Related papers: Multiple metamagnetic quantum criticality in Sr$_3…
We use quantum Monte Carlo simulations to study a disordered S=1/2 Heisenberg quantum spin model with three different nearest-neighbor interactions, J1<=J2<=J3, on the square lattice. We consider the regime in which J1 represents weak…
In the quasi-1D heavy-fermion system YbNi$_4$(P$_{1-x}$As$_x$)$_2$ the presence of a ferromagnetic (FM) quantum critical point (QCP) at $x_c$ $\approx 0.1$ with unconventional quantum critical exponents in the thermodynamic properties has…
Quantum fluctuations originating phase competition or geometrical frustration of spins lead to novel states such as a quantum critical point and a quantum spin liquid where the strong quantum fluctuations suppress any ordered states even at…
CoNb$_2$O$_6$ is a unique magnetic material. It features bulk three-dimensional magnetic order at low temperatures, but its quantum critical behavior in a magnetic field is well described by the one-dimensional transverse-field Ising…
The magnetic insulator copper pyrazine dinitrate comprises antiferromagnetic spin-1/2 chains that are well described by the exactly solvable one-dimensional Heisenberg model, providing a unique opportunity for a quantitative comparison…
The mechanism of the emergence of robust quantum criticality in the heavy-electron quasicrystal Yb15Al34Au51 is analyzed theoretically. By constructing a minimal model for the quasicrystal and its crystalline approximant, which contain…
We present specific heat measurements of 4% Rh-doped U(Ru,Rh)2Si2 at magnetic fields above the proposed metamagnetic transition field Hm~34 T, revealing striking similarities to the isotructural Ce analog CeRu2Si2, suggesting that strongly…
We report torque magnetization measurements in regions of the mixed state phase diagram (${\bf B}\sim\mu_o{\bf H}_{c2}$ and T$_c$/$10^3$) of the organic superconductor $\kappa-$(ET)$_2$Cu(NCS)$_2$ where quantum fluctuations are expected to…
We study in detail the dynamics of unstable two-level quantum systems by adopting the Bloch-vector representation. We identify a novel class of critical scenarios in which the so-called energy-level and decay-width vectors, ${\bf E}$ and…
Calcium ruthenate ($CaRuO_3$) is widely believed to be located close to a quantum critical point due to the strong non-Fermi-liquid behavior expressed in the temperature dependence of electronic transport, specific heat, optical…
When dimensionality is reduced, enhanced quantum fluctuations can destroy long-range phase coherence, driving a superconductor insulator transition, SIT, where disorder and electronic correlations give rise to novel many-body states. Here,…
We use the density matrix renormalization group (DMRG) and a hard-core boson map to investigate the quantum phase transitions present in the phase diagram of the frustrated Heisenberg ladder in a magnetic field. The quantum bicritical point…
We construct a two-dimensional lattice model of fermions coupled to Ising ferromagnetic critical fluctuations. Using extensive sign-problem-free quantum Monte Carlo simulations, we show that the model realizes a continuous itinerant quantum…
Scaling behavior in magnetization has been reported in a wide range of quantum spin liquid (QSL) candidates and is often interpreted as evidence for scale-free spin liquid physics. Here we present a comprehensive scaling analysis of…
We study dynamical scaling associated with a Kondo-breakdown quantum critical point (KB-QCP) of the periodic Anderson model, treated by two-site cellular dynamical mean-field theory (2CDMFT). In the quantum critical region, the staggered…
The behavior of the residual (impurity-dominated) resistivity is computed for a material near a two dimensional quantum critical point characterized by a divergent $q=0$ susceptibility. A singular renormalization of the amplitude for…
We present results of extensive finite-temperature Quantum Monte Carlo simulations on a SU(2) symmetric S=1/2 quantum antiferromagnet with a four-spin interaction [Sandvik, Phys. Rev. Lett. 98, 227202 (2007)]. Our simulations, which are…
Disorder is ubiquitous in any quantum many-body system and is usually considered to be an obstacle to the elucidation of the underlying physics of complex systems, but its presence can often introduce exotic phases of matter that cannot…
Unconventional quantum critical phenomena observed in Yb-based periodic crystals such as YbRh$_2$Si$_2$ and $\beta$-YbAlB$_4$ have been one of the central issues in strongly correlated electron systems. The common criticality has been…
We use inelastic neutron scattering to measure the magnetic fluctuations in a single crystal of the heavy fermion alloy CeCu_5.9Au_0.1 close to the antiferromagnetic quantum critical point. The energy and temperature-dependent spectra obey…