For the bilayer case, it also causes a difference in the wavefront dynamics compared to monolayer graphene. The intra-layer spreading of electron waves is irregular and progresses as a two-stage process. The first one characterised by a well-defined wavefront occurs in a short time | a wavefront forms instead during the second stage. The wavefront takes a hexagon-like shape with the vertices developing faster than the edges. Though the detail spreading form of waves depends on initial states, we observe localisation of waves in specific regions of the moiré zone. To characterise the electron dynamics, we also analyse the time auto-correlation functions. We show that these quantities shall exhibit the beating modulation when reducing the interlayer coupling.
△ Less
Submitted 19 April, 2019; v1 submitted 9 January, 2019;
originally announced January 2019.