Realizing infrared power-law liquids in the cuprates from unparticle interactions

Limtragool, Kridsanaphong; Setty, Chandan; Leong, Zhidong; Phillips, Philip

doi:10.1103/physrevb.94.235121

Cited by 11 publications

(13 citation statements)

References 25 publications

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“…In this paper, we show analytically that interactions between electrons and fermionic unparticles can reproduce the power-law liquid revealed in the cuprates by recent ARPES experiments 1 . This paper is a follow-up to our recent paper that focused on bosonic unparticles 22 .…”

Section: Introductionmentioning

confidence: 90%

Power-law liquid in cuprate superconductors from fermionic unparticles

et al. 2017

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Recent photoemission spectroscopy measurements [arXiv:1509.01611] on cuprate superconductors have inferred that over a wide range of doping, the imaginary part of the electron self-energy scales as $\Sigma^{\prime\prime}\sim(\omega^2+\pi^2T^2)^a$ with $a=1$ in the overdoped Fermi-liquid state and $a<0.5$ in the optimal to underdoped regime. We show that this non-Fermi-liquid scaling behavior can naturally be explained by the presence of a scale-invariant state of matter known as unparticles. We evaluate analytically the electron self-energy due to interactions with fermionic unparticles. We find that, in agreement with experiments, the imaginary part of the self-energy scales with respect to temperature and energy as $\Sigma^{\prime\prime}\sim T^{2+2\alpha}$ and $\omega^{2+2\alpha}$, where $\alpha$ is the anomalous dimension of the unparticle propagator. In addition, the calculated occupancy and susceptibility of fermionic unparticles, unlike those of normal fermions, have significant spectral weights even at high energies. This unconventional behavior is attributed to the branch cut in the unparticle propagator which broadens the unparticle spectral function over a wide energy range and non-trivially alters the scattering phase space by enhancing (suppressing) the intrinsic susceptibility at low energies for negative (positive) $\alpha$. Our work presents new evidence suggesting that unparticles might be important low-energy degrees of freedom in strongly coupled systems such as the cuprate superconductors.Comment: 10 pages, 7 figure

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Section: Introductionmentioning

confidence: 90%

Power-law liquid in cuprate superconductors from fermionic unparticles

et al. 2017

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“…Limtragool et al have introduced a phenomenological model to describe the power-law singular behavior of the strange metallic state of high-T c cuprate superconductors [41]. They attribute the power-law behavior to scale-invariant critical physics whose generation involves the coupling of electrons to bosonic unparticles which have scale-invariant features.…”

Section: Electrons Coupled To Unparticlesmentioning

confidence: 99%

“…In the Anderson's hidden Fermi liquid case [40,80], the Gutzwiller constraint on on-site double occupations is simplified by scattering effects of the background fluctuations, which leads to the singular propagation of the electrons with anomalous dimension. In the next example, unparticles with scale-invariant features were introduced to study the strange metallic state of the high-T c cuprate superconductors [41]. Their coupling to electrons was noted to lead to power-law non-Fermi liquid behavior.…”

Section: A Summarymentioning

confidence: 99%

Breakdown of Landau Fermi liquid theory: Restrictions on the degrees of freedom of quantum electrons

2017

Front. Phys.

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One challenge in contemporary condensed matter physics is to understand unconventional electronic physics beyond the paradigm of Landau Fermi-liquid theory. Here, we present a perspective that posits that most such examples of unconventional electronic physics stem from restrictions on the degrees of freedom of quantum electrons in Landau Fermi liquids. Since the degrees of freedom are deeply connected to the system's symmetries and topology, these restrictions can thus be realized by external constraints or by interaction-driven processes via the following mechanisms: (i) symmetry breaking, (ii) new emergent symmetries, and (iii) nontrivial topology. Various examples of unconventional electronic physics beyond the reach of traditional Landau Fermi liquid theory are extensively investigated from this point of view. Our perspective yields basic pathways to study the breakdown of Landau Fermi liquids and also provides a guiding principle in the search for novel electronic systems and devices.

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“…Specific to Eq. 1, since the scaling form is robust up to 0.1 eV and 250 K [1], we showed previously that such a behavior can originate from interactions between electrons and unparticles, a scale-invariant sector that naturally emerges due to strong correlations in the cuprates [12,13]. Originally proposed as a scale-invariant sector within the standard model [14], unparticles can arise in the cuprates because any nontrivial infrared dynamics in a strongly correlated electron system is controlled by a critical fixed point.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, a power-law liquid can be obtained from interactions between electrons and unparticles [12,13]. The propagator of fermionic unparticles can be written as G u (k, iω n ) = [iω n − u k ] −1+du , where d u is the anomalous dimension and u k is the energy spectrum of unparticles.…”

Section: Introductionmentioning

confidence: 99%

Scale invariance as the cause of the superconducting dome in the cuprates

et al. 2018

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Recent photoemission spectroscopy measurements (T. J. Reber et al., arXiv:1509.01611) of cuprate superconductors have inferred that the self-energy exhibits critical scaling over an extended doping regime, thereby calling into question the conventional wisdom that critical scaling exists only at isolated points. In particular, this new state of matter, dubbed a power-law liquid, has a selfenergy whose imaginary part scales as Σ ∼ (ω 2 + π 2 T 2 ) α , with α = 1 in the overdoped Fermi-liquid state and α ≤ 0.5 in the optimal to underdoped regime. Previously, we showed that this self-energy can arise from interactions between electrons and unparticles, a scale-invariant sector that naturally emerges from strong correlations. Here, taking the self-energy as a given, we first reconstruct the real part of the self-energy. We find that the resultant quasiparticle weight vanishes for any doping level less than optimal, implying an absence of particle-like excitations in the underdoped regime. Consequently, the Fermi velocity vanishes and the effective mass diverges for α ≤ 1 2 , in agreement with earlier experimental observations. We then use the self-energy to reconstruct the spectral function and compute the superconducting Tc within the BCS formalism. We find that the Tc has a dome-like structure, implying that broad scale invariance manifested in the form of a power-law liquid is the likely cause of the superconducting dome in the cuprates.

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Realizing infrared power-law liquids in the cuprates from unparticle interactions

Cited by 11 publications

References 25 publications

Power-law liquid in cuprate superconductors from fermionic unparticles

Power-law liquid in cuprate superconductors from fermionic unparticles

Breakdown of Landau Fermi liquid theory: Restrictions on the degrees of freedom of quantum electrons

Scale invariance as the cause of the superconducting dome in the cuprates

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