Browsing by Author "Puretzky, Alexander A."

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    Strain tolerance of two-dimensional crystal growth on curved surfaces
    (AAAS, 2019) Wang, Kai; Puretzky, Alexander A.; Hu, Zhili; Srijanto, Bernadeta R.; Li, Xufan; Gupta, Nitant; Yu, Henry; Tian, Mengkun; Mahjouri-Samani, Masoud; Gao, Xiang; Oyedele, Akinola; Rouleau, Christopher M.; Eres, Gyula; Yakobson, Boris I.; Yoon, Mina; Xiao, Kai; Geohegan, David B.
    Two-dimensional (2D) crystal growth over substrate features is fundamentally guided by the Gauss-Bonnet theorem, which mandates that rigid, planar crystals cannot conform to surfaces with nonzero Gaussian curvature. Here, we reveal how topographic curvature of lithographically designed substrate features govern the strain and growth dynamics of triangular WS2 monolayer single crystals. Single crystals grow conformally without strain over deep trenches and other features with zero Gaussian curvature; however, features with nonzero Gaussian curvature can easily impart sufficient strain to initiate grain boundaries and fractured growth in different directions. Within a strain-tolerant regime, however, triangular single crystals can accommodate considerable (<1.1%) localized strain exerted by surface features that shift the bandgap up to 150 meV. Within this regime, the crystal growth accelerates in specific directions, which we describe using a growth model. These results present a previously unexplored strategy to strain-engineer the growth directions and optoelectronic properties of 2D crystals.
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    Topology stabilized fluctuations in a magnetic nodal semimetal
    (Springer Nature, 2023) Drucker, Nathan C.; Nguyen, Thanh; Han, Fei; Siriviboon, Phum; Luo, Xi; Andrejevic, Nina; Zhu, Ziming; Bednik, Grigory; Nguyen, Quynh T.; Chen, Zhantao; Nguyen, Linh K.; Liu, Tongtong; Williams, Travis J.; Stone, Matthew B.; Kolesnikov, Alexander I.; Chi, Songxue; Fernandez-Baca, Jaime; Nelson, Christie S.; Alatas, Ahmet; Hogan, Tom; Puretzky, Alexander A.; Huang, Shengxi; Yu, Yue; Li, Mingda
    The interplay between magnetism and electronic band topology enriches topological phases and has promising applications. However, the role of topology in magnetic fluctuations has been elusive. Here, we report evidence for topology stabilized magnetism above the magnetic transition temperature in magnetic Weyl semimetal candidate CeAlGe. Electrical transport, thermal transport, resonant elastic X-ray scattering, and dilatometry consistently indicate the presence of locally correlated magnetism within a narrow temperature window well above the thermodynamic magnetic transition temperature. The wavevector of this short-range order is consistent with the nesting condition of topological Weyl nodes, suggesting that it arises from the interaction between magnetic fluctuations and the emergent Weyl fermions. Effective field theory shows that this topology stabilized order is wavevector dependent and can be stabilized when the interband Weyl fermion scattering is dominant. Our work highlights the role of electronic band topology in stabilizing magnetic order even in the classically disordered regime.