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446 results on '"Khodaparast, Giti A."'

1. Mineral Detection of Neutrinos and Dark Matter 2024. Proceedings

Author

Baum, Sebastian, Huber, Patrick, Stengel, Patrick, Abe, Natsue, Ang, Daniel G., Apollonio, Lorenzo, Araujo, Gabriela R., Balogh, Levente, Boukhtouchen, Pranshu Bhaumik Yilda, Bramante, Joseph, Caccianiga, Lorenzo, Calabrese-Day, Andrew, Chang, Qing, Collar, Juan I., Ebadi, Reza, Elykov, Alexey, Freese, Katherine, Fung, Audrey, Galelli, Claudio, Gleason, Arianna E., Perez, Mariano Guerrero, Hakenmüller, Janina, Hanyu, Takeshi, Hasebe, Noriko, Hirose, Shigenobu, Horiuchi, Shunsaku, Hoshino, Yasushi, Ido, Yuki, Ivanov, Vsevolod, Kamiyama, Takashi, Kato, Takenori, Kawamura, Yoji, Kelso, Chris, Khodaparast, Giti A., LaVoie-Ingram, Emilie M., Leybourne, Matthew, Liu, Xingxin, Lucas, Thalles, Mariani, Brenden A. Magill Federico M., Mkhonto, Sharlotte, Mumm, Hans Pieter, Murase, Kohta, Naka, Tatsuhiro, Oguni, Kenji, Ream, Kathryn, Scholberg, Kate, Shen, Maximilian, Spitz, Joshua, Suzuki, Katsuhiko, Takla, Alexander, Tang, Jiashen, Tapia-Arellano, Natalia, Vermeesch, Pieter, Vincent, Aaron C., Vladimirov, Nikita, Walsworth, Ronald, Waters, David, Wurtz, Greg, Yamasaki, Seiko, and Zhang, Xianyi

Subjects
Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, High Energy Physics - Experiment, High Energy Physics - Phenomenology, Physics - Instrumentation and Detectors
Abstract

The second "Mineral Detection of Neutrinos and Dark Matter" (MDvDM'24) meeting was held January 8-11, 2024 in Arlington, VA, USA, hosted by Virginia Tech's Center for Neutrino Physics. This document collects contributions from this workshop, providing an overview of activities in the field. MDvDM'24 was the second topical workshop dedicated to the emerging field of mineral detection of neutrinos and dark matter, following a meeting hosted by IFPU in Trieste, Italy in October 2022. Mineral detectors have been proposed for a wide variety of applications, including searching for dark matter, measuring various fluxes of astrophysical neutrinos over gigayear timescales, monitoring nuclear reactors, and nuclear disarmament protocols; both as paleo-detectors using natural minerals that could have recorded the traces of nuclear recoils for timescales as long as a billion years and as detectors recording nuclear recoil events on laboratory timescales using natural or artificial minerals. Contributions to this proceedings discuss the vast physics potential, the progress in experimental studies, and the numerous challenges lying ahead on the path towards mineral detection. These include a better understanding of the formation and annealing of recoil defects in crystals; identifying the best classes of minerals and, for paleo-detectors, understanding their geology; modeling and control of the relevant backgrounds; developing, combining, and scaling up imaging and data analysis techniques; and many others. During the last years, MDvDM has grown rapidly and gained attention. Small-scale experimental efforts focused on establishing various microscopic readout techniques are underway at institutions in North America, Europe and Asia. We are looking ahead to an exciting future full of challenges to overcome, surprises to be encountered, and discoveries lying ahead of us., Comment: Summary and proceedings of the MDvDM'24 conference, Jan 8-11 2024

Published
2024

2. Passive low energy nuclear recoil detection with color centers -- PALEOCCENE

Author

Alfonso, Krystal, Araujo, Gabriela R., Baudis, Laura, Bowden, Nathaniel, Cogswell, Bernadette K., Erickson, Anna, Galloway, Michelle, Hecht, Adam A., Mudiyanselage, Rathsara R. H. Herath, Huber, Patrick, Jovanovic, Igor, Khodaparast, Giti A., Magill, Brenden A., O'Donnell, Thomas, Smith, Nicholas W. G., and Zhang, Xianyi

