Chan, Julia Y.
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/4226
Julia Chan is Professor of Solid State and Materials Chemistry in the Department of Chemistry and head of The Chan Lab. Dr. Chan's research "is focused on crystal growth, structure (X-ray and neutron), and characterization (electrical, magnetic, transport) of intermetallics and oxides for energy applications, including:
- Highly correlated electronic materials
- Magnetic frustrated materials
- Search and discovery of intermetallics with low thermal conductivity"
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Elected Fellow of the American Association for the Advancement of Science (AAAS) in November 2019.
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Browsing Chan, Julia Y. by Author "Balicas, L."
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Item Bulk Fermi Surface of The Weyl Type-II Semimetallic Candidate NbIrTe₄(American Physical Society, 2019-05-15) Schönemann, R.; Chiu, Y. -C; Zheng, W.; Quito, V. L.; Sur, S.; McCandless, Gregory T.; Chan, Julia Y.; Balicas, L.; 0000-0003-4434-2160 (Chan, JY); McCandless, Gregory T.; Chan, Julia Y.Recently, a new group of layered transition-metal tetra-chalcogenides was proposed via first-principles calculations to correspond to a new family of Weyl type-II semimetals with promising topological properties in the bulk as well as in the monolayer limit. In this paper, we present measurements of the Shubnikov-de Haas (SdH) and de Haas-van Alphen effects under high magnetic fields for the type-II Weyl semimetallic candidate NbIrTe₄. We find that the angular dependence of the observed Fermi surface extremal cross-sectional areas agree well with our density functional theory (DFT) calculations supporting the existence of Weyl type-II points in this material. Although we observe a large and nonsaturating magnetoresistivity in NbIrTe4 under fields all the way up to 35T, Hall-effect measurements indicate that NbIrTe₄ is not a compensated semimetal. The transverse magnetoresistivity displays a fourfold angular dependence akin to the so-called butterfly magnetoresistivity observed in nodal line semimetals. We conclude that the magnetoresistivity and its unconventional angular dependence are governed by the topography of the Fermi surface and the resulting anisotropy in effective masses and in carrier mobilities. © 2019 American Physical Society.Item Detailed Study of the Fermi Surfaces of the Type-II Dirac Semimetallic Candidates XTe₂ (X =Pd, Pt)(American Physical Society) Zheng, W.; Schönemann, R.; Aryal, N.; Zhou, Q.; Rhodes, D.; Chiu, Y. -C; Chen, K. -W; Kampert, E.; Förster, T.; Martin, T. J.; McCandless, Gregory T.; Chan, Julia Y.; Manousakis, E.; Balicas, L.; 0000-0003-4434-2160 (Chan, JY); Martin, T. J.; McCandless, Gregory T.; Chan, Julia Y.We present a detailed quantum oscillatory study on the Dirac type-II semimetallic candidates PdTe₂ and PtTe₂ via the temperature and the angular dependence of the de Haas-van Alphen and Shubnikov-de Haas effects. In high-quality single crystals of both compounds, i.e., displaying carrier mobilities between 10³ and 10⁴ cm²/Vs, we observed a large nonsaturating magnetoresistivity which in PtTe₂ at a temperature T=1.3 K leads to an increase in the resistivity up to (5×10⁴)% under a magnetic field μ₀H=62 T. These high mobilities correlate with their light effective masses in the range of 0.04 to 1 bare electron mass according to our measurements. For PdTe₂ the experimentally determined Fermi surface cross-sectional areas show excellent agreement with those resulting from band structure calculations. Surprisingly, this is not the case for PtTe₂, whose agreement between calculations and experiments is relatively poor even when electronic correlations are included in the calculations. Therefore, our study provides strong support for the existence of a Dirac type-II node in PdTe₂ and probably also for PtTe₂. Band structure calculations indicate that the topologically nontrivial bands of PtTe₂ do not cross the Fermi level. In contrast, for PdTe₂ the Dirac type-II cone does intersect, although our calculations also indicate that the associated cyclotron orbit on the Fermi surface is located in a distinct k_z plane with respect to that of the Dirac type-II node. Therefore, it should yield a trivial Berry phase.Item Fermi Surface of the Weyl Type-II Metallic Candidate WP₂(2018-09-12) Schönemann, R.; Aryal, N.; Zhou, Q.; Chiu, Y. -C; Chen, K. -W; Martin, T. J.; McCandless, G. T.; Chan, Julia Y.; Manousakis, E.; Balicas, L.; Martin, T. J.; McCandless, G. T.; Chan, Julia Y.Weyl type-II fermions are massless quasiparticles that obey the Weyl equation and which are predicted to occur at the boundary between electron and hole pockets in certain semimetals, i.e., the (W,Mo)(Te₁,P)₂ compounds. Here, we present a study of the Fermi surface of WP₂ via the Shubnikov-de Haas (SdH) effect. Compared to other semimetals, WP₂ exhibits a very low residual resistivity, i.e., ρ₀≃10 nΩ cm, which leads to perhaps the largest nonsaturating magnetoresistivity [ρ(H)] reported for any compound. For the samples displaying the smallest ρ₀, ρ(H) is observed to increase by a factor of 2.5×10⁷% under μ₀H=35 T at T=0.35 K. The angular dependence of the SdH frequencies is found to be in excellent agreement with the first-principles calculations when the electron and hole bands are shifted by 30 meV with respect to the Fermi level. This small discrepancy could have implications for the predicted topological character of this compound.