Crucial role of internal collective modes in underdoped cuprates

Mallik, Aabhaas V.; Yadav, Umesh K.; Medhi, Amal; Krishnamurthy, H. R.; Shenoy, Vijay B.

doi:10.1209/0295-5075/119/27004

Cited by 2 publications

(4 citation statements)

References 52 publications

(78 reference statements)

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“…This is in contrast with our results where the d-wave pairing gap 32 first increases and then attains a plateau at p ∼ 0.15. Interestingly, this behavior of the d-wave pairing gap on the overdoped side agrees qualitatively with cluster DMFT studies of a closely related Hubbard model 16 and a large-N theory that we had presented in a similar setting 30 . Most importantly, ARPES experiments on the cuprate Bi2212 10 and STM experiments on several cuprates 33 do find results consistent with such a behavior of the superconducting gap on the overdoped side.…”

Section: Discussionsupporting

confidence: 88%

“…Generically, this system has two phase modes and two amplitude modes corresponding to the complex valued fluctuations on the unique x and y bonds associated to each lattice site. On the overdoped side, where there is only d-wave pairing, the normal modes at q = 0 are given by the symmetric and anti-symmetric combinations of the phase (amplitude) modes: the symmetric phase mode (P s -mode, which is gapless in the absence of coupling to the electromagnetic gauge field), the anti-symmetric phase mode (P a -mode), the symmetric amplitude mode (A s -mode), and, the anti-symmetric amplitude mode (A a -mode) 30 . In the underdoped region where d + is pairs stabilize the P s -mode and A a -mode continue to be the normal modes in the q → 0 limit, while the P a -mode and A s -mode combine to give two new normal modes.…”

Section: Resultsmentioning

confidence: 99%

“…In the presence of fermionic pairing the system has soft collective modes in the underdoped regime (see e.g. 30 ) which, given that all the other fields are gapped, might actually be the most important contributor to fluctuations about the mean field theory. With this in mind, we choose to work with the following construction: 1) We set the gapped fields h and λ to their mean field value of zero, and assume that the fluctuations in the pairing channel do not affect their status.…”

Section: Modelmentioning

confidence: 99%

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Surprises in the t−J Model: Implications for Cuprates

et al. 2020

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The t-J model is a paradigmatic model for the study of strongly correlated electron systems. In particular, it has been argued that it is an appropriate model to describe the cuprate high-T c superconductors. It turns out that a comprehensive understanding of the gamut of physics encoded by the t-J model is still an open problem. In recent years some remarkable experiments on the cuprates, for example, discovery of nodeless superconductivity in underdoped samples (PNAS 109, 18332 (2012)), discovery of s-wave like gap in the pseudogap phase (Phys. Rev. Lett. 111, 107001 (2013)), and observation of polar Kerr effect (PKE) (Phys. Rev. Lett. 112, 047003 (2014)), have thrown up new challenges for this model. Here, we present results demonstrating that, within the slave-particle formulation of the t-J model, the d-wave superconductor is unstable at low doping to its own anti-symmetric phase mode fluctuations when the effect of fluctuations is treated selfconsistently. We then show that this instability gives way to a time reversal symmetry broken d + is-SC in the underdoped region which has superfluid stiffness consistent with Uemura relation, even with a large pair amplitude. We show that our results are consistent with existing experiments on cuprates and suggest that Josephson (SQUID interferometry) experiments can clearly distinguish the d+is-SC from a host of other possibilities alluded to be contributing to the physics of underdoped cuprates. We also comment on other theoretical studies vis-a-vis ours.The rich phase diagram of the copper oxide high-T c superconductors has been a major source of inspiration for several fields of inquiry in both experimental and theoretical condensed matter physics 1 . One of the important theoretical offshoots has been the extensive study of strongly correlated model systems like the t-J model 2-4 . While this model has been quite successful in explaining several features of the cuprate phase diagram 5-7 , a comprehensive understanding of the low temperature phase in the underdoped region is yet to be achieved 8,9 . Recent experiments like the observation of nodeless superconductivity in the underdoped cuprates 10,11 , and, clear signatures of breaking of time reversal symmetry 12,13 raise new challenges. A natural question one would like to ask is how much of this new physics is within the scope of the t-J model? The difficulty in addressing this question is two fold: 1) strong electron correlations, and, 2) increased importance of long-wavelength fluctuations because of low dimensionality. Numerical techniques like the Variational Monte Carlo (VMC) using projected mean field like wavefunctions 14,15 or Projected Entangled Pair States (PEPS) 9 do a good job of accounting for strong correlations, but miss out on the long-wavelength fluctuations because of finite size limitations. The cluster DMFT 16 studies on the related Hubbard model have similar issues.The slave-particle formulation of the t-J model 17,18 has an unique advantage in this respect. At the mean field level it agr...

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Section: Discussionsupporting

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Section: Modelmentioning

confidence: 99%

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Surprises in the t−J Model: Implications for Cuprates

et al. 2020

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“…A different route to realizing pseudo-LLs is to note that the onset of nematic order in a tetragonal d-wave SC spontaneously breaks the C 4 point group symmetry and will induce an extended s-wave component to the pair field 33 . There is evidence that the cuprates are proximate to such a QPT [46][47][48][49][50][51] , so that an edge-induced s-wave pairing component will exhibit slow spatial decay, leading naturally to a gap variation needed to form pseudo-LLs. Tuning near such a critical point, or using proximity effect coupling to an s-wave SC, can tune the decay length and amplitude of the s-wave gap, thus controlling the pseudo-magnetic field and permitting further experimental tests.…”

Section: B Proximity To Nematic Ordermentioning

confidence: 99%

Pseudo-Landau levels of Bogoliubov quasiparticles in strained nodal superconductors

et al. 2017

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Motivated by theory and experiments on strain induced pseudo-Landau levels (LLs) of Dirac fermions in graphene and topological materials, we consider its extension for Bogoliubov quasiparticles (QPs) in a nodal superconductor (SC). We show, using an effective low energy description and numerical lattice calculations for a d-wave SC, that a spatial variation of the electronic hopping amplitude or a spatially varying s-wave pairing component can act as a pseudo-magnetic field for the Bogoliubov QPs, leading to the formation of pseudo-LLs. We propose realizations of this phenomenon in the cuprate SCs, via strain engineering in films or nanowires, or s-wave proximity coupling in the vicinity of a nematic instability, and discuss its signatures in tunneling experiments. arXiv:1707.07683v4 [cond-mat.str-el]

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Crucial role of internal collective modes in underdoped cuprates

Cited by 2 publications

References 52 publications

Surprises in the t−J Model: Implications for Cuprates

Surprises in the t−J Model: Implications for Cuprates

Pseudo-Landau levels of Bogoliubov quasiparticles in strained nodal superconductors

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