Subjects
High Energy Physics - Experiment
Abstract

The PALEOCCENE concept offers the potential for room-temperature, passive and robust detectors in the gram to kilogram range for the detection of low-energy nuclear recoil events. Nuclear recoil events can be caused by neutron scattering, coherent elastic neutrino nucleus scattering (CEvNS) or dark matter scattering and therefore, PALEOCCENE could find applications in all three areas. In this white paper we present current and planned R&D efforts to study the feasibility of this technique., Comment: 22 pages, 6 figures, comments welcome. White paper contribution to Snowmass 2021

Published
2022

3. Light-Activated Nuclear Spin Polarization in Dilute Ferromagnetic (Ga,Mn)As

Author

Tokarski III, John T., Bowers, Clifford R, Thapa, Sunil K., Stanton, Christopher J., Liu, Xinyu, Furdyna, Jacek, Magill, Brenden, and Khodaparast, Giti A.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Condensed Matter - Other Condensed Matter
Abstract

We study light-induced nuclear spin-polarization in a thin film of Ga1-xMnxAs (x 0.04), a dilute ferromagnetic semiconductor, grown on a GaAs substrate. High-field inductively-detected Ga-71 NMR was performed with samples immersed in superfluid He to investigate the effects of continuous-wave near band-edge optical illumination on lattice nuclear spins in the ferromagnetic phase. The photon energy dependence of the light-induced NMR signals for GaAs and the GaMnAs film samples were recorded using circularly polarized light. Interpretation of the data was guided by electronic band structure calculations using the k.p method in the presence of an external magnetic field using the modified 8-band Pidgeon-Brown model. The photon energy dependence of the NMR transition intensity exhibited a shift of the absorption band edge; invariance with respect to the sense of helicity of the exciting light; and an absence of oscillations in the photon energy dependence, all of which are consistent with theoretical predictions. The dynamics of the optically activated NMR experiments was investigated by variable optical intensity studies and light/dark modulated optical pumping experiments. This is because doping with Mn (a p-type dopant) can push the Fermi level deep into the valence bands and block the optical transitions (Burstein-Moss effect) needed to create spin polarized electrons. Additionally, the calculated enhancement of the conduction electron g-factor by over two orders of magnitude is expected to quench the electron-nuclear spin angular moment transfer, which impedes the hyperpolarization of lattice nuclei. Experiments with variable light intensity and optical gating reveal a mechanism consistent with light-induced quadrupolar relaxation, a process that will certainly interfere with the optical transfer and storage of quantum information in the lattice nuclear spin states in this material., Comment: Assignment of the experimental optically pumped NMR signals to the Ga(Mn)As film layer, as reported in this manuscript, is probably incorrect and a revised interpretation is currently under consideration

Published
2020

4. Experimental Measurements of Effective Mass in Near Surface InAs Quantum Wells

Author

Yuan, Joseph, Hatefipour, Mehdi, Magill, Brenden A., Mayer, William, Dartiailh, Matthieu C., Sardashti, Kasra, Wickramasinghe, Kaushini S., Khodaparast, Giti A., Matsuda, Yasuhiro H., Kohama, Yoshimitsu, Yang, Zhuo, Thapa, Sunil, Stanton, Christopher J., and Shabani, Javad

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Near surface indium arsenide quantum wells have recently attracted a great deal of interest since they can be interfaced epitaxially with superconducting films and have proven to be a robust platform for exploring mesoscopic and topological superconductivity. In this work, we present magnetotransport properties of two-dimensional electron gases confined to an indium arsenide quantum well near the surface. The electron mass extracted from the envelope of the Shubnikov-de Haas oscillations shows an average effective mass $m^{*}$ = 0.04 at low magnetic field. Complementary to our magnetotransport study, we employed cyclotron resonance measurements and extracted the electron effective mass in the ultra high magnetic field regime. Our measurements show that the effective mass depends on magnetic field in this regime. The data can be understood by considering a model that includes non-parabolicity of the indium arsenide conduction bands.

