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The study of \emph{quantum magnetism} remains at the forefront of condensed matter physics. Spin models provide a large class of many-body systems, in which cooperative quantum phenomena can be studied in a controlled way. In addition, the \emph{neutron sc ...
The characteristic internal order of macroscopic quantum ground states in one-dimensional spin systems is usually not directly accessible, but reflected in the spin dynamics and the field dependence of the magnetic excitations. In high magnetic fields quan ...
The Falicov–Kimball model consists of itinerant lattice fermions interacting with Ising spins by an on-site potential of strength U. Kennedy and Lieb proved that at half filling there is a low temperature phase with chessboard long range order on Zd, d \ 2 ...
The temperature dependence of the structure factor S(k) of the instantaneous magnetic fluctuations in copper formate tetradeuterate has been investigated using neutron scattering techniques. Our data extend to unprecedently high temperatures (T similar to ...
We analyzed photoemission data for several doping levels of the Bi2Sr2CaCu2O8+x compounds, ranging from overdoped to underdoped. We show that the high frequency part of the spectra near (0,pi) can be described by Fermi liquid theory in the overdoped regime ...
The correlations and fluctuations in Cu(DCOO)(2). 4D(2)O, which is a good physical realization of the 2D S = 1/2 Heisenberg antiferromagnet on a square lattice, have been measured by neutron scattering measurements. The quantum fluctuations cause a non-uni ...
Structural dynamics in solid hydrogens is impulsively triggered by femtosecond excitation of the lowest Rydberg state of the NO impurity. The resulting charge redistribution induces a local radial deformation of the medium ("bubble" formation) around the ...
The spectral autocorrelation for a set of over 400 near-field photoluminescence spectra of a narrow quantum well has been evaluated. It is compared with a microscopic model of an exciton in a disorder potential. The analysis provides strong evidence for qu ...
Driven by antiferromagnetic quantum fluctuations on a deformable lattice, spin-Peierls systems dimerize magnetically and structurally at low temperatures. In this dimer phase all excitations with non-zero magnetization have a finite energy. The energy gain ...
Superconducting critical temperatures Tc are calculated as a function of the doping parameter x for generic layered Cu oxide superconductors, within the framework of a 2D-XY model with quantum phase fluctuations. The model accounts for the lower doping thr ...
