Superconducting fluctuations in organic molecular metals enhanced by Mott criticality

Nam, Moon S.; Meźière, Cécile; Batail, Patrick; Zorina, Leokadiya V.; Simonov, Sergey V.; Ardavan, Arzhang

doi:10.1038/srep03390

Cited by 24 publications

(19 citation statements)

References 43 publications

(84 reference statements)

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“…Specifically, in κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Cl 1−x Br x , with x = 0.73, a Drude-like peak is seen to emerge at T 50K [32]. At precisely these temperatures a substantial, magnetic field dependent Nernst effect is also observed [12]. While this peak has been interpreted in terms of 'coherent quasiparticles', the evidence for superconducting phase fluctuations over the same temperature range may warrant a new look.…”

Section: Experimental Motivationmentioning

confidence: 91%

“…Phase fluctuations are expected to be generically important in systems with a small superfluid density such as organic and cuprate superconductors [7,8,9]. Relatively inefficient Coulomb screening can increase the importance of quantum effects [10], as can proximity to a Mott transition [11,12]. The most dramatic and established appearance of quantum phase fluctuations, however, is in disordered thin films which we now discuss in more detail.…”

Section: Experimental Motivationmentioning

confidence: 98%

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Hydrodynamic theory of quantum fluctuating superconductivity

et al. 2016

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A hydrodynamic theory of transport in quantum mechanically phase-disordered superconductors is possible when supercurrent relaxation can be treated as a slow process.We obtain general results for the frequency-dependent conductivity of such a regime.With time-reversal invariance, the conductivity is characterized by a Drude-like peak, with width given by the supercurrent relaxation rate. Using the memory matrix formalism, we obtain a formula for this width (and hence also the dc resistivity) when the supercurrent is relaxed by short range density-density interactions. This leads to a new -effective field theoretic and fully quantum -derivation of a classic result on flux flow resistance. With strong breaking of time-reversal invariance, the optical conductivity exhibits what we call a 'hydrodynamic supercyclotron' resonance. We obtain the frequency and decay rate of this resonance for the case of supercurrent relaxation due to an emergent Chern-Simons gauge field. The supercurrent decay rate in this 'topologically ordered superfluid vortex liquid' is determined by the conductivities of the normal fluid component, rather than the vortex core.

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Section: Experimental Motivationmentioning

confidence: 91%

Section: Experimental Motivationmentioning

confidence: 98%

Hydrodynamic theory of quantum fluctuating superconductivity

et al. 2016

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“…We here recall H c2 (0) of other families of high- T c or strongly correlated superconductors, i.e., cuprates, organic κ-(ET) 2 X, and pnictides 24 27 28 29 30 31 , having a dome-like SC phase and a proximate antiferromagnetic phase. In Fig.…”

Section: Discussionmentioning

confidence: 99%

Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors

et al. 2017

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Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (Tc) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field Hc2 of the fulleride superconductors reaches values as high as ∼90 T—the highest among cubic crystals. This is accompanied by a crossover from weak- to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn–Teller effect as the Mott transition is approached. These results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-Tc and high-Hc2.

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“…3(a)) and Cu[N(CN) 2 ]Br (point C) in ambient pressure [45] and from the magnetization results of Cu(NCS) 2 on the SFD in applied pressure [46]. It also shows the Nernst onset temperature T ner in X = Cu[N(CN) 2 ](Br,I) [47] for Br 100% (C), 80 % (B) and 73% (A) samples. Although nearly all the "underdoped" region is masked by the magnetic order, T ner lies close to TBEC near the boundary to the magnetic order, and the Nernst effect dies away rapidly with increasing (chemical) pressure.…”

Section: (D) Phase Diagrams Of Bedt and A 3 C 60 Systems With Photo-ementioning

confidence: 96%

Dynamic superconductivity responses in photoexcited optical conductivity and Nernst effect

Uemura

2019

Phys. Rev. Materials

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High-T c cuprate, alkali-doped C 60 and several other unconventional superconductors have very high transition temperatures T c with respect to the energy scale of superconducting (SC) charges inferred from the superfluid density (SFD). The observed linear relationship between T c and the SFD can hardly be expected in BCS superconductors while being reminiscent of Bose Einstein Condensation of pre-formed bosonic charges. As additional non-BCS like behaviors, responses similar to those in the bulk SC states have been observed at temperatures well above T c in the vortex-like Nernst effect, diamagnetic susceptibility, and transient optical conductivity in recent photo-excited pump-probe measurements. In this paper, we propose a coherent picture based on equilibrium and transient SFD to understand these unconventional behaviors in cuprates, K 3 C 60 , and organic superconductors. This picture assumes: (1) Dynamic SC responses in the Nernst and photo-induced measurements emerge at the formation of the local phase coherence (LPC) among wave functions of pre-formed bosonic pairs. (2) Its onset temperature T LPC is distinct from and lower than the boson formation temperature often denoted as the "pseudo-gap temperature" T*, as T LPC is determined by the many-body boson density while T* represents attractive interaction between two fermions. (3) The bulk superconducting T c , signaling global phase coherence, is significantly reduced from T LPC , due to the competition between the SC and antiferromagnetic (AF) order. (4) The inelastic magnetic resonance mode (MRM) controls T c in the SC-AF competition. (5) The transient optical responses can be attributed to a change of the balance between the competing SC and AF orders caused by photo excitation. The assumptions (1) and (2) explain the relationship between T c and the transient SFD in photo excited studies and equilibrium SFD in Nernst effect. (3) and (4) are inferred from the linear dependence of T c on the MRM energy. (4) and (5) are consistent with the behaviors of the 400 cm -1 optical responses in equilibrium and photo-excited studies and temperature dependence of the intensity of this optical mode and the MRM. Unlike previous phase-fluctuation pictures which expect dynamic responses between T* and T c , the present picture involving competing order indicates that dynamic SC responses are seen between T LPC and T c .

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Superconducting fluctuations in organic molecular metals enhanced by Mott criticality

Cited by 24 publications

References 43 publications

Hydrodynamic theory of quantum fluctuating superconductivity

Hydrodynamic theory of quantum fluctuating superconductivity

Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors

Dynamic superconductivity responses in photoexcited optical conductivity and Nernst effect

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