A5070594067- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Quantum many-body systems
- Nuclear materials and radiation effects
- Musicology and Musical Analysis
- Music Technology and Sound Studies
- Topological Materials and Phenomena
- Quantum chaos and dynamical systems
- Multiferroics and related materials
- Theoretical and Computational Physics
- Magnetic and transport properties of perovskites and related materials
- Numerical Methods and Algorithms
- Numerical methods in inverse problems
- Software Testing and Debugging Techniques
- Quantum Mechanics and Non-Hermitian Physics
- Algebraic structures and combinatorial models
- Seismic Imaging and Inversion Techniques
- Tensor decomposition and applications
- Model Reduction and Neural Networks
- Multimedia Communication and Technology
- Music and Audio Processing
- Nuclear Materials and Properties
- Model-Driven Software Engineering Techniques
- Inorganic Fluorides and Related Compounds
Boston University
2023-2024
Max Planck Institute for the Physics of Complex Systems
2019-2024
Max Planck Institute for Physics
2024
TU Dortmund University
2019
The Ce3+ pseudospin-1/2 degrees of freedom in the pyrochlore magnet Ce2Zr2O7 are known to possess dipole-octupole character, making it a candidate for novel quantum spin liquid ground states at low temperatures. We report new polarized neutron diffraction temperatures, as well heat capacity (Cp) measurements on single crystal Ce2Zr2O7. former bears both similarities and differences with that measured from canonical dipolar ice compound Ho2Ti2O7, while latter rises sharply initially...
A reassessment of the ground state a quantum spin liquid candidate suggests is sensitive to imperceptible change in chemical composition, an insight that could help tuning system exotic, quantum-disordered phases.
The complexity of quantum many-body problems scales exponentially with the size system, rendering any finite-size scaling analysis a formidable challenge. This is particularly true for methods based on full representation wave function, where one simply accepts enormous Hilbert space dimensions and performs linear algebra operations, e.g., finding ground state Hamiltonian. If system satisfies an underlying symmetry operator degenerate spectrum commutes Hamiltonian, it can be...
The complexity of quantum many-body problems scales exponentially with the size system, rendering any finite-size scaling analysis a formidable challenge. This is particularly true for methods based on full representation wave function, where one simply accepts enormous Hilbert space dimensions and performs linear algebra operations, e.g., finding ground state Hamiltonian. If system satisfies an underlying symmetry operator degenerate spectrum commutes Hamiltonian, it can be...
We use a combination of three computational methods to investigate the notoriously difficult frustrated three-dimensional pyrochlore $S=\frac{1}{2}$ quantum antiferromagnet, at finite temperature $T$: canonical typicality for cluster $2\ifmmode\times\else\texttimes\fi{}2\ifmmode\times\else\texttimes\fi{}2$ unit cells (i.e., 32 sites), finite-$T$ matrix product state method on larger with 48 sites, and numerical linked expansion (NLCE) using clusters up 25 lattice including nontrivial...
We address the ground-state properties of long-standing and much-studied three-dimensional quantum spin liquid candidate, $S=\frac{1}{2}$ pyrochlore Heisenberg antiferromagnet. By using SU(2) density-matrix renormalization group (DMRG), we are able to access cluster sizes up 128 spins. Our most striking finding is a robust spontaneous inversion symmetry breaking, reflected in an energy density difference between two sublattices tetrahedra, familiar as starting point earlier perturbative...
The pyrochlore magnet ${\mathrm{Ce}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ has attracted much attention as a quantum spin ice candidate whose novelty derives in part from the dipolar-octupolar nature of ${\mathrm{Ce}}^{3+}$ pseudospin-1/2 degrees freedom it possesses. We report heat capacity measurements on single crystal samples down to $T\ensuremath{\sim}0.1\phantom{\rule{4pt}{0ex}}\mathrm{K}$ magnetic field along $[1,\overline{1},0]$ direction. These show that broad hump zero-field moves...
We report new magnetic heat capacity measurements of a high quality single crystal the dipole-octupole pyrochlore Ce$_2$Hf$_2$O$_7$ down to temperature $T = 0.02$ K, factor three lower than those previously reported. These show two-peaked structure, with Schottky-like peak at $T_1 \sim 0.065$ similar what is observed in its sister Ce-pyrochlores Ce$_2$Zr$_2$O$_7$ and Ce$_2$Sn$_2$O$_7$. However second, sharper $T_2 0.025$ which signifies entrance ground state, as even most abrupt...
