arXiv subjects

Shri Hari Soundararaj

Publications and source records attributed to Shri Hari Soundararaj.

3 recordsLinked to original sources

arXiv2024

Quantum MASALA: Quantum MAterialS Ab initio eLectronic-structure pAckage

We present Quantum MASALA, a compact package that implements different electronic structure methods in Python using the plane-wave basis. Within just 8100 lines of pure Python code, we have implemented Density Functional Theory (DFT), Time-dependent Density Functional Theory (TD-DFT) and the GW Method. The program can run across multiple processors and in Graphical Processing Units (GPU) with the help of easily accessible Python libraries. With Quantum ESPRESSO and BerkeleyGW input interfaces implemented, it can also be used as a substitute for small and medium scale calculations, making it a perfect learning tool for ab initio methods. The package is aimed to provide a framework with its modular and simple code design to rapidly build and test new methods for first-principles calculation.

cond-mat.mtrl-sci↗

arXiv2024

Topological magnonic properties of an antiferromagnetic chain

The magnonic excitations of a dimerized, one-dimensional, antiferromagnetic chain can be trivial or topological depending on the signs and magnitudes of the alternating exchange couplings and the anisotropy. The topological phase that occurs when the signs of the two different exchange couplings alternate is qualitatively different from that of the Su-Schrieffer-Heeger model. A material that may exhibit these properties is the quasi-one-dimensional material MoI$_3$ that consists of dimerized chains weakly coupled to adjacent chains. The magnetic ground state and its excitations are analyzed both analytically and numerically using exchange and anisotropy parameters extracted from density functional theory calculations.

cond-mat.mes-hall↗

arXiv2024

Engineering ultra-strong electron-phonon coupling and nonclassical electron transport in crystalline gold with nanoscale interfaces

Electrical resistivity in good metals, particularly noble metals such as gold (Au), silver (Ag), or copper, increases linearly with temperature ($T$) for $T > Θ_{\mathrm{D}}$, where $Θ_{\mathrm{D}}$ is the Debye temperature. This is because the coupling ($λ$) between the electrons and the lattice vibrations, or phonons, in these metals is rather weak with $λ\sim 0.1-0.2$, and a perturbative analysis suffices to explain the $T$-linear electron-phonon scattering rate. In this work, we outline a new nanostructuring strategy of crystalline Au where this foundational concept of metallic transport breaks down. We show that by embedding a distributed network of ultra-small Ag nanoparticles (AgNPs) of radius $\sim1-2$ nm inside a crystalline Au shell, an unprecedented enhancement in the electron-phonon interaction, with $λ$ as high as $\approx 20$, can be achieved. This is over hundred times that of bare Au or Ag, and ten times larger than any known metal. With increasing AgNP density, the electrical resistivity deviates from $T$-linearity, and approaches a saturation to the Mott-Ioffe-Regel scale $ρ_{\mathrm{MIR}}\sim h a /e^2$ for both disorder ($T\to 0$) and phonon ($T \gg Θ_{\mathrm{D}}$)-dependent components of resistivity (here, $a=0.3$~nm, is the lattice constant of Au). This giant electron-phonon interaction, which we suggest arises from the coulomb interaction-induced coupling of conduction electrons to the localized phonon modes at the buried Au-Ag hetero-interfaces, allows experimental access to a regime of nonclassical metallic transport that has never been probed before.

cond-mat.mes-hall↗