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1.
Nature ; 601(7894): 562-567, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-35082417

RESUMO

In conventional superconductors, the phase transition into a zero-resistance and perfectly diamagnetic state is accompanied by a jump in the specific heat and the opening of a spectral gap1. In the high-transition-temperature (high-Tc) cuprates, although the transport, magnetic and thermodynamic signatures of Tc have been known since the 1980s2, the spectroscopic singularity associated with the transition remains unknown. Here we resolve this long-standing puzzle with a high-precision angle-resolved photoemission spectroscopy (ARPES) study on overdoped (Bi,Pb)2Sr2CaCu2O8+δ (Bi2212). We first probe the momentum-resolved electronic specific heat via spectroscopy and reproduce the specific heat peak at Tc, completing the missing link for a holistic description of superconductivity. Then, by studying the full momentum, energy and temperature evolution of the spectra, we reveal that this thermodynamic anomaly arises from the singular growth of in-gap spectral intensity across Tc. Furthermore, we observe that the temperature evolution of in-gap intensity is highly anisotropic in the momentum space, and the gap itself obeys both the d-wave functional form and particle-hole symmetry. These findings support the scenario that the superconducting transition is driven by phase fluctuations. They also serve as an anchor point for understanding the Fermi arc and pseudogap phenomena in underdoped cuprates.

2.
Science ; 366(6469): 1099-1102, 2019 11 29.
Artigo em Inglês | MEDLINE | ID: mdl-31780552

RESUMO

In normal metals, macroscopic properties are understood using the concept of quasiparticles. In the cuprate high-temperature superconductors, the metallic state above the highest transition temperature is anomalous and is known as the "strange metal." We studied this state using angle-resolved photoemission spectroscopy. With increasing doping across a temperature-independent critical value p c ~ 0.19, we observed that near the Brillouin zone boundary, the strange metal, characterized by an incoherent spectral function, abruptly reconstructs into a more conventional metal with quasiparticles. Above the temperature of superconducting fluctuations, we found that the pseudogap also discontinuously collapses at the very same value of p c These observations suggest that the incoherent strange metal is a distinct state and a prerequisite for the pseudogap; such findings are incompatible with existing pseudogap quantum critical point scenarios.

3.
Phys Rev Lett ; 119(18): 181601, 2017 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-29219557

RESUMO

We present a minimal bottom-up extension of the Chern-Simons bulk action for holographic translational symmetry breaking that naturally gives rise to pair density waves. We construct stationary inhomogeneous black hole solutions in which both the U(1) symmetry and spatially translational symmetry are spontaneously broken at a finite temperature and charge density. This novel solution provides a dual description of a superconducting phase intertwined with charge, current, and parity orders.

4.
Sci Rep ; 7(1): 6118, 2017 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-28733638

RESUMO

The ultimate consequence of quantum many-body physics is that even the air we breathe is governed by strictly unitary time evolution. The reason that we perceive it nonetheless as a completely classical high temperature gas is due to the incapacity of our measurement machines to keep track of the dense many-body entanglement of the gas molecules. The question thus arises whether there are instances where the quantum time evolution of a macroscopic system is qualitatively different from the equivalent classical system? Here we study this question through the expansion of noninteracting atomic clouds. While in many cases the full quantum dynamics is indeed indistinguishable from classical ballistic motion, we do find a notable exception. The subtle quantum correlations in a Bose gas approaching the condensation temperature appear to affect the expansion of the cloud, as if the system has turned into a diffusive collision-full classical system.