Published
2019
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6. Soft Phonon Mode Dynamics in Aurivillius Type Structures

Author

Maurya, Deepam, Charkhesht, Ali, Nayak, Sanjeev K., Sun, Fu-Chang, George, Deepu, Pramanick, Abhijit, Kang, Min-Gyu, Song, Hyun-Cheol, Alexander, Marshall M., Lou, Djamila, Khodaparast, Giti A., Alpay, S. Pamir, Vinh, N. Q., and Priya, Shashank

Subjects
Condensed Matter - Materials Science
Abstract

We report the dynamics of soft phonon modes and their role towards the various structural transformations in Aurivillius materials by employing terahertz frequency-domain spectroscopy, atomic pair distribution function analysis, and first-principles calculations. We have chosen Bi4Ti3O12 as a model system and identified soft phonon modes associated with the paraelectric tetragonal to the ferroelectric monoclinic transition. Three soft phonon modes have been discovered which exhibit a strong temperature dependence. We have determined that the anharmonicity in Bi-O bonds plays a significant role in phonon softening and that Bi cations play an important role in the emergence of ferroelectricity., Comment: 4 Figures, supplemental information

Published
2016
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7. Probe and control of photo-excited magnetization precession in Co/Pd multilayer films at low laser fluence regime.

Author

Smith, Nicholas W. G., Pleimling, Yannick, Magill, Brenden A., Mudiyanselage, Rathsara R. H. H., Shenenberger, Alex, Ogawa, Shunta, Nishizawa, Nozomi, Munekata, Hiro, and Khodaparast, Giti A.

Subjects
OPTICAL switching, MAGNETIZATION, MAGNETIC anisotropy, LASERS, SPIN-orbit interactions, MAGNETOOPTICS, MAGNETIC fields, OPTICAL switches
Abstract

We present femtosecond-pulse-induced precession of magnetization at low laser fluence (< 5 μ J / cm 2) regime as a function of magnetic field and laser fluence in three Co/Pd multilayer (ML) systems. These systems belong to three different regimes of magnetic anisotropy that vary with Co thickness (t C o ): in-plane (sample 1, t C o = 0.74 nm), weakly out-of-plane (sample 2, t C o = 0.6 nm), and out-of-plane (sample 3, t C o = 0.40 nm). Interestingly, we observed that the precession amplitudes increase significantly with decreasing the Co layer thickness. In this study, the influence of various spin dynamics and static magneto-optical parameters on precession amplitude is examined critically and compared with a previously proposed analytical expression that connects those quantities. It is found that the enhancement of structural-dependent energy transfer efficiency between charge and spin subsystems is indeed responsible for the observed variations in precession amplitudes. On the basis of this fact, we discuss that the spin–orbit interaction that yields perpendicularly spin-polarized electrons in the MLs through the Co/Pd interface is responsible for the observed increase in precession amplitudes of locally excited magnetization. Our approach of employing low-fluence laser excitation of magnetization precession could be practical for developing a non-thermal, all-optical magnetic switching toward photonic memory applications. [ABSTRACT FROM AUTHOR]

Published
2022
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8. Band structure, g -factor, and spin relaxation in n -type InAsP alloys

Author

Thapa, Sunil K., primary, Mudiyanselage, Rathsara R. H. H., additional, Paleologu, Thalya, additional, Choi, Sukgeun, additional, Yang, Zhuo, additional, Kohama, Y., additional, Matsuda, Y. H., additional, Spencer, Joseph, additional, Magill, Brenden A., additional, Palmstrøm, Chris J., additional, Stanton, Christopher J., additional, and Khodaparast, Giti A., additional

Published
2023
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11. High-sensitivity mid-wave resonant cavity infrared detectors

Author

Razeghi, Manijeh, Khodaparast, Giti A., Vitiello, Miriam S., Kim, C. S., Kim, M., Canedy, C. L., Jackson, E. M., Ellis, C. T., Espinola, R. L., Nolde, J. A., Aifer, E. H., Vurgaftman, I., Meyer, J. R., Jayaraman, V., Kolasa, B., Burgner, C., Knipfer, B., and Marsland, R.