We propose a simple family of valence-bond crystals as potential ground states the $S=1/2$ and $S=1$ Heisenberg antiferromagnet on pyrochlore lattice. Exponentially numerous in linear size system, these can be visualized hard-hexagon coverings, with each hexagon representing resonating ring. This ensemble spontaneously breaks rotation, inversion, translation symmetries. A simple, yet accurate, variational wave function allows precise determination energy, confirmed by density matrix...
Non-Hermitian quantum systems can exhibit spectral degeneracies known as exceptional points, where two or more eigenvectors coalesce, leading to a nondiagonalizable Jordan block. It is that symmetries enhance the abundance of points in noninteracting systems. Here we investigate fate such symmetry protected presence preserving interaction between fermions and find (i) are stable interaction. Their propagation through parameter space leads formation characteristic ``fans.'' In addition, (ii)...
The ${\mathrm{Ce}}^{3+}$ pseudospin-$1/2$ degrees of freedom in ${\mathrm{Ce}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ possess both dipolar and octupolar character which enables the possibility novel quantum spin liquid ground states this material. Here we report muon relaxation rotation ($\ensuremath{\mu}\mathrm{SR}$) measurements on single-crystal samples zero magnetic field fields directed along $[1,\overline{1},0]$ $[1,1,1]$ crystallographic directions, for longitudinal transverse to...
Time crystals appear when systems display a commensurate spontaneous breaking of the discrete time translational invariance imposed by an external periodic drive. No consensus on definition has been reached as yet, but important aspects comprise robustness against small variations parameters and initial quantum state. Often, disorder interaction are thought to be essential ingredients for occurrence crystals. We study finite-length polarized XX spin chain engineered spectrum equidistant...
We report new heat capacity measurements on single crystal Ce$_2$Zr$_2$O$_7$ down to $\sim$ 0.1 K in a magnetic field along the $[1,\bar{1}, 0]$ direction. These show that broad hump zero-field moves higher temperature with increasing strength and is split into two humps by at 2 T. separate features are due decomposition of pyrochlore lattice effectively decoupled chains for fields this direction: one set ($\alpha$-chains) polarized while other ($\beta$-chains) remains free. Our theoretical...
We study the $S=\frac{1}{2}$ pyrochlore Heisenberg antiferromagnet in a magnetic field. Using large-scale density-matrix renormalization group calculations for clusters with up to 128 spins, we find indications of finite triplet gap, causing threshold field nonzero magnetization curve. obtain robust saturation consistent magnon crystal, although corresponding $5/6$ plateau is very slim and possibly unstable. Most remarkably, there pronounced apparently $1/2$ where ground state breaks...
We study classical spin ice under uniaxial strain along the $[111]$ crystallographic axis. Remarkably, such preserves extensive degeneracy and corresponding Coulomb phase. The emergent monopole excitations remain thermodynamically deconfined exactly as in isotropic case. However, their motion local heat bath dynamics depends qualitatively on sign of strain. In low-temperature limit for negative strain, monopoles diffuse, while positive they localize. Introducing additional ring exchange into...
We study classical spin ice under uniaxial strain along the [111] crystallographic axis. Remarkably, such preserves extensive degeneracy and corresponding Coulomb phase. The emergent monopole excitations remain thermodynamically deconfined exactly as in isotropic case. However, their motion local heat bath dynamics depends qualitatively on sign of strain. In low-temperature limit for negative strain, monopoles diffuse, while positive they localize. Introducing additional ring exchange into...
The Ce$^{3+}$ pseudospin-1/2 degrees of freedom in Ce$_2$Zr$_2$O$_7$ possess both dipolar and octupolar character which enables the possibility novel quantum spin liquid ground states this material. Here we report new muon relaxation rotation ($\mu$SR) measurements on single crystal samples zero magnetic field fields directed along $[1,\bar{1},0]$ $[1,1,1]$ crystallographic directions, for longitudinal transverse to direction polarization. Our zero-field results show no signs ordering or...
The author reflects on his work with music teachers and students during three weeks in Buenos Aires November 1994.
We propose a simple family of valence-bond crystals as potential ground states the $S=1/2$ and $S=1$ Heisenberg antiferromagnet on pyrochlore lattice. Exponentially numerous in linear size system, these can be visualized hard-hexagon coverings, with each hexagon representing resonating ring. This ensemble spontaneously breaks rotation, inversion translation symmetries. A simple, yet accurate, variational wavefunction allows precise determination energy, confirmed by DMRG numerical linked...