Fermi surface reconstruction and quantum oscillations in underdopedYBa2Cu3O7−xmodeled in a single bilayer with mirror symmetry broken by charge density waves

Abstract

Hole-doped high-temperature cuprate superconductors below optimum doping have electronlike Fermi surfaces occupying a small fraction of the Brillouin zone. There is strong evidence that this is linked to charge density wave (CDW) order, which reconstructs the large holelike Fermi surfaces predicted by band structure calculations. Recent experiments have revealed the structure of the two CDW components in the benchmark bilayer material YBa 2 Cu 3 O 7-x in high field where quantum oscillation (QO) measurements are performed. We have combined these results with a tight-binding description of the bands in a single bilayer to give a minimal model revealing the essential physics of the situation. Here we show that this approach, combined with the effects of spin-orbit interactions and the pseudogap, gives a good qualitative description of the multiple frequencies seen in the QO observations in this material. Magnetic breakdown through weak CDW splitting of the bands will lead to a field dependence of the QO spectrum and to the observed fourfold symmetry of the results in tilted fields.

Broken rotational symmetry on the Fermi surface of a high-Tc superconductor

“…This points to a Fermi surface with a square or diamond-like in-plane geometrystrikingly similar to the Fermi surface reconstruction predicted to occur via CDW. 17,[23][24][25][26][27] Two scenarios that could give rise to this type of reconstruction are shown in Fig. 3.…”

“…We suggest that this asymmetry in the ĉ-axis components of the wavevectors persists to at least 45 T, and that these CDWs are responsible for the Fermi surface reconstruction, as has been proposed theoretically. 17,[23][24][25][26][27] A second route to a diamond-like pocket with C 2 symmetry in the ĉ-axis tunneling requires a strong nematic distortion of the Fermi surface (see Fig. 3d, e).…”

Quantum oscillations in a bilayer with broken mirror symmetry: A minimal model forYBa2Cu3O6+δ

“…There have been many proposals [32][33][34][35][36][37][38][39][40][41][42][43] for the origin of the Fermi surface reconstruction in the cuprates. Given recent observations of (seemingly ubiquitous [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] ) incommensurate CDW order, a prime candidate for the Fermi surface is one where nodally located electron pockets are produced by incommensurate CDWs which are at least bi-axial, involving ordering at Q x = (Q, 0, 1/2) and Q y = (0, Q, 1/2).…”

“…Indeed, there is evidence for such broken symmetry in the low field charge order. 31,42 Once mirror symmetry is broken, a natural consequence is that the central 530T frequency reflects a semiclassical orbit where electrons are confined to a single layer of the bilayer, and if so, is naturally the most prominent in the regime of small interlayer tunneling. 72 We have demonstrated that the experimental observations can be generally accounted for in the context of a minimal model of a single bilayer.…”

“…Their observation in the high T c cuprate superconductors 1-15 combined with recent observations of charge density wave correlations [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] , have led to a compelling view of the non-superconducting "normal" state of the underdoped cuprates at high fields, H > H c , and low temperatures, T T c . In this regime, small electron-like Fermi pockets arise from reconstruction of a larger hole-like Fermi surface presumably due to translation symmetry breaking in the form of bidirectional 64 charge-density-wave (CDW) order [32][33][34][35][36][37][38][39][40][41][42][43] . However, to date, no theory of Fermi-surface reconstruction by a simple CDW can simultaneously account for the Fermi pockets and the relatively small magnitude of the measured specific heat, 44,45 which presumably reflects the persistence a pseudo-gap that removes other portions of the original (large) Fermi surface.…”