College of Science (UPD)

https://suri.up.edu.ph/handle/123456789/87

College of Science

The research outputs, creative works, faculty researcher profiles, and funded projects of the College of Science of the University of the Philippines Diliman. This community brings together scholarly and artistic contributions from its academic departments within the SURI research repository.

Academic Units

Institute of Biology
Institute of Chemistry
Institute of Environmental Science and Meteorology
Institute of Mathematics
Marine Science Institute
Materials Science and Engineering Program
National Institute of Geological Sciences
National Institute of Molecular Biology and Biotechnology
National Institute of Physics

Welcome to the College of Science SURI Community.

From a continuous to a discrete time crystal in a dissipative atom-cavity system
(arXiv, 2020)
Keßler, Hans
;
Cosme, Jayson G.
;
Georges, Christoph
;
Mathey, Ludwig
;
Hemmerich, Andreas
We propose the dynamical stabilization of a nonequilibrium order in a driven dissipative system comprised an atomic Bose-Einstein condensate inside a high finesse optical cavity, pumped with an optical standing wave operating in the regime of anomalous dispersion. When the amplitude of the pump field is modulated close to twice the characteristic limit-cycle frequency of the unmodulated system, a stable subharmonic response is found. The dynamical phase diagram shows that this subharmonic response occurs in a region expanded with respect to that where stable limit-cycle dynamics occurs for the unmodulated system. In turning on the modulation we tune the atom-cavity system from a continuous to a discrete time crystal.
Integer effects in the entanglement and spin fluctuations of a quantum Hall system with Rashba interactions
(arXiv, 2016)
Barbarona, Rona F.
;
Paraan, Francis N. C.
We report distinct nonanalytic signatures in the spin-orbit entanglement of a 2D electron gas with Rashba interactions at integer values of the filling factor and at certain level crossings. The accompanying sharp changes in the bulk spin-orbit entanglement entropy can be probed by measuring the fluctuation in the transverse spin polarization of the electron gas.
Relativistic horizon of interacting Weyl fermions in condensed matter systems
(arXiv, 2022)
Chiu, Wei-Chi
;
Chang, Guoqing
;
Macam, Gennevieve
;
Belopolski, Ilya
;
Huang, Shin-Ming
The intersections of topology, geometry and strong correlations offer many opportunities for exotic quantum phases to emerge in condensed matter systems. Weyl fermions, in particular, provide an ideal platform for exploring the dynamical instabilities of single-particle physics under interactions. Despite its fundamental role in relativistic field theory, the concept of causality and the associated spacetime light cone and event horizon has not been considered in connection with interacting Weyl fermionic excitations in quantum matter. Here, by using charge-density wave (CDW) as an example, we unveil the behavior of interacting Weyl fermions and show that a Weyl fermion in a system can open a band gap by interacting only with other Weyl fermions that lie within its energy-momentum dispersion cone. In this sense, causal connections or interactions are only possible within overlapping dispersion cones and each dispersion cone thus constitutes a solid-state analogue of the more conventional `event horizon' of high-energy physics. Our study provides a universal framework for considering interacting relativistic quasiparticles in condensed matter by separating them into energy-like and momentum-like relationships in analogy with the time-like and space-like events in high-energy physics. Finally, we consider two different candidate materials for hosting the Weyl CDW phase: (TaSe$_4$)$_2$I and Mo$_3$Al$_2$C. Our study greatly enriches the phenomenology and unveils new connections between condensed matter and high-energy physics.
Puddle formation, persistent gaps, and non-mean-field breakdown of superconductivity in overdoped (Pb,Bi)2Sr2CuO6+δ
(arXiv, 2022)
Tromp, Willem O.
;
Benschop, Tjerk
;
Ge, Jian-Feng
;
Battisti, Irene
;
Bastiaans, Koen M.
The cuprate high-temperature superconductors exhibit many unexplained electronic phases, but it was often thought that the superconductivity at sufficiently high doping is governed by conventional mean-field Bardeen-Cooper-Schrieffer (BCS) theory[1]. However, recent measurements show that the number of paired electrons (the superfluid density) vanishes when the transition temperature Tc goes to zero[2], in contradiction to expectation from BCS theory. The origin of this anomalous vanishing is unknown. Our scanning tunneling spectroscopy measurements in the overdoped regime of the (Pb,Bi)2Sr2CuO6+δ high-temperature superconductor show that it is due to the emergence of puddled superconductivity, featuring nanoscale superconducting islands in a metallic matrix[3,4]. Our measurements further reveal that this puddling is driven by gap filling, while the gap itself persists beyond the breakdown of superconductivity. The important implication is that it is not a diminishing pairing interaction that causes the breakdown of superconductivity. Unexpectedly, the measured gap-to-filling correlation also reveals that pair-breaking by disorder does not play a dominant role and that the mechanism of superconductivity in overdoped cuprate superconductors is qualitatively different from conventional mean-field theory.