5.
Phys Rev E ; 95(2-1): 022704, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28297940

RESUMO

The paradigm of spontaneous symmetry breaking encompasses the breaking of the rotational symmetries O(3) of isotropic space to a discrete subgroup, i.e., a three-dimensional point group. The subgroups form a rich hierarchy and allow for many different phases of matter with orientational order. Such spontaneous symmetry breaking occurs in nematic liquid crystals, and a highlight of such anisotropic liquids is the uniaxial and biaxial nematics. Generalizing the familiar uniaxial and biaxial nematics to phases characterized by an arbitrary point-group symmetry, referred to as generalized nematics, leads to a large hierarchy of phases and possible orientational phase transitions. We discuss how a particular class of nematic phase transitions related to axial point groups can be efficiently captured within a recently proposed gauge theoretical formulation of generalized nematics [K. Liu, J. Nissinen, R.-J. Slager, K. Wu, and J. Zaanen, Phys. Rev. X 6, 041025 (2016)2160-330810.1103/PhysRevX.6.041025]. These transitions can be introduced in the model by considering anisotropic couplings that do not break any additional symmetries. By and large this generalizes the well-known uniaxial-biaxial nematic phase transition to any arbitrary axial point group in three dimensions. We find in particular that the generalized axial transitions are distinguished by two types of phase diagrams with intermediate vestigial orientational phases and that the window of the vestigial phase is intimately related to the amount of symmetry of the defining point group due to inherently growing fluctuations of the order parameter. This might explain the stability of the observed uniaxial-biaxial phases as compared to the yet to be observed other possible forms of generalized nematic order with higher point-group symmetries.

6.
Phys Rev E ; 94(2-1): 022701, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27627370

RESUMO

The concept of symmetry breaking has been a propelling force in understanding phases of matter. While rotational-symmetry breaking is one of the most prevalent examples, the rich landscape of orientational orders breaking the rotational symmetries of isotropic space, i.e., O(3), to a three-dimensional point group remain largely unexplored, apart from simple examples such as ferromagnetic or uniaxial nematic ordering. Here we provide an explicit construction, utilizing a recently introduced gauge-theoretical framework, to address the three-dimensional point-group-symmetric orientational orders on a general footing. This unified approach allows us to enlist order parameter tensors for all three-dimensional point groups. By construction, these tensor order parameters are the minimal set of simplest tensors allowed by the symmetries that uniquely characterize the orientational order. We explicitly give these for the point groups {C_{n},D_{n},T,O,I}⊂SO(3) and {C_{nv},S_{2n},C_{nh},D_{nh},D_{nd},T_{h},T_{d},O_{h},I_{h}}⊂O(3) for n,2n∈{1,2,3,4,6,∞}. This central result may be perceived as a road map for identifying exotic orientational orders that may become more and more in reach in view of rapid experimental progress in, e.g., nanocolloidal systems and novel magnets.

7.
Nature ; 536(7616): 282-3, 2016 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-27535532

Assuntos
Elétrons , Física
8.
Science ; 351(6277): 1026-7, 2016 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-26941303
9.
Nature ; 515(7526): 205-6, 2014 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-25391957
10.
Artigo em Inglês | MEDLINE | ID: mdl-24125227

RESUMO

Usually complex charge ordering phenomena arise due to competing interactions. We have studied how such ordered patterns emerge from the frustration of a long-ranged interaction on a lattice. Using the lattice gas model on a square lattice with fixed particle density, we have identified several interesting phases, such as a generalization of Wigner crystals at low particle densities and stripe phases at densities between ρ=1/3 and 1/2. These stripes act as domain walls in the checkerboard phase present at half-filling. The phases are characterized at zero temperatures using numerical simulations, and mean field theory is used to construct a finite temperature phase diagram.

11.
Nature ; 498(7452): 41-2, 2013 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-23739419
12.
Photochem Photobiol ; 89(2): 259-73, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23216105

RESUMO

The photoreceptor phytochrome switches photochromically between two thermally stable states called Pr and Pfr. Here, we summarize recent solid-state magic-angle spinning (MAS) NMR work on this conversion process and interpret the functional mechanism in terms of a nano-machine. The process is initiated by a double-bond photoisomerization of the open-chain tetrapyrrole chromophore at the methine bridge connecting pyrrole rings C and D. The Pr-state chromophore and its surrounding pocket in canonical cyanobacterial and plant phytochromes has significantly less order, tends to form isoforms and is soft. Conversely, Pfr shows significantly harder chromophore-protein interactions, a well-defined protonic and charge distribution with a clear classical counterion for the positively charged tetrapyrrole system. The soft-to-hard/disorder-to-order transition involves the chromophore and its protein surroundings within a sphere of at least 5.5 Å. The relevance of this collective event for signaling is discussed. Measurement of the intermediates during the Pfr → Pr back-reaction provides insight into the well-adjusted mechanics of a two-step transformation. As both Pr → Pfr and Pfr → Pr reaction pathways are different in ground and excited states, a photochemically controlled hyper-landscape is proposed allowing for ratchet-type reaction dynamics regulating signaling activity.


