Quek Su Ying

@article{ISI:001309683400002,
title = {Tunable viscous layers in Corbino geometry using density junctions},
author = {Ramal Afrose and Aydin Cem Keser and Oleg P Sushkov and Shaffique Adam},
doi = {10.1103/PhysRevB.110.125409},
times_cited = {0},
issn = {2469-9950},
year = {2024},
date = {2024-09-06},
journal = {PHYSICAL REVIEW B},
volume = {110},
number = {12},
publisher = {AMER PHYSICAL SOC},
address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA},
abstract = {In sufficiently clean materials where electron-electron interactions are strong compared to momentum-relaxing scattering processes, electron transport resembles the flow of a viscous fluid. We study hydrodynamic electron transport across density interfaces (n-n junctions) in a 2DEG in the Corbino geometry. From numerical simulations in COMSOL using realistic parameters, we show that we can produce tunable viscous layers at the density interface by varying the density ratio of charge carriers. We quantitatively explain this observation with simple analytic expressions together with boundary conditions at the interface. We also show signatures of these viscous layers in the magnetoresistance. Breaking down viscous and Ohmic contributions, we find that when the outer radial region of the Corbino has higher charge density compared to the inner region, the viscous layers at the interface serve to suppress the magnetoresistance produced by momentum-relaxing scattering. Conversely, the magnetoresistance is enhanced when the inner region has higher density than the outer. Our results add to the repertoire of techniques for engineering viscous electron flows, which hold a promise for applications in future electronic devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000684262800001,
title = {Geometric Control of Universal Hydrodynamic Flow in a Two-Dimensional Electron Fluid},
author = {Aydin Cem Keser and Daisy Q Wang and Oleh Klochan and Derek Y H Ho and Olga A Tkachenko and Vitaly A Tkachenko and Dimitrie Culcer and Shaffique Adam and Ian Farrer and David A Ritchie and Oleg P Sushkov and Alexander R Hamilton},
doi = {10.1103/PhysRevX.11.031030},
times_cited = {45},
issn = {2160-3308},
year = {2021},
date = {2021-08-06},
journal = {PHYSICAL REVIEW X},
volume = {11},
number = {3},
publisher = {AMER PHYSICAL SOC},
address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA},
abstract = {Fluid dynamics is one of the cornerstones of modern physics and has recently found applications in the transport of electrons in solids. In most solids, electron transport is dominated by extrinsic factors, such as sample geometry and scattering from impurities. However, in the hydrodynamic regime, Coulomb interactions transform the electron motion from independent particles to the collective motion of a viscous "electron fluid." The fluid viscosity is an intrinsic property of the electron system, determined solely by the electron-electron interactions. Resolving the universal intrinsic viscosity is challenging, as it affects the resistance only through interactions with the sample boundaries, whose roughness not only is unknown but also varies from device to device. Here, we eliminate all unknown parameters by fabricating samples with smooth sidewalls to achieve the perfect slip boundary condition, which has been elusive in both molecular fluids and electronic systems. We engineer the device geometry to create viscous dissipation and reveal the true intrinsic hydrodynamic properties of a 2D system. We observe a clear transition from ballistic to hydrodynamic electron motion, driven by both temperature and magnetic field. We directly measure the viscosity and electron-electron scattering lifetime (the Fermi quasiparticle lifetime) over a wide temperature range without fitting parameters and show they have a strong dependence on electron density that cannot be explained by conventional theories based on the random phase approximation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000465159300001,
title = {Gauge-phonon dominated resistivity in twisted bilayer graphene near magic angle},
author = {Indra Yudhistira and Nilotpal Chakraborty and Girish Sharma and Derek Y H Ho and Evan Laksono and Oleg P Sushkov and Giovanni Vignale and Shaffique Adam},
doi = {10.1103/PhysRevB.99.140302},
times_cited = {30},
issn = {2469-9950},
year = {2019},
date = {2019-04-17},
journal = {PHYSICAL REVIEW B},
volume = {99},
number = {14},
publisher = {AMER PHYSICAL SOC},
address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA},
abstract = {Recent experiments on twisted bilayer graphene (tBG) close to magic angle show that a small relative rotation in a van der Waals heterostructure greatly alters its electronic properties. We consider various scattering mechanisms and show that the carrier transport in tBG is dominated by a combination of charged impurities and acoustic gauge phonons. Charged impurities still dominate at low temperature and densities because of the inability of Dirac fermions to screen long-range Coulomb potentials at charge neutrality; however, the gauge phonons dominate for most of the experimental regime because, although they couple to current, they do not induce charge and are therefore unscreened by the large density of states close to magic angle. We show that the resistivity has a strong monotonically decreasing carrier density dependence at low temperature due to charged impurity scattering, and weak density dependence at high temperature due to gauge phonons. Away from charge neutrality, the resistivity increases with temperature, while it does the opposite close to the Dirac point. A nonmonotonic temperature dependence observed only at low temperature and carrier density is a signature of our theory that can be tested in experimentally available samples.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}