Dimensionality-induced BCS-BEC crossover in layered superconductors

Adachi, Kyosuke; Ikeda, Ryusuke

doi:10.1103/physrevb.98.184502

Cited by 5 publications

(6 citation statements)

References 29 publications

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“…To explain physical meanings of the definitions of T * and T c , it is convenient to consider the opposite limit to the weak-coupling BCS one in which T * and T c take almost the same value. In this strong-coupling limit (U/t → ∞), we can show that T * ∝ |µ| ∝ U ∝ E b , where E b is the two-particle binding energy [25]; therefore, T * can be interpreted as the pair-formation (or pairbreaking) temperature. Actually, regardless of the interaction strength U , T * is of the same order of magnitude as the zero-temperature excitation energy gap E gap , which can be interpreted as a typical energy scale to break an electron pair (see Appendix A); thus, T * can be interpreted as the pair-formation temperature.…”

Section: Zero-field Pair-formation and Pair-condensation Temperaturesmentioning

confidence: 88%

“…V, U = 2.57t (green dotted line) and 5.14t (yellow dotted line), are also shown. also show with a grey dotted line the threshold value U = U 0 8.14t for the formation of a two-particle bound state [21,25,26]. Note that the BCS-BEC crossover occurs close to U 0 .…”

Section: Zero-field Pair-formation and Pair-condensation Temperaturesmentioning

confidence: 96%

“…is already taken into account by properly choosing the origin of energy; therefore we do not explicitly consider Σ (H) [20,25].…”

Section: Zero-field Pair-formation and Pair-condensation Temperaturesmentioning

confidence: 99%

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Stabilization of the vortex-liquid state by strong pairing interaction

Adachi

Ikeda

2019

Phys. Rev. B

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We theoretically investigate qualitative features of the field-temperature (H-T ) phase diagram of superconductors with strong attractive interaction lying in the BCS-BEC crossover regime. Starting with a simple attractive Hubbard model, we estimate three kinds of characteristic fields, i.e., the pair-formation field H * , the vortex-liquid-formation field Hc2, and the vortex-lattice-formation field H melt . The region between Hc2 and H melt , as well as that between Hc2 and H * , is found to be enlarged as the interaction is stronger. In other words, a strong attractive interaction can stabilize both the vortex-liquid and preformed-pair regions. We also point out the expected particle-density dependence of the H-T phase diagram.

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Section: Zero-field Pair-formation and Pair-condensation Temperaturesmentioning

confidence: 88%

Section: Zero-field Pair-formation and Pair-condensation Temperaturesmentioning

confidence: 96%

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Stabilization of the vortex-liquid state by strong pairing interaction

Adachi

Ikeda

2019

Phys. Rev. B

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“…where p and q correspond to the momentum of impurity and hole respectively, ω and Ω correspond to the frequency of impurity and hole respectively. For pairing mechanism, this expression is definitely important, e.g., for the pairing instability [57,37,58,59] and the resonantly enhanced correlation, and its real part and imaginary part are easy to obtained by firstly replacing the imaginary frequencies in denominator with the analytical continuation and then using the Dirac identity (for retarded functions) lim η→0…”

Section: Pair Propagator and Relaxation Time At Finite Temperaturementioning

confidence: 99%

Attractive polaron formed in doped nonchiral/chiral parabolic system within ladder approximation

2020

Physica B: Condensed Matter

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We investigate the properties of attractive polaron formed by a single impurity dressed with the particle-hole excitations in a three-dimensional (3D) doped (extrinsic) parabolic system. Base on the single particle-hole variational ansatz, we study the pair propagator, self-energy, and the non-self-consistent medium T -matrix. The non-self-consistent T -matrix discussed in this paper contains only the open channel since we don't consider the shift of center-of-mass due to the resonance (e.g., induced by the magnetic field). Besides, since we focus on the low-density regime of the majority particles, the effective Fermi wave vector is small. The scattering form factor is discussed in detail for the chiral case and compared to the non-chiral one. The effects of the bare coupling strength, which is momentum-cutoff-dependent, are also discussed. We found that the pair propagator and the related quantities, like the self-energy, spectral function, induced effective mass, and residue (spectral weight), all exhibit different features in the low-momentum regime and the high one, which also related to the polaronic instabilities as well as the many-body fluctuation and nonadiabatic/adiabatic dynamics. The pair-propagator and the energy relaxation time at finite temperature are also explored.

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“…If the interspecies interaction changes to zero, the full polarization becomes simply the overlap of the impurity and majority particle, and we can expect that the polarization has two distinct peaks in such case, contributed by the two components respectively. Further, when consider the perturbation effect, the Hartree term with bare attractive interaction should be contained in the self-energy [51].…”

Section: Coulomb Interaction and Induced Self-energymentioning

confidence: 99%

Electronic properties and polaronic dynamics of semi-Dirac system within Ladder approximation

2020

Phys. Scr.

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We investigate the electronic properties of the semi-Dirac system and its polaronic dynamics when coupled with a fermi bath with quadratic dispersion. The electronic anisotropic transport properties and the semiclassical dynamics of the semi-Dirac system are studied, including the density-of-states, conductivity, transport relaxation rate, specific heat, electrical current denity, and free energy. The attractive polaron formed as the semi-Dirac impurity dressed with the particle-hole excitations in a two-dimensional system are studied both analytically and numerically. The pair propagator, self-energy, spectral function are being detailly calculated and discussed. The method of medium T -matrix approximation (non-self-consistent), which equivalent to the partially dressed interaction vertex by summing over all ladder diagrams, is applied, and compared with some other methods (for many-body problem), like the leading-order 1/N expansion (GW approximation), Hartree-Fock theory, and the Nozieres-Schmitt-Rink theory. Since we foucs on the weak-coupling region, the mean-field approximation is also applicable. The polaron properties is related to the anisotropic effective masses of the semi-Dirac system. That's in contrast to the polarons formed in the surface of normal Dirac systems which has an isotropic dispersion, since the anisotropic dispersion of the semi-Dirac systems results in anisotropic effective mass and anisotropic charge carrier transport. Besides, the symmetry between electron and hole is also broken since the effective masses of the electron and hole are different, which are affected by the polaronic effect when the semi-Dirac material is deposited on a polar substrate, like hBN. The self-localization, short-range potential, and experimental methods as well as the possible formation of the bose polaron on the surface of semi-Dirac system are also discussed in the end. Our results are useful also for the investigation of two/three-dimensional bosonic polaron as well as the polarons in other solid state systems, like the magnetic matter or the topological systems. *

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Dimensionality-induced BCS-BEC crossover in layered superconductors

Cited by 5 publications

References 29 publications

Stabilization of the vortex-liquid state by strong pairing interaction

Stabilization of the vortex-liquid state by strong pairing interaction

Attractive polaron formed in doped nonchiral/chiral parabolic system within ladder approximation

Electronic properties and polaronic dynamics of semi-Dirac system within Ladder approximation

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