Pinaki Sengupta
Degree: PhD
Position: Faculty
Affiliation: NTU Division of Physics
Research Type: Theory
Email: psengupta@ntu.edu.sg
Contact: (65) 6592 1801
Website: http://research.ntu.edu.sg/expertise/academicprofile/pages/StaffProfile.aspx?ST_EMAILID=PSENGUPTA&CategoryDescription=Physics
CA2DM Publications:
2023 |
Foo, D C W; Swain, N; Sengupta, P; Lemarie, G; Adam, S Stabilization mechanism for many-body localization in two dimensions Journal Article PHYSICAL REVIEW RESEARCH , 5 (3), 2023. @article{ISI:001050777700001, title = {Stabilization mechanism for many-body localization in two dimensions }, author = {D C W Foo and N Swain and P Sengupta and G Lemarie and S Adam}, doi = {10.1103/PhysRevResearch.5.L032011}, times_cited = {0}, year = {2023}, date = {2023-07-20}, journal = {PHYSICAL REVIEW RESEARCH }, volume = {5}, number = {3}, publisher = {AMER PHYSICAL SOC }, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA }, abstract = {Experiments in cold-atom systems see almost identical signatures of many-body localization (MBL) in both one-dimensional (d = 1) and two-dimensional (d = 2) systems despite the thermal avalanche hypothesis showing that the MBL phase is unstable ford > 1. Underpinning the thermal avalanche argument is the assumption of exponential localization of local integrals of motion (LIOM). In this Letter we demonstrate that the addition of a confining potential-as is typical in experimental setups-allows a noninteracting disordered system to have superexponentially (Gaussian) localized wave functions, and an interacting disordered system to undergo a localization transition. Moreover, we show that Gaussian localization of MBL LIOM shifts the quantum avalanche critical dimension from d = 1 to d = 2, potentially bridging the divide between the experimental demonstrations of MBL in these systems and existing theoretical arguments that claim that such demonstrations are impossible. }, keywords = {}, pubstate = {published}, tppubtype = {article} } Experiments in cold-atom systems see almost identical signatures of many-body localization (MBL) in both one-dimensional (d = 1) and two-dimensional (d = 2) systems despite the thermal avalanche hypothesis showing that the MBL phase is unstable ford > 1. Underpinning the thermal avalanche argument is the assumption of exponential localization of local integrals of motion (LIOM). In this Letter we demonstrate that the addition of a confining potential-as is typical in experimental setups-allows a noninteracting disordered system to have superexponentially (Gaussian) localized wave functions, and an interacting disordered system to undergo a localization transition. Moreover, we show that Gaussian localization of MBL LIOM shifts the quantum avalanche critical dimension from d = 1 to d = 2, potentially bridging the divide between the experimental demonstrations of MBL in these systems and existing theoretical arguments that claim that such demonstrations are impossible. |
2019 |
Tang, Ho-Kin; Leaw, J N; Rodrigues, J N B; Herbut, I F; Sengupta, P; Assaad, F F; Adam, S Response to Comment on "The role of electron-electron interactions in two-dimensional Dirac fermions" Journal Article SCIENCE, 366 (6470), 2019, ISSN: 0036-8075. @article{ISI:000502662500002, title = {Response to Comment on "The role of electron-electron interactions in two-dimensional Dirac fermions"}, author = {Ho-Kin Tang and J N Leaw and J N B Rodrigues and I F Herbut and P Sengupta and F F Assaad and S Adam}, doi = {10.1126/science.aav8877}, times_cited = {1}, issn = {0036-8075}, year = {2019}, date = {2019-12-06}, journal = {SCIENCE}, volume = {366}, number = {6470}, publisher = {AMER ASSOC ADVANCEMENT SCIENCE}, address = {1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA}, abstract = {Hesselmann et al. question one of our conclusions: the suppression of Fermi velocity at the Gross-Neveu critical point for the specific case of vanishing long-range interactions and at zero energy. The possibility they raise could occur in any finite-size extrapolation of numerical data. Although we cannot definitively rule out this possibility, we provide mathematical bounds on its likelihood.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Hesselmann et al. question one of our conclusions: the suppression of Fermi velocity at the Gross-Neveu critical point for the specific case of vanishing long-range interactions and at zero energy. The possibility they raise could occur in any finite-size extrapolation of numerical data. Although we cannot definitively rule out this possibility, we provide mathematical bounds on its likelihood. |