Published
2024
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24. High-performance cavity-enhanced photoacoustic trace-gas sensing

Author

Razeghi, Manijeh, Khodaparast, Giti A., Vitiello, Miriam S., Pelini, Jacopo, Siciliani de Cumis, Mario, Wang, Zhen, Dello Russo, Stefano, Galli, Iacopo, Lopez Garcia, Inaki, Canino, Maria Concetta, Roncaglia, Alberto, Cancio Pastor, Pablo, Akikusa, Naota, Ren, Wei, De Natale, Paolo, and Borri, Simone

Published
2024
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27. Dual-Modal Nanoplasmonic Light Upconversion through Anti-Stokes Photoluminescence and Second-Harmonic Generation from Broadband Multiresonant Metal Nanocavities

Author

Safiabadi Tali, Seied Ali, primary, Mudiyanselage, Rathsara R. H. H., additional, Qian, Yizhou, additional, Smith, Nicholas William Gary, additional, Zhao, Yuming, additional, Morral, Ada, additional, Song, Junyeob, additional, Nie, Meitong, additional, Magill, Brenden A., additional, Khodaparast, Giti A., additional, and Zhou, Wei, additional

Published
2023
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30. Photoluminescence study of non-polar m-plane InGaN and nearly strain-balanced InGaN/AlGaN superlattices.

Author

Cao, Yang, Dzuba, Brandon, Magill, Brenden A., Senichev, Alexander, Nguyen, Trang, Diaz, Rosa E., Manfra, Michael J., McGill, Stephen, Garcia, Carlos, Khodaparast, Giti A., and Malis, Oana

Subjects
MOLECULAR beam epitaxy, PHOTOLUMINESCENCE, X-ray diffraction measurement, THIN films, QUANTUM wells, SUPERLATTICES
Abstract

Photoluminescence (PL) spectroscopy of nonpolar m-plane InGaN thin films with indium composition up to 21% and nearly strain-balanced In0.09Ga0.91N/Al0.19Ga0.81N superlattices grown by plasma-assisted molecular beam epitaxy was performed as a function of temperature. The experimental transition energies are consistently lower than the calculation based on structural parameters extracted from x-ray diffraction measurements. This indicates the presence of indium composition fluctuations in InGaN and hence local bandgap reduction that produces charge localization centers. The spectral width of the low-temperature PL of our m-plane InGaN/AlGaN superlattices is narrower than previously reported for m-plane InGaN/GaN quantum wells grown by MOCVD. The PL integrated intensity drops rapidly, though, as the temperature is increased to 300 K, indicating strong non-radiative recombination at room temperature. Time-resolved PL at low temperatures was performed to characterize the relaxation time scales in an undoped and a doped superlattice. [ABSTRACT FROM AUTHOR]

Published
2020
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31. Electronic and optical properties of highly boron-doped epitaxial Ge/AlAs(001) heterostructures.

Author

Clavel, Michael B., Liu, Jheng-Sin, Meeker, Michael A., Khodaparast, Giti A., Xie, Yuantao, Heremans, Jean J., Bhattacharya, Shuvodip, and Hudait, Mantu K.

