Akshat Pandey
Ph.D. Student in Physics, admitted Autumn 2020
All Publications
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Bipartite Sachdev-Ye models with Read-Saleur symmetries
PHYSICAL REVIEW B
2024; 110 (12)
View details for DOI 10.1103/PhysRevB.110.125140
View details for Web of Science ID 001320325600005
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Critical behavior of dirty free parafermionic chains
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
2024; 57 (33)
View details for DOI 10.1088/1751-8121/ad6723
View details for Web of Science ID 001284813500001
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Emergent tetragonality in a fundamentally orthorhombic material.
Science advances
2024; 10 (21): eadk3321
Abstract
Symmetry plays a key role in determining the physical properties of materials. By Neumann's principle, the properties of a material remain invariant under the symmetry operations of the space group to which the material belongs. Continuous phase transitions are associated with a spontaneous reduction in symmetry. Less common are examples where proximity to a continuous phase transition leads to an increase in symmetry. We find signatures of an emergent tetragonal symmetry close to a charge density wave (CDW) bicritical point in a fundamentally orthorhombic material, ErTe3, for which the two distinct CDW phase transitions are tuned via anisotropic strain. We first establish that tension along the a axis favors an abrupt rotation of the CDW wave vector from the c to a axis and infer the presence of a bicritical point where the two continuous phase transitions meet. We then observe a divergence of the nematic elastoresistivity approaching this putative bicritical point, indicating an emergent tetragonality in the critical behavior.
View details for DOI 10.1126/sciadv.adk3321
View details for PubMedID 38781340
View details for PubMedCentralID PMC11114214
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Emergent Z2 symmetry near a charge density wave multicritical point
PHYSICAL REVIEW B
2023; 108 (20)
View details for DOI 10.1103/PhysRevB.108.205141
View details for Web of Science ID 001112328100006
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Random geometry at an infinite-randomness fixed point
PHYSICAL REVIEW B
2023; 108 (6)
View details for DOI 10.1103/PhysRevB.108.064201
View details for Web of Science ID 001122909100002
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A stability bound on the [Formula: see text]-linear resistivity of conventional metals.
Proceedings of the National Academy of Sciences of the United States of America
2023; 120 (3): e2216241120
Abstract
Perturbative considerations account for the properties of conventional metals, including the range of temperatures where the transport scattering rate is 1/τtr = 2πλT, where λ is a dimensionless strength of the electron-phonon coupling. The fact that measured values satisfy λ ≲ 1 has been noted in the context of a possible "Planckian" bound on transport. However, since the electron-phonon scattering is quasielastic in this regime, no such Planckian considerations can be relevant. We present and analyze Monte Carlo results on the Holstein model which show that a different sort of bound is at play: a "stability" bound on λ consistent with metallic transport. We conjecture that a qualitatively similar bound on the strength of residual interactions, which is often stronger than Planckian, may apply to metals more generally.
View details for DOI 10.1073/pnas.2216241120
View details for PubMedID 36634139
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Interstitial-Induced Ferromagnetism in a Two-Dimensional Wigner Crystal.
Physical review letters
2022; 129 (22): 227202
Abstract
The two-dimensional Wigner crystal (WC) occurs in the strongly interacting regime (r_{s}≫1) of the two-dimensional electron gas (2DEG). The magnetism of a pure WC is determined by tunneling processes that induce multispin ring-exchange interactions, resulting in fully polarized ferromagnetism for large enough r_{s}. Recently, Hossain et al. [Proc. Natl. Acad. Sci. U.S.A. 117, 32244 (2020)PNASA60027-842410.1073/pnas.2018248117] reported the occurrence of a fully polarized ferromagnetic insulator at r_{s}≳35 in an AlAs quantum well, but at temperatures orders of magnitude larger than the predicted exchange energies for the pure WC. Here, we analyze the large r_{s} dynamics of an interstitial defect in the WC, and show that it produces local ferromagnetism with much higher energy scales. Three hopping processes are dominant, which favor a large, fully polarized ferromagnetic polaron. Based on the above results, we speculate concerning the phenomenology of the magnetism near the metal-insulator transition of the 2DEG.
View details for DOI 10.1103/PhysRevLett.129.227202
View details for PubMedID 36493455