Leaw, Jia Ning; Tang, Ho-Kin; Sengupta, Pinaki; Assaad, Fakher F; Herbut, Igor F; Adam, Shaffique Electronic ground state in bilayer graphene with realistic Coulomb interactions Journal Article PHYSICAL REVIEW B, 100 (12), 2019, ISSN: 2469-9950. @article{ISI:000485193000002, title = {Electronic ground state in bilayer graphene with realistic Coulomb interactions}, author = {Jia Ning Leaw and Ho-Kin Tang and Pinaki Sengupta and Fakher F Assaad and Igor F Herbut and Shaffique Adam}, doi = {10.1103/PhysRevB.100.125116}, times_cited = {6}, issn = {2469-9950}, year = {2019}, date = {2019-09-06}, journal = {PHYSICAL REVIEW B}, volume = {100}, number = {12}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {Both insulating and conducting electronic behaviors have been experimentally seen in clean bilayer graphene samples at low temperature, and there is still no consensus on the nature of the interacting ground state at half filling and in the absence of a magnetic field. Theoretically, several possibilities for the insulating ground states have been predicted for weak interaction strength. However, a recent renormalization-group calculation on a Hubbard model for charge-neutral bilayer graphene with short-range interactions suggests the emergence of low-energy Dirac fermions that would stabilize the metallic phase for weak interactions. Using a nonperturbative projective quantum Monte Carlo, we calculate the ground state for bilayer graphene using a realistic model for the Coulomb interaction that includes both short-range and long-range contributions. We find that a finite critical on-site interaction is needed to gap bilayer graphene and the transition belongs to the Gross-Neveu universality class, thereby confirming the Hubbard model expectations even in the presence of a long-range Coulomb potential, in agreement with our theoretical analysis. In addition, we also find that the critical on-site interactions necessary to destabilize the metallic ground state decrease with increasing interlayer coupling.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Both insulating and conducting electronic behaviors have been experimentally seen in clean bilayer graphene samples at low temperature, and there is still no consensus on the nature of the interacting ground state at half filling and in the absence of a magnetic field. Theoretically, several possibilities for the insulating ground states have been predicted for weak interaction strength. However, a recent renormalization-group calculation on a Hubbard model for charge-neutral bilayer graphene with short-range interactions suggests the emergence of low-energy Dirac fermions that would stabilize the metallic phase for weak interactions. Using a nonperturbative projective quantum Monte Carlo, we calculate the ground state for bilayer graphene using a realistic model for the Coulomb interaction that includes both short-range and long-range contributions. We find that a finite critical on-site interaction is needed to gap bilayer graphene and the transition belongs to the Gross-Neveu universality class, thereby confirming the Hubbard model expectations even in the presence of a long-range Coulomb potential, in agreement with our theoretical analysis. In addition, we also find that the critical on-site interactions necessary to destabilize the metallic ground state decrease with increasing interlayer coupling. |
2018 |
Tang, Ho-Kin; Leaw, J N; Rodrigues, J N B; Herbut, I F; Sengupta, P; Assaad, F F; Adam, S The role of electron-electron interactions in two-dimensional Dirac fermions Journal Article SCIENCE, 361 (6402), pp. 570-574, 2018, ISSN: 0036-8075. @article{ISI:000441202700029, title = {The role of electron-electron interactions in two-dimensional Dirac fermions}, author = {Ho-Kin Tang and J N Leaw and J N B Rodrigues and I F Herbut and P Sengupta and F F Assaad and S Adam}, doi = {10.1126/science.aao2934}, times_cited = {0}, issn = {0036-8075}, year = {2018}, date = {2018-08-10}, journal = {SCIENCE}, volume = {361}, number = {6402}, pages = {570-574}, publisher = {AMER ASSOC ADVANCEMENT SCIENCE}, address = {1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA}, abstract = {The role of electron-electron interactions in two-dimensional Dirac fermion systems remains enigmatic. Using a combination of nonperturbative numerical and analytical techniques that incorporate both the contact and long-range parts of the Coulomb interaction, we identify the two previously discussed regimes: a Gross-Neveu transition to a strongly correlated Mott insulator and a semimetallic state with a logarithmically diverging Fermi velocity accurately described by the random phase approximation. We predict that experimental realizations of Dirac fermions span this crossover and that this determines whether the Fermi velocity is increased or decreased by interactions. We explain several long-standing mysteries, including why the observed Fermi velocity in graphene is consistently about 20% larger than values obtained from ab initio calculations and why graphene on different substrates shows different behaviors.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The role of electron-electron interactions in two-dimensional Dirac fermion systems remains enigmatic. Using a combination of nonperturbative numerical and analytical techniques that incorporate both the contact and long-range parts of the Coulomb interaction, we identify the two previously discussed regimes: a Gross-Neveu transition to a strongly correlated Mott insulator and a semimetallic state with a logarithmically diverging Fermi velocity accurately described by the random phase approximation. We predict that experimental realizations of Dirac fermions span this crossover and that this determines whether the Fermi velocity is increased or decreased by interactions. We explain several long-standing mysteries, including why the observed Fermi velocity in graphene is consistently about 20% larger than values obtained from ab initio calculations and why graphene on different substrates shows different behaviors. |
