HPSynC 2016 Research Highlights

2018 |2017 | 2016

The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals.
The origin of uptrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals
Over last 60 years, efforts to enhance piezoelectricity generally resort to tuning the long-range ferroelectric phase transition. In the work published in the recent issue of Nature Communications (doi:10.1038/ncomms13807), the researchers revealed that small amount of nanoscale local inhomogeneity may dramatically improve the piezoelectric responses (50-80%) of a ferroelectric crystal.More...

Pressure-Induced Bandgap Optimization in Lead-Based Perovskites with Prolonged Carrier Lifetime and Ambient Retainability
Pressure-Induced Bandgap
For the first time, scientists have reached the Shockley-Queisser theory optimized bandgap for single-junction solar cells in lead-based perovskites. A new study led by HPSTAR scientists Dr.Gang Liu and Dr. Dave Mao, report an unprecedentedly tuned bandgap of the Shockley–Queisser limit and double-prolonged carrier lifetime in formamidinium lead triiodide (HC(NH2)2PbI3) in the latest issue of Advanced Functional Materials (DOI: 10.1002/adfm.201604208). More...

Pressure-Driven Cooperative Spin-Crossover, Large-Volume Collapse, and Semiconductor-to-Metal Transition in Manganese(II) Honeycomb Lattices
Pressure-Driven Cooperative Spin-Crossover
Spin crossover (SCO), an intriguing phenomenon that magnetic ions can switch between high-spin (HS) and low-spin (LS) states in response to light irradiation or temperature, is mostly observed as a spectacular molecular magnetism in 3d4-3d7 metal complexes. A joint team of researchers from UNLV, HPSynC and HPSTAR reported their breakthrough in pursuing "cooperative" pressure-driven SCO in J. Am. Chem. Soc. (DOI: 10.1021/jacs.6b10225). An abrupt pressure-driven SCO accompanying with large lattice collapses and semiconductor-to-metal transitions was achieved in two-dimensional honeycomb lattices, MnPS3 and MnPSe3, for the first time. The work opens a new avenue for the exploration of pressure-responsive multifunctional materials. More...

Pressure-Induced New Topological Weyl Semimetal Phase in TaAs
TaAs
A joint team co-led by HPSTAR scientist Wenge Yang studied the envolution of electronic and structural properties of Weyl semimetal TaAs using multiple methods. They found a pressure-induced new Weyl semimetallic phase with isoenergetic 12 Weyl nodes in TaAs. The study is published in the journal Physical Reviews Letters (DOI:https://doi.org/10.1103/PhysRevLett.117.146402). More...

Enhanced Structural Stability and Photo Responsiveness of CH3NH3SnI3 Perovskite via Pressure-Induced Amorphization and Recrystallization
CH3NH3Snl3
As part of a team led by Dr. Xujie Lü from Los Alamos National Laboratory, HPSTAR scientists Dr. Qingyang Hu and Dr. Wenge Yang recently conducted the first comparative study of a lead-free tin halide perovskite, CH3NH3SnI3, before and after high-pressure treatment up to 30 GPa at HPCAT. It became more stable after high-pressure treatment, with a three-fold increase in electrical conductivity and enhanced light absorption.(DOI: 10.1002/adma.201600771)More...

Giant Pressure-Driven Lattice Collapse Coupled with Intermetallic Bonding and Spin-State Transition in Manganese Chalcogenides
Giant Pressure-Driven Lattice Collapse
Recently, giant pressure-driven volume collapse (> 20%), a rarely reported phenomenon in condensed matter, was observed in MnS2 and MnS. The intriguing behavior was considered to be associated with the pressure-driven high-spin to low-spin transition of Mn(II), but lacking experimental evidences and in-depth understandings. An international team — UNLV, HPSynC and HPSTAR of scientists co-led by Dr. Wenge Yang dug into this phenomenon and found that the giant volume collapse was coupled with the spin state transition of Mn(II) and a semiconductor-to-metal transition. This work is published online in Angew. Chem Int. Ed., (2016) doi:10.1002/anie.201605410. More...

Synthesis of Sodium Polyhydrides at High Pressures
Synthesis of sodium polyhydrides at high pressure
Combining synchrotron x-ray diffraction and Raman spectroscopy, a team co-led by HPSTAR scientist, Duckyoung Kim, report the first observation of formation of sodium polyhydrides (NaH3 and NaH7) between two diamond tips. These results are applicable to the design of new energetic solids and high-temperature superconductors based on hydrogen rich materials. These findings were reported in Nature Communications (doi:10.1038/ncomms12267). More...

Simultaneous Band-gap Narrowing and Carrier-lifetime Prolongation of Organic-inorganic trihalide Perovskites
simultaneous band-gap narrowing
A team of HPSTAR scientists led by Dr. Gang Liu utilized high-pressure technique to tune the electrical and photovoltaic performance in organic-inorganic hybride perovskites. 70%-100% carrier-lifetime increasing was found in mildly compressed organic-inorganic trihalide perovskite together with bad-gap narrowing. The story is just published on the July 21th edition of PNAS. (doi