Subjects
OPTICAL properties, MOLECULAR beam epitaxy, SPIN-orbit interactions, EPITAXIAL layers, VALENCE bands, BORON
Abstract

The impact of elemental boron (B) doping on the structural, optical, and magnetotransport properties of epitaxial Ge/AlAs/GaAs(001) heterostructures, grown by solid-source molecular beam epitaxy, was comprehensively investigated. Cross-sectional transmission electron microscopy analysis revealed atomically abrupt Ge:B/AlAs and AlAs/GaAs heterointerfaces and a lack of observable long-range defect formation or B segregation in the epitaxial Ge:B layer. Spectral broadening observed in the measured temperature-dependent photoluminescence spectra suggested valence band mixing during recombination, implying a splitting of the valence band heavy- and light-hole degeneracy due to residual strain resulting from substitutional B incorporation in the Ge epilayer. Temperature-dependent magnetotransport analysis of the B-doped Ge thin films exhibited the tell-tale signature of antilocalization, indicating observable spin–orbit interaction in the Ge:B system. Moreover, the temperature- and magnetic field-dependent magnetotransport results indicate the presence of single-carrier, p-type conduction in the Ge:B film, further affirming the successful incorporation and activation of B at a high concentration (∼4 × 1019 cm−3) and elimination of parallel conduction via the large-bandgap AlAs buffer. Together, these results provide insights into the effects of heavy doping (via elemental solid-source doping) on Ge-based heterostructures and their feasibility in future electronic and photonic applications. [ABSTRACT FROM AUTHOR]

Published
2020
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33. Photoluminescence Study of Carrier Localization and Recombination in Nearly Strain‐Balanced Nonpolar InGaN/AlGaN Quantum Wells

Author

Cao, Yang, primary, Dzuba, Brandon, additional, Magill, Brenden A., additional, Senichev, Alexander, additional, Nguyen, Trang, additional, Diaz, Rosa E., additional, Manfra, Michael J., additional, McGill, Stephen, additional, Garcia, Carlos, additional, Khodaparast, Giti A., additional, and Malis, Oana, additional

Published
2022
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35. Novel nitride quantum structures for infrared sensing

Author

Malis, Oana, primary, Nguyen, Trang, additional, Cao, Yang, additional, Magill, Brenden A., additional, Dzuba, Brandon, additional, McGill, Stephen, additional, Garcia, Carlos, additional, Khodaparast, Giti A., additional, and Manfra, Michael J., additional

Published
2022
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36. Carrier recombination dynamics and temperature dependent optical properties of InAs–GaSb heterostructures.

Author

Hudait, Mantu K., Johnston, Steven W., Meeker, Michael, and Khodaparast, Giti A.

Abstract

Heterostructures with two dissimilar materials could offer unprecedented properties if one can carefully synthesize these heterostructures with atomically smooth interfaces and reduced number of recombination centers. InAs/GaSb-based heterostructures have technological importance for long wavelength infrared photodetectors if one can synthesize these materials with high-optical quality and high-carrier lifetime. In this work, the InAs/GaSb heterostructures with a different number of heterointerfaces and growth conditions were grown by solid source molecular beam epitaxy using valved cracker sources for both arsenic and antimony. Precise control of growth parameters and shutter sequences enabled abrupt InAs/GaSb heterointerfaces, as supported by a high-resolution transmission electron microscopic study. The temperature and power-dependent optical properties by photoluminescence (PL) spectroscopic analysis of InAs/GaSb heterostructures with 4 and 28 heterointerfaces displayed donor to the acceptor and the exciton bound to complex defects (VGaGaSb)0. Since the optical transition in PL measurements serves to determine the quality of the material, and the observed excitonic transitions from these InAs/GaSb heterostructures is an indication of high-quality materials. The high-carrier lifetimes of 139 ns to 185 ns from InAs/GaSb heterostructures were measured using microwave photoconductivity decay (μ-PCD) technique at room temperature. The observed increase in carrier lifetime is due to the decreasing number of Ga-related carrier recombination centers or defect complexes. This is further supported by the PL spectroscopic study. In addition, the carrier lifetime with different injection levels is supported by Shockley–Read–Hall recombination. Hence, these InAs/GaSb heterostructures with high-optical quality and high-carrier lifetimes would offer a path for the development of high-performance infrared photodetectors. [ABSTRACT FROM AUTHOR]

Published
2022
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