Energy-gap opening and quenching in graphene under periodic external potentials

The CuO2 antiferromagnetic insulator is transformed by hole-doping into an exotic quantum fluid usually referred to as the pseudogap (PG) phase. Its defining characteristic is a strong suppression of the electronic density-of-states D(E) for energies |E| < Δ*, where Δ* is the PG energy. Unanticipated broken-symmetry phases have been detected by a wide variety of techniques in the PG regime, most significantly a finite-Q density-wave (DW) state and a Q = 0 nematic (NE) state. Sublattice-phase-resolved imaging of electronic structure allows the doping and energy dependence of these distinct broken-symmetry states to be visualized simultaneously. Using this approach, we show that even though their reported ordering temperatures TDW and TNE are unrelated to each other, both the DW and NE states always exhibit their maximum spectral intensity at the same energy, and using independent measurements that this is the PG energy Δ*. Moreover, no new energy-gap opening coincides with the appearance of the DW state (which should theoretically open an energy gap on the Fermi surface), while the observed PG opening coincides with the appearance of the NE state (which should theoretically be incapable of opening a Fermi-surface gap). We demonstrate how this perplexing phenomenology of thermal transitions and energy-gap opening at the breaking of two highly distinct symmetries may be understood as the natural consequence of a vestigial nematic state within the pseudogap phase of Bi2Sr2CaCu2O8.

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Energy gap opening in submonolayer lithium on graphene: Local density functional and tight-binding calculations

Physical Review B ◽

10.1103/physrevb.79.045417 ◽

2009 ◽

Vol 79 (4) ◽

Cited By ~ 53

Author(s):

M. Farjam ◽

H. Rafii-Tabar

Keyword(s):

Density Functional ◽

Energy Gap ◽

Local Density ◽

Tight Binding ◽

Gap Opening ◽

Local Density Functional

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The effects of the magnetopolaron on the energy gap opening in graphene

Journal of Physics Condensed Matter ◽

10.1088/0953-8984/24/13/135301 ◽

2012 ◽

Vol 24 (13) ◽

pp. 135301 ◽

Cited By ~ 10

Author(s):

Wei-Ping Li ◽

Zi-Wu Wang ◽

Ji-Wen Yin ◽

Yi-Fu Yu

Keyword(s):

Energy Gap ◽

Gap Opening

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Kondo physics in antiferromagnetic Weyl semimetal Mn3+xSn1−x films

Science Advances ◽

10.1126/sciadv.abc1977 ◽

2020 ◽

Vol 6 (35) ◽

pp. eabc1977

Author(s):

Durga Khadka ◽

T. R. Thapaliya ◽

Sebastian Hurtado Parra ◽

Xingyue Han ◽

Jiajia Wen ◽

...

Keyword(s):

Kondo Effect ◽

Energy Gap ◽

Strongly Correlated ◽

Strong Correlations ◽

Strong Electron ◽

Experimental Systems ◽

Weyl Semimetal ◽

Hall Effects ◽

Kondo Physics ◽

Gap Opening

Topology and strong electron correlations are crucial ingredients in emerging quantum materials, yet their intersection in experimental systems has been relatively limited to date. Strongly correlated Weyl semimetals, particularly when magnetism is incorporated, offer a unique and fertile platform to explore emergent phenomena in novel topological matter and topological spintronics. The antiferromagnetic Weyl semimetal Mn3Sn exhibits many exotic physical properties such as a large spontaneous Hall effect and has recently attracted intense interest. In this work, we report synthesis of epitaxial Mn3+xSn1−x films with greatly extended compositional range in comparison with that of bulk samples. As Sn atoms are replaced by magnetic Mn atoms, the Kondo effect, which is a celebrated example of strong correlations, emerges, develops coherence, and induces a hybridization energy gap. The magnetic doping and gap opening lead to rich extraordinary properties, as exemplified by the prominent DC Hall effects and resonance-enhanced terahertz Faraday rotation.

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Electromechanical responses of single-walled carbon nanotubes: Interplay between the strain-induced energy-gap opening and the pinning of the Fermi level

Journal of Applied Physics ◽

10.1063/1.2011781 ◽

2005 ◽

Vol 98 (4) ◽

pp. 044311 ◽

Cited By ~ 11

Author(s):

G. Y. Guo ◽

Lei Liu ◽

K. C. Chu ◽

C. S. Jayanthi ◽

S. Y. Wu

Keyword(s):

Carbon Nanotubes ◽

Fermi Level ◽

Energy Gap ◽

Single Walled Carbon Nanotubes ◽

Single Walled Carbon ◽

Electromechanical Responses ◽

Gap Opening ◽

Walled Carbon Nanotubes

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CRITICAL EXPONENTS OF THE TRANSPORT PROPERTIES AT THE B2⇔IC⇔C(R) TRANSITIONS IN Ti-Ni-Me SHAPE MEMORY ALLOYS

International Journal of Modern Physics B ◽

10.1142/s021797920000159x ◽

2000 ◽

Vol 14 (17) ◽

pp. 1729-1742 ◽

Cited By ~ 1

Author(s):

V. KOLOMYTSEV ◽

V. NEVDACHA ◽

L. BATAILLARD ◽

R. GOTTHARDT

Keyword(s):

Shape Memory Alloys ◽

Shape Memory ◽

Energy Gap ◽

Density Wave ◽

Normal Pressure ◽

Gap Formation ◽

Resistance Change ◽

Total Enthalpy ◽

Β Phase ◽

Gap Opening

Critical behaviour of the physical properties at the B2⇔IC ⇔C(R) phase transitions in TiNi-based shape memory alloys has been analyzed in the frame of the charge density wave (CDW) model. Variation of total resistance at the Peierls-type B2⇔IC ⇔C(R) transition in TiNiMe (Me=Cr, Fe, Al, Ge) alloys has been found to be a sum of the β-phase normal contribution, fluctuating CDW resistance ρ f (T) in the incommensurate state and resistance change due to the energy gap formation ρc(T) in the commensurate state. The fitting parameters such as the energy gap at saturation Δ(0) and the number of electrons involved in the process of the CDW's formation ψ(0) have been determined as a function of the alloy chemical composition and thermal treatment at moderate temperature. The critical resistive fluctuations in the incommensurate phase follow a power law dρ f /dt*~t*m with critical exponent m=-1. In the frame of the CDW model this means that the process of electron scattering from periodic distortion is strongly limited to a definite plane of the crystal and system is two-dimensional. The change of ρ c with temperature is controlled by the activation energy law corresponding to electron single excitations through the gap Δ(T), with a varying ψ(T) effective number of the electrons involved in the process. The total enthalpy measured during cooling is compared with the heat calculated for the energy gap opening at the Fermi level during the IC⇒C(R) transition in the frame of the Shottky anomaly approximation. Both values are of the same order. When hydrostatic pressure is applied to the material, a small drop in the conductivity is observed around P~2 GPa and interpreted as CDW pinning by commensurability locking at a temperature higher than the transition temperature at normal pressure.

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