The ground state of a charged Bose gas is studied throughout a large range of densities in a self-consistent-field approximation formalism which includes the short-range correlations between bosons through a local-field correction. Numerical self-consistent calculations have been carried out in order to determine the static structure factor $S(\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}})$. Hence, from $S(\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}})$ we have obtained the pair-correlation functions, the ground-state energy which essentially is the correlation energy, the pressure of the gas, and, from Feynman's relation, the energy spectrum of elementary excitations. The response of the system to a static impurity charge has also been investigated. In the high-density limit our calculations show the same results as those given by Bogoliubov's perturbation theory. In the intermediate-density region, corresponding to the strongly coupled system, our results are in very good agreement with recent calculations based on the hypernetted-chain integral equation as well as Monte Carlo computations.The ground state of a charged Bose gas is studied throughout a large range of densities in a self-consistent-field approximation formalism which includes the short-range correlations between bosons through a local-field correction. Numerical self-consistent calculations have been carried out in order to determine the static structure factor $S(\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}})$. Hence, from $S(\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}})$ we have obtained the pair-correlation functions, the ground-state energy which essentially is the correlation energy, the pressure of the gas, and, from Feynman's relation, the energy spectrum of elementary excitations. The response of the system to a static impurity charge has also been investigated. In the high-density limit our calculations show the same results as those given by Bogoliubov's perturbation theory. In the intermediate-density region, corresponding to the strongly coupled system, our results are in very good agreement with recent calculations based on the hypernetted-chain integral equation as well as Monte Carlo computations.

Physical Review ANov 1, 198226 citations

Excitation spectrum of a condensed bose system

P. D�rre

The European Physical Journal BMar 1, 19801 citation

Spectrum of elementary and collective excitations in the dimerized S=1/2 Heisenberg chain with frustration

Pavel V. Shevchenko, Valeri N. Kotov, Oleg P. Sushkov

We have studied the low-energy excitation spectrum of a dimerized and frustrated antiferromagnetic Heisenberg chain. We use an analytic approach, based on a description of the excitations as triplets above a strong-coupling singlet ground state. The quasiparticle spectrum is calculated by treating the excitations as a dilute Bose gas with infinite on-site repulsion. Additional singlet $(S=0)$ and triplet $(S=1)$ modes are found as two-particle bound states of the elementary triplets. We have also calculated the contributions of the elementary and collective excitations into the spin structure factor. Our results are in excellent agreement with exact diagonalizations and dimer series expansions data as long as the dimerization parameter \ensuremath{\delta} is not too small $(\ensuremath{\delta}>0.1),$ i.e., while the elementary triplets can be treated as localized objects.We have studied the low-energy excitation spectrum of a dimerized and frustrated antiferromagnetic Heisenberg chain. We use an analytic approach, based on a description of the excitations as triplets above a strong-coupling singlet ground state. The quasiparticle spectrum is calculated by treating the excitations as a dilute Bose gas with infinite on-site repulsion. Additional singlet $(S=0)$ and triplet $(S=1)$ modes are found as two-particle bound states of the elementary triplets. We have also calculated the contributions of the elementary and collective excitations into the spin structure factor. Our results are in excellent agreement with exact diagonalizations and dimer series expansions data as long as the dimerization parameter \ensuremath{\delta} is not too small $(\ensuremath{\delta}>0.1),$ i.e., while the elementary triplets can be treated as localized objects.

arXiv:cond-mat/9901302Physical review. B, Condensed matterAug 1, 199923 citations

Excitation picture of an interacting Bose gas

M. Kira

arXiv:1407.4920Annals of PhysicsSep 6, 201415 citations

Path-integral approach to Cooper pairs and charged bosons

A. S. Alexandrov, S. G. Rubin

With the functional-integral technique, equations for the excitation spectrum of fermions with an arbitrary strong attraction are obtained. The evolution of the BCS excitation spectrum in the weak-coupling regime to the excitations of a Bose gas in the strong-coupling regime is discussed. To obtain the Bogolubov sound in the strong-coupling regime, four-particle correlations are taken into account. The functional integration allows a discussion of the excitations at a finite temperature and a controlled treatment of the problem of maximum attainable ${\mathit{T}}_{\mathit{c}}$ .With the functional-integral technique, equations for the excitation spectrum of fermions with an arbitrary strong attraction are obtained. The evolution of the BCS excitation spectrum in the weak-coupling regime to the excitations of a Bose gas in the strong-coupling regime is discussed. To obtain the Bogolubov sound in the strong-coupling regime, four-particle correlations are taken into account. The functional integration allows a discussion of the excitations at a finite temperature and a controlled treatment of the problem of maximum attainable ${\mathit{T}}_{\mathit{c}}$.

Physical review. B, Condensed matterMar 1, 199313 citations

(S=0)

and triplet

(S=1)

modes are found as two-particle bound states of the elementary triplets. We have also calculated the contributions of the elementary and collective excitations into the spin structure factor. Our results are in excellent agreement with exact diagonalizations and dimer series expansions data as long as the dimerization parameter \ensuremath{\delta} is not too small $(\ensuremath{\delta}>0.1),$ i.e., while the elementary triplets can be treated as localized objects.

{\mathit{T}}_{\mathit{c}}