Pinaki Sengupta

@article{ISI:001511184900009,
title = {Engineering many-body quantum Hamiltonians with nonergodic properties using quantum Monte Carlo},
author = {Nyayabanta Swain and Ho-Kin Tang and Darryl Chuan Wei Foo and Brian J J Khor and Gabriel Lemarie and Fakher F Assaad and Pinaki Sengupta and Shaffique Adam},
doi = {10.1103/PhysRevB.111.224201},
times_cited = {0},
issn = {2469-9950},
year = {2025},
date = {2025-06-02},
journal = {PHYSICAL REVIEW B},
volume = {111},
number = {22},
publisher = {AMER PHYSICAL SOC},
address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA},
abstract = {We present a computational framework to identify Hamiltonians of interacting quantum many-body systems that host nonergodic excited states. We combine quantum Monte Carlo simulations with the recently proposed eigenstate-to-Hamiltonian construction, which maps the ground state of a specified parent Hamiltonian to a single nonergodic excited state of a new derived Hamiltonian. This engineered Hamiltonian contains nontrivial, systematically-obtained, and emergent features that are responsible for its nonergodic properties. We demonstrate this approach by applying it to quantum many-body scar states where we discover a previously unreported family of Hamiltonians with spatially oscillating spin exchange couplings that host scar-like properties, including revivals in the quantum dynamics, and towers in the inverse participation ratio; and to many-body localization, where we find a two-dimensional Hamiltonian with correlated disorder that exhibits nonergodic scaling of the participation entropy and inverse participation ratios of order unity. The method can be applied to other known ground states to discover new quantum many-body systems with nonergodic excited states.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:001334829900007,
title = {Spectral functions of lattice fermions on the honeycomb lattice with Hubbard and long-range Coulomb interactions},
author = {Ho-Kin Tang and Indra Yudhistira and Udvas Chattopadhyay and Maksim Ulybyshev and P Sengupta and F F Assaad and S Adam},
doi = {10.1103/PhysRevB.110.155120},
times_cited = {3},
issn = {2469-9950},
year = {2024},
date = {2024-10-09},
journal = {PHYSICAL REVIEW B},
volume = {110},
number = {15},
publisher = {AMER PHYSICAL SOC},
address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA},
abstract = {The absence of screening of the nonlocal Coulomb interaction in Dirac systems at charge neutrality leads to the breakdown of the Fermi liquid and divergence of the Fermi velocity. On the other hand, Mott-Hubbard physics and the concomitant formation of local moments is dominated by the local effective Hubbard interaction. Using quantum Monte Carlo methods combined with stochastic analytical continuation, we compute the single particle spectral function of fermions on the honeycomb lattice for a realistic interaction that includes both the Hubbard interaction and long-ranged Coulomb repulsion. To a first approximation, we find that the generic high-energy features, such as the formation of the upper Hubbard band near the phase transition, are primarily determined by the local effective Hubbard interaction. In the weakly interacting regime, the long-range Coulomb interaction enhances the bandwidth of quasiparticles and suppresses their lifetime. Conversely, near the phase transition, the long-range Coulomb interaction suppresses the background antiferromagnetic fluctuation, which potentially promotes the propagation of spin polarons, leading to a slight enhancement of the quasiparticle spectral weight and lifetime.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}