arXiv subjects

P K Biswas

Publications and source records attributed to P K Biswas.

4 recordsLinked to original sources

arXiv2021

$μ$SR study of unconventional pairing symmetry in the quasi-1D Na$_2$Cr$_3$As$_3$ superconductor

We report the finding of a novel pairing state in a newly discovered superconductor Na$_2$Cr$_3$As$_3$. This material has a noncentrosymmetric quasi-one-dimensional crystal structure and is superconducting at $T_{\mathrm{C}}\sim$ 8.0 K. We find that the magnetic penetration depth data suggests the presence of a nodal line $p_z$-wave pairing state with zero magnetic moment using transverse-field muon-spin rotation (TF-$μ$SR) measurements. The nodal gap observed in Na$_2$Cr$_3$As$_3$ compound is consistent with that observed in isostructural (K,Cs)$_2$Cr$_3$As$_3$ compounds using TF-$μ$SR measurements. The observed pairing state is consistent with a three-band model spin-fluctuation calculation, which reveals the $S_z=0$ spin-triplet pairing state with the $\sin k_z$ pairing symmetry. The long-sought search for chiral superconductivity with topological applications could be aided by such a novel triplet $S_z=0$ $p$-wave pairing state.

cond-mat.supr-con↗

arXiv2002

A new ab initio method of calculating $Z_{eff}$ and positron annihilation rates using coupled-channel T-matrix amplitudes

A new {\it ab initio} theoretical formulation to calculate $Z_{eff}$ and hence the positron annihilation rates is presented using the on-shell and half-offshell T-matrix scattering amplitudes without any explicit use of the scattering wave function. The formulation is exact and universal, as long as the dynamics of the system can be described by a Lippmann-Schwinger type equation. It could serve as an effective tool as all the $T-$, $K-$, and $S-$matrix formulations, yield directly the scattering amplitudes; not the wave function. We also present a basic numerical test of the formulation.

physics.atom-ph↗

arXiv2001

Scattering of positronium from singly ionized helium and appearing resonances

The coupled-channel model [Phys. Rev. A {\bf 59}, 363 (1999)] that yields converged low-energy phase shifts, and exact binding and resonance features in Ps-H [Phys. Rev. A {\bf 59}, 2058 (1999)] is applied to study Ps-He$^+$ scattering. Similar to PsH, resonances appear in the S-, P-, D-, etc partial waves in the Ps-He$^+$ system but in both the singlet and triplet scattering channels. The latter signifies possible Rydberg states of $e^+$ around singlet and triplet helium. The S-wave singlet resonance at 2.79 eV agrees to that predicted earlier in $e^+$-He entrance channel (energy difference 16.64 eV) at 19.27 eV [Chem. Phys. Lett. {\bf 262}, 460 (1996)].

physics.atom-ph↗

arXiv2001

Effect of H$^-$ ion formation on Positronium-Hydrogen elastic scattering

Effect of charge-transfer recombination for positronium (Ps) scattering is studied on Ps-H system using coupled-channel formalism considering a new rearrangement channel Ps+H --> e^+ + H^- and exchange. The correlation and continuum effects introduced by this charge-transfer channel result to substantial convergence to the low energy scattering parameters. Effects on scattering length, PsH binding energy, and low-energy (0-10 eV) phase-shifts and cross sections are evaluated and H$^-$ formation cross sections are reported from above the threshold (6.438 eV) to 100 eV.

physics.atom-ph↗