Assuntos
Proteínas de Bactérias/química , Fitocromo/química , Proteínas de Plantas/química , Prótons , Tetrapirróis/química , Cianobactérias/química , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Plantas/química , Conformação Proteica , Isoformas de Proteínas/química , Transdução de Sinais , Eletricidade Estática
13.
Phys Rev Lett ; 108(10): 106403, 2012 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-22463432

RESUMO

We show that the π flux and the dislocation represent topological observables that probe two-dimensional topological order through binding of the zero-energy modes. We analytically demonstrate that π flux hosts a Kramers pair of zero modes in the topological Γ (Berry phase Skyrmion at the zero momentum) and M (Berry phase Skyrmion at a finite momentum) phases of the M-B model introduced for the HgTe quantum spin Hall insulator. Furthermore, we analytically show that the dislocation acts as a π flux, but only so in the M phase. Our numerical analysis confirms this through a Kramers pair of zero modes bound to a dislocation appearing in the M phase only, and further demonstrates the robustness of the modes to disorder and the Rashba coupling. Finally, we conjecture that by studying the zero modes bound to dislocations all translationally distinguishable two-dimensional topological band insulators can be classified.

14.
Biochemistry ; 50(51): 10987-9, 2011 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-22124256

RESUMO

The red/far-red-sensing biological photoreceptor phytochrome is a paradigmatic two-state signaling system. The two thermally stable states are interconverted via a photoreaction of the covalently bound tetrapyrrole chromophore. Applying recently developed solid-state nuclear magnetic resonance, we study both the chromophore and its protein pocket in the Pr (red-absorbing) and Pfr (far-red-absorbing) states. The observations show that the phototransformation combines local chemical reactions with a mesoscopic transition of order. Both the chromophore and its binding pocket are quasi-liquid and disordered in Pr, yet quasi-solid and ordered in Pfr. Possible biochemical implications are discussed.


Assuntos
Fotorreceptores de Plantas/química , Fitocromo/química , Proteínas de Bactérias/química , Sítios de Ligação , Biocatálise , Ligação de Hidrogênio , Modelos Moleculares , Conformação Molecular , Ressonância Magnética Nuclear Biomolecular/métodos , Fragmentos de Peptídeos/química , Processos Fotoquímicos , Fotorreceptores Microbianos , Ficobilinas/química , Ficocianina/química , Fitocromo A/química , Fitocromo B/química , Proteínas Quinases/química , Transdução de Sinais , Tetrapirróis/química
15.
Nature ; 471(7338): 314-6, 2011 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-21412331
16.
Nature ; 466(7308): 825-7, 2010 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-20703295
17.
Nature ; 462(7269): 15, 2009 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-19890288
18.
Science ; 325(5939): 439-44, 2009 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-19556462

RESUMO

A central problem in quantum condensed matter physics is the critical theory governing the zero-temperature quantum phase transition between strongly renormalized Fermi liquids as found in heavy fermion intermetallics and possibly in high-critical temperature superconductors. We found that the mathematics of string theory is capable of describing such fermionic quantum critical states. Using the anti-de Sitter/conformal field theory correspondence to relate fermionic quantum critical fields to a gravitational problem, we computed the spectral functions of fermions in the field theory. By increasing the fermion density away from the relativistic quantum critical point, a state emerges with all the features of the Fermi liquid.

19.
Science ; 323(5916): 888-90, 2009 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-19213906
20.
Nature ; 457(7229): 546-7, 2009 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-19177120
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