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arXiv · 0707.3017

Diamagnetism of doped two-leg ladders and probing the nature of their commensurate phases

G. Roux·E. Orignac·S. R. White·D. Poilblanc
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Abstract

We study the magnetic orbital effect of a doped two-leg ladder in the presence of a magnetic field component perpendicular to the ladder plane. Combining both low-energy approach (bosonization) and numerical simulations (density-matrix renormalization group) on the strong coupling limit (t-J model), a rich phase diagram is established as a function of hole doping and magnetic flux. Above a critical flux, the spin gap is destroyed and a Luttinger liquid phase is stabilized. Above a second critical flux, a reentrance of the spin gap at high magnetic flux is found. Interestingly, the phase transitions are associated with a change of sign of the orbital susceptibility. Focusing on the small magnetic field regime, the spin-gapped superconducting phase is robust but immediately acquires algebraic transverse (i.e. along rungs) current correlations which are commensurate with the 4k_F density correlations. In addition, we have computed the zero-field orbital susceptibility for a large range of doping and interactions ratio J/t : we found strong anomalies at low J/t only in the vicinity of the commensurate fillings corresponding to delta = 1/4 and 1/2. Furthermore, the behavior of the orbital susceptibility reveals that the nature of these insulating phases is different: while for delta = 1/4 a 4k_F charge density wave is confirmed, the delta = 1/2 phase is shown to be a bond order wave.

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G. Roux, E. Orignac, S. R. White, D. Poilblanc. 2007-11-05. Diamagnetism of doped two-leg ladders and probing the nature of their commensurate phases. https://doi.org/10.1103/physrevb.76.195105

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