The mission of XSG group is to study the structural, electronic, and magnetic properties of condensed matter systems at extreme conditions using novel synchrotron X-ray techniques, assisted with transport, optical, and theoretical approaches. Particular interest is placed on electronic and magnetic structure and phase behavior, as well as electronic excitations in electron stronglycorrelated systems (such as high-Tc superconductors, CMR, Mott-insulators, spin orbit coupled correlated iridates) at high pressure.
Project one: High-pressure effects on superconductivity in cuprates
Motivation: since it was discovered nearly 30 years ago, high pressure superconductivity (HTSC) in cuprates has been studied mainly by doping method. However, pressure could become another powerful tool to study the HTSC, since it can change the lattice parameter continuously without altering the chemistry of the system, which is incontrast to the doping method.
Goal: to understand the mechanism of HTSC through the study of the spin-fluctuation and stripe phase at high pressure, which are two crucial aspects for deciphering the mechanism of HTSC.
Project two: Study the pressured-induced novel quantum states in transition metal oxides
Motivation: the transition metal oxides (including 3d, 4d, and 5d oxides), having comparable scales for their kinetic energy, Coulomb interaction, and spin-orbit coupling (in 5d oxides), provide an excellent platform for studying new quantum states induced by pressure, such as spin liquid, topological insulator, Wely semi metal, confine metal, Mott transition,or even superconductivity.
Goal: Searching for the novel quantum states and understand the underlying mechanisms.
Project three: Pressures effects on the heavy-fermion systems
Motivation: During the past two decades, considerable attention has been focused on heavy fermion(HF) systems, but high pressure study remains unexplored. Pressure could have significant impacts on both Kondo effects and RKKY interaction, which could induce novel emergent phenomena.
Goal: we will focus on (1) Volume collapse of f electronmaterials; (2) Quantum criticality and quantum phase transition in heavy fermion systems; (3) Superconductivity.
Project four: Study the pressure effects on topological insulators
Motivation: topological Insulators, a new state of quantum matter known as received a great attention owing to the presence of gapless spin-filtered edge electronic states in their surfaces, which permits the dissipation less transport of charge and spin. This is also a brand new field for high pressure scientists, which could potentially have new discoveries.
Goal: Searching new quantum state and understanding the underlying physics.
New development: Compton Scattering; Quantum osillation.
Project five: study hdrides at high pressure
Rare-earth hydrides attract much attention recently due to (1) metal hydrides (MHx) provide a promising solution for a future hydrogen-based energy system (2) they display very rich structural and electrical transitions as a function of the H concentration (that could be tuned by pressure). However, so far high-pressure study on these materials is still very limited to very low pressure regime.
Synchrotron facilities:
APS: https://www1.aps.anl.gov/
proposal submission: https://www1.aps.anl.gov/Users-Information/About-Proposals/Apply-for-Time
Spring-8: http://www.spring8.or.jp/en/
proposal submission: https://user.spring8.or.jp/apps/mypage/
ESRF: http://www.esrf.eu/
proposal submission: http://www.esrf.eu/UsersAndScience/UserGuide/Applying
NSLS-II: https://www.bnl.gov/ps/nsls2/about-NSLS-II.php
proposal submission: https://www.bnl.gov/ps/
PETRA-III: http://petra3.desy.de/index_eng.html
proposal submission: https://door.desy.de/door/
NSRRC_TPS: http://tpsportal.nsrrc.org.tw/
NSRRC_TLS: http://portal.nsrrc.org.tw/
Other links:
X-ray booklet : http://xdb.lbl.gov/
X-ray interaction with Matters: http://henke.lbl.gov/optical_constants/
XAS: http://xafs.org/defaultsite
pressure tools: http://kantor.50webs.com/ruby.htm