arXiv subjects

Asimkumar Ghosh

Publications and source records attributed to Asimkumar Ghosh.

4 recordsLinked to original sources

arXiv2004

Field-induced disorder in a gapped spin system with non-magnetic impurities

We study S=1/2 dimers which are weakly coupled by three-dimensional antiferromagnetic interactions J'. It is commonly known that doping with non-magnetic impurities immediately induces a long-range Neel order. We show that application of an external magnetic field H may drive the system back to a disordered phase. We discuss the zero temperature phase diagram in the (H,J') plane and we propose suggestions for experiments.

cond-mat.str-el↗

arXiv2001

Spin dynamics of a one-dimensional spin-1/2 fully anisotropic Ising-like antiferromagnet in a transverse magnetic field

We consider the one-dimensional Ising-like fully anisotropic S=1/2 Heisenberg antiferromagnetic Hamiltonian and study the dynamics of domain wall excitations in the presence of transverse magnetic field $h_x$. We obtain dynamical spin correlation functions along the magnetic field $S^{xx}(q,ω)$ and perpendicular to it $S^{yy}(q,ω)$. It is shown that the line shapes of $S^{xx}(q,ω)$ and $S^{yy}(q,ω)$ are purely symmetric at the zone-boundary. It is observed in $S^{yy}(q,ω)$ for $π/2<q<π$ that the spectral weight moves toward low energy side with the increase of $h_x$. This model is applicable to study the spin dynamics of CsCoCl$_3$ in the presence of weak interchain interactions.

cond-mat.str-el↗

arXiv1997

Exact ground and excited states of frustrated antiferromagnets on the CaV_4O_9 lattice

The experimental observation of a spin-gap in the antiferromagnetic spin-1/2 compound $CaV_4O_9$ has been attributed to the formation of a plaquette resonating-valence-bond (PRVB) state in the underlying 1/5-depleted square lattice. We construct a spin-1/2 model on the 1/5-depleted lattice for which the PRVB state can be shown to be the exact ground state in a particular parameter regime. In a subspace of this parameter regime, the first excited state can be calculated exactly. In a different parameter regime, the dimer state is shown to be the exact ground state.

cond-mat.str-el↗

arXiv1996

Antiferromagnetic Spin Ladders with Odd and Even number of Chains

We construct frustrated antiferromagnetic spin ladders with m chains for which the exact ground state can be determined in a particular parameter regime. The excitation spectrum is shown rigorously to be gapless ( with gap ) for odd ( even ) m. In a general parameter regime, the four-chain and periodic ladders are studied using a mean-field theory based on the bond operator formalism for spin $S=1/2$. The excitation spectrum and the spin-gap are calculated in both the cases. The spin-gap of the frustrated ladder system has a larger magnitude than in the case of non-frustrated ladders. For the frustrated periodic ladder, the spin-gap vanishes at a critical value of the interladder coupling strength which is larger than the critical value in the case of non-frustrated periodic ladder.

cond-mat.str-el↗