Condensed Matter Physics Department Winter Student Symposium
Zoom: https://tau-ac-il.zoom.us/j/87299063177
09:00-09:15 Gathering + opening remarks by the department chair
Session 1 Chair: Alon Ron
09:15-10:15
Yehezkel Amiel (Alexander Pelevsky & Gregory Rosenberg)
Pressure-Induced Superconductivity in AuAgTe₄: From Competing Orders to Enhanced Pairing
10:15-10:45
Tomer Hasharoni (Alon Ron)
Symmetry-breaking in SrAl4 probed through SHG & THG
10:45-11:15
Ariel Merlov (Tobias Holder)
Quantum tensors projection formalism and real space velocity vector fields
11:15-11:30 Break & fruitful discussions
11:30-12:30
Zhanyu Ma (Eran Sela)
Entropy, work, and entanglement in strongly correlated mesoscopic quantum systems
12:30-13:00
Idan Dror (Moshe Goldstein)
Ensemble Dependence of the Critical Exponent in Encoding-Decoding Circuits
13:00
Lunch
Pressure-Induced Superconductivity in AuAgTe₄: From Competing Orders to Enhanced Pairing
Yehezkel Amiel (Alexander Pelevsky & Gregory Rosenberg)
Superconductivity often competes with other electronic and structural orders. This talk examines how pressure can tip the balance in favor of superconductivity, with initial context from ferromagnet-superconductor heterostructures where we demonstrated recovery of superconductivity by pressure-tuning the magnetic state.
The primary focus is AuAgTe₄ (sylvanite), which we establish as a pressure-induced superconductor. At ambient pressure, charge disproportionation (Au³⁺/Ag¹⁺), distorted metal coordination, and Te–Te dimerization create a pseudogap that suppresses superconductivity. Under pressure, these distortions weaken gradually. Superconductivity emerges at 1.5 GPa with Tc ≈ 80 mK, rising until a first-order P2/c → P2/m transition near 5 GPa regularizes the structure and enhances Tc to 3.5 K.
Extended measurements to 37 GPa reveal that high-pressure behavior depends critically on hydrostatic conditions. Under hydrostatic loading, an ordered incommensurate phase emerges above 23 GPa, likely from charge disproportionation tendencies. Under non-hydrostatic conditions, structural disorder develops instead; yet superconductivity persists to 0.6 GPa on decompression, with Tc reaching 3.8 K. The correlation between preserved charge modulation and enhanced superconductivity suggests that charge-disproportionation fluctuations contribute to the pairing mechanism.
Symmetry-breaking in SrAl4 probed through SHG & THG
Tomer Hasharoni (Alon Ron)
SrAl4 belongs to a family of materials such as EuAl4, BaAl4, CaAl4 which are all structurally alike, but exhibit different phenomena. SrAl4 was reported to have a CdW order cooling down from ~240K and a structural monoclinic transition at the ~100K mark. Utilizing SHG & THG optical setup we attempt to probe the material and suggest different interpretation for its symmetries at room temperature and at lower ones - through the different phases.
Entropy, work, and entanglement in strongly correlated mesoscopic quantum systems
Zhanyu Ma (Eran Sela)
Quantum tensors projection formalism and real space velocity vector fields
Ariel Merlov (Tobias Holder)
The research has two parts, one part was numerically calculating quantum tensors with projection formalism and the 2nd order conductivity, and from that we try to calculate how the velocity vector of the wave packet, effected by 2nd order conductivity
Crumpling an ultra-thin sheet of elastic material such as Mylar into a three-dimensional structure results in the formation of a metamaterial with unusual mechanical properties. For example, under constant load, the volume of such a crumpled ball was found to decay logarithmically over many time scales, from seconds to weeks. Also, the crumpled sheet exhibits various dynamical features of complex systems. We suggest that the crumpled sheet is an aging Self-Organized Critical system and use both simulation and experiment to examine the underlying mechanics of the system.
Ensemble Dependence of the Critical Exponent in Encoding-Decoding Circuits
Idan Dror (Moshe Goldstein)
It is common in thermodynamics to use an ensemble in which calculation and reasoning is simplest, the specific ensemble should not affect the underlying physics. However, this is not the general case, as we show a quantum system in which a critical exponent of the phase transition is dependent on the chosen ensemble, as the studied quantity is highly sensitive to perturbations of the number of active sites. We show that quantum information based argument can seem to lead to a contradiction with exact calculations of the phase transition in an encoding-decoding circuit model, and that the source of the contradiction stems from the different choice of ensembles. We also show that one must be careful when interpreting quantum channels as simple classical randomness when used in non-linear contexts.
מארגני הסמינר: ד"ר יונתן ישראל וד"ר נעמי אופנהיימר
