Rice University Research Repository
The Rice Research Repository (R-3) provides access to research produced at Rice University, including theses and dissertations, journal articles, research center publications, datasets, and academic journals. Managed by Fondren Library, R-3 is indexed by Google and Google Scholar, follows best practices for preservation, and provides DOIs to facilitate citation. Woodson Research Center collections, including Rice Images and Documents and the Task Force on Slavery, Segregation, and Racial Injustice, have moved here.
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Recent Submissions
Why should the U.S. Invest in Science, Technology, and Innovation?
(Rice University, 2024) Sapkota, Aastha; Baker Institute Science and Technology Policy Program
In recent years, the United States' leadership in global R&D has shown signs of decline, raising urgent concerns about its future economic and technological competitiveness. A primary contributing factor to this trend is the pressing need for more investment in science, technology, engineering, and mathematics (STEM) fields within the country. With an emphasis on the US position, this study examines how R&D outputs and expenditures are changing globally. A comparative analysis with China and other leading countries highlights how China's increasing investment in STEM fields might pose a challenge to America's position as the world leader in innovation and technology. Utilizing economic frameworks such as the Solow and Romer models, this study also examines how technological advancement facilitates sustained economic growth over the long term. This project explores whether the United States' future economic potential will be severely compromised by the country's present underfunding of STEM research programs, potentially leading to a significant loss of global competitiveness, a prospect that could shift American hegemony and tip the scales of Western economic power.
Observation of flat bands and Dirac cones in a pyrochlore lattice superconductor
(Springer Nature, 2024) Huang, Jianwei; Setty, Chandan; Deng, Liangzi; You, Jing-Yang; Liu, Hongxiong; Shao, Sen; Oh, Ji Seop; Guo, Yucheng; Zhang, Yichen; Yue, Ziqin; Yin, Jia-Xin; Hashimoto, Makoto; Lu, Donghui; Gorovikov, Sergey; Dai, Pengcheng; Denlinger, Jonathan D.; Allen, J. W.; Hasan, M. Zahid; Feng, Yuan-Ping; Birgeneau, Robert J.; Shi, Youguo; Chu, Ching-Wu; Chang, Guoqing; Si, Qimiao; Yi, Ming; Rice Center for Quantum Materials
Emergent phases often appear when the electronic kinetic energy is comparable to the Coulomb interactions. One approach to seek material systems as hosts of such emergent phases is to realize localization of electronic wavefunctions due to the geometric frustration inherent in the crystal structure, resulting in flat electronic bands. Recently, such efforts have found a wide range of exotic phases in the two-dimensional kagome lattice, including magnetic order, time-reversal symmetry breaking charge order, nematicity, and superconductivity. However, the interlayer coupling of the kagome layers disrupts the destructive interference needed to completely quench the kinetic energy. Here we demonstrate that an interwoven kagome network—a pyrochlore lattice—can host a three dimensional (3D) localization of electron wavefunctions. Meanwhile, the nonsymmorphic symmetry of the pyrochlore lattice guarantees all band crossings at the Brillouin zone X point to be 3D gapless Dirac points, which was predicted theoretically but never yet observed experimentally. Through a combination of angle-resolved photoemission spectroscopy, fundamental lattice model and density functional theory calculations, we investigate the novel electronic structure of a Laves phase superconductor with a pyrochlore sublattice, CeRu2. We observe evidence of flat bands originating from the Ce 4f orbitals as well as flat bands from the 3D destructive interference of the Ru 4d orbitals. We further observe the nonsymmorphic symmetry-protected 3D gapless Dirac cone at the X point. Our work establishes the pyrochlore structure as a promising lattice platform to realize and tune novel emergent phases intertwining topology and many-body interactions.
Resolved ALMA observations of water in the inner astronomical units of the HL Tau disk
(Springer Nature, 2024) Facchini, Stefano; Testi, Leonardo; Humphreys, Elizabeth; Vander Donckt, Mathieu; Isella, Andrea; Wrzosek, Ramon; Baudry, Alain; Gray, Malcom D.; Richards, Anita M. S.; Vlemmmings, Wouter
The water molecule is a key ingredient in the formation of planetary systems, with the water snowline being a favourable location for the growth of massive planetary cores. Here we present Atacama Large Millimeter/submillimeter Array data of the ringed protoplanetary disk orbiting the young star HL Tauri that show centrally peaked, bright emission arising from three distinct transitions of the main water isotopologue ($${\mathrm{H}}_{2}^{16}{\mathrm{O}}$$). The spatially and spectrally resolved water content probes gas in a thermal range down to the water sublimation temperature. Our analysis implies a stringent lower limit of 3.7 Earth oceans of water vapour available within the inner 17 astronomical units of the system. We show that our observations are limited to probing the water content in the atmosphere of the disk, due to the high dust column density and absorption, and indicate that the main water isotopologue is the best tracer to spatially resolve water vapour in protoplanetary disks.
Reversible non-volatile electronic switching in a near-room-temperature van der Waals ferromagnet
(Springer Nature, 2024) Wu, Han; Chen, Lei; Malinowski, Paul; Jang, Bo Gyu; Deng, Qinwen; Scott, Kirsty; Huang, Jianwei; Ruff, Jacob P. C.; He, Yu; Chen, Xiang; Hu, Chaowei; Yue, Ziqin; Oh, Ji Seop; Teng, Xiaokun; Guo, Yucheng; Klemm, Mason; Shi, Chuqiao; Shi, Yue; Setty, Chandan; Werner, Tyler; Hashimoto, Makoto; Lu, Donghui; Yilmaz, Turgut; Vescovo, Elio; Mo, Sung-Kwan; Fedorov, Alexei; Denlinger, Jonathan D.; Xie, Yaofeng; Gao, Bin; Kono, Junichiro; Dai, Pengcheng; Han, Yimo; Xu, Xiaodong; Birgeneau, Robert J.; Zhu, Jian-Xin; da Silva Neto, Eduardo H.; Wu, Liang; Chu, Jiun-Haw; Si, Qimiao; Yi, Ming; Rice Center for Quantum Materials
Non-volatile phase-change memory devices utilize local heating to toggle between crystalline and amorphous states with distinct electrical properties. Expanding on this kind of switching to two topologically distinct phases requires controlled non-volatile switching between two crystalline phases with distinct symmetries. Here, we report the observation of reversible and non-volatile switching between two stable and closely related crystal structures, with remarkably distinct electronic structures, in the near-room-temperature van der Waals ferromagnet Fe5−δGeTe2. We show that the switching is enabled by the ordering and disordering of Fe site vacancies that results in distinct crystalline symmetries of the two phases, which can be controlled by a thermal annealing and quenching method. The two phases are distinguished by the presence of topological nodal lines due to the preserved global inversion symmetry in the site-disordered phase, flat bands resulting from quantum destructive interference on a bipartite lattice, and broken inversion symmetry in the site-ordered phase.
Association of education attainment, smoking status, and alcohol use disorder with dementia risk in older adults: a longitudinal observational study
(Springer Nature, 2024) Tang, Huilin; Shaaban, C. Elizabeth; DeKosky, Steven T.; Smith, Glenn E.; Hu, Xia; Jaffee, Michael; Salloum, Ramzi G.; Bian, Jiang; Guo, Jingchuan
Previous research on the risk of dementia associated with education attainment, smoking status, and alcohol use disorder (AUD) has yielded inconsistent results, indicating potential heterogeneous treatment effects (HTEs) of these factors on dementia risk. Thus, this study aimed to identify the important variables that may contribute to HTEs of these factors in older adults.