2015 |
Tang, Ho-Kin; Laksono, E; Rodrigues, J N B; Sengupta, P; Assaad, F F; Adam, S Interaction-Driven Metal-Insulator Transition in Strained Graphene Journal Article PHYSICAL REVIEW LETTERS, 115 (18), 2015, ISSN: 0031-9007. @article{ISI:000363788400006, title = {Interaction-Driven Metal-Insulator Transition in Strained Graphene}, author = {Ho-Kin Tang and E Laksono and J N B Rodrigues and P Sengupta and F F Assaad and S Adam}, doi = {10.1103/PhysRevLett.115.186602}, times_cited = {0}, issn = {0031-9007}, year = {2015}, date = {2015-10-30}, journal = {PHYSICAL REVIEW LETTERS}, volume = {115}, number = {18}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {The question of whether electron-electron interactions can drive a metal to insulator transition in graphene under realistic experimental conditions is addressed. Using three representative methods to calculate the effective long-range Coulomb interaction between pi electrons in graphene and solving for the ground state using quantum Monte Carlo methods, we argue that, without strain, graphene remains metallic and changing the substrate from SiO2 to suspended samples hardly makes any difference. In contrast, applying a rather large-but experimentally realistic-uniform and isotropic strain of about 15% seems to be a promising route to making graphene an antiferromagnetic Mott insulator.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The question of whether electron-electron interactions can drive a metal to insulator transition in graphene under realistic experimental conditions is addressed. Using three representative methods to calculate the effective long-range Coulomb interaction between pi electrons in graphene and solving for the ground state using quantum Monte Carlo methods, we argue that, without strain, graphene remains metallic and changing the substrate from SiO2 to suspended samples hardly makes any difference. In contrast, applying a rather large-but experimentally realistic-uniform and isotropic strain of about 15% seems to be a promising route to making graphene an antiferromagnetic Mott insulator. |
Su, Lei; Sengupta, Pinaki Dimer-induced heavy-fermion superconductivity in the Shastry-Sutherland Kondo lattice model Journal Article PHYSICAL REVIEW B, 92 (16), 2015, ISSN: 1098-0121. @article{ISI:000363521100003, title = {Dimer-induced heavy-fermion superconductivity in the Shastry-Sutherland Kondo lattice model}, author = {Lei Su and Pinaki Sengupta}, doi = {10.1103/PhysRevB.92.165431}, times_cited = {0}, issn = {1098-0121}, year = {2015}, date = {2015-10-27}, journal = {PHYSICAL REVIEW B}, volume = {92}, number = {16}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {We study the Kondo lattice model on the geometrically frustrated Shastry-Sutherland lattice focusing on the quantum phase transition between the valence bond solid and the heavy fermion liquid phase. By explicitly including spinon pairing of local moments at the mean-field level, we establish the emergence of a unique heavy fermion superconducting phase induced by dimer ordering of the local moments coexisting with Kondo hybridization. Furthermore, we demonstrate that for suitable choices of parameters, a partial Kondo-screening phase, where some of the valence bonds are broken, precedes the aforementioned dimer-induced superconducting phase. Our results have important implications for understanding the experimental observations in the heavy fermion Shastry-Sutherland compounds.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the Kondo lattice model on the geometrically frustrated Shastry-Sutherland lattice focusing on the quantum phase transition between the valence bond solid and the heavy fermion liquid phase. By explicitly including spinon pairing of local moments at the mean-field level, we establish the emergence of a unique heavy fermion superconducting phase induced by dimer ordering of the local moments coexisting with Kondo hybridization. Furthermore, we demonstrate that for suitable choices of parameters, a partial Kondo-screening phase, where some of the valence bonds are broken, precedes the aforementioned dimer-induced superconducting phase. Our results have important implications for understanding the experimental observations in the heavy fermion Shastry-Sutherland compounds. |