Detection of Nontrivial Topology Driven by Charge Density Wave in a Semi-Dirac Metal |
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Authors: | Rafiqul Alam Prasun Boyal Shubhankar Roy Ratnadwip Singha Buddhadeb Pal Riju Pal Prabhat Mandal Priya Mahadevan Atindra Nath Pal |
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Affiliation: | 1. Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, Sector III, Block JD, Salt Lake, Kolkata, 700106 India;2. Saha Institute of Nuclear Physics, Homi Bhabha National Institute, 1/AF Bidhannagar, Kolkata, 700064 India;3. Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, Sector III, Block JD, Salt Lake, Kolkata, 700106 India Saha Institute of Nuclear Physics, Homi Bhabha National Institute, 1/AF Bidhannagar, Kolkata, 700064 India |
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Abstract: | The presence of electron correlations in a system with topological order can lead to exotic ground states. Considering single crystals of LaAgSb2 which has a square net crystal structure, one finds multiple charge density wave transitions (CDW) as the temperature is lowered. Large planar Hall (PHE) signals are found in the CDW phase, which are still finite in the high-temperature phase though they change sign. Optimizing the structure within first-principles calculations, one finds an unusual chiral metallic phase. This is because as the temperature is lowered, the separation between the Ag/Sb atoms on different layers decreases, leading to stronger repulsions between electrons associated with atoms on different layers. This leads to successive layers sliding with respect to each other, thereby stabilizing a chiral structure in which inversion symmetry is also broken. The large Berry curvature associated with the low-temperature structure explains the low-temperature PHE. At high temperature, the PHE arises from the changes induced in the anisotropic Dirac cone in presence of a magnetic field. This work represents a route toward detecting and understanding the mechanism in a correlation-driven topological transition through electron transport measurements, complemented by ab-initio electronic structure calculations. |
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Keywords: | charge density waves dirac semimetal planar hall effects square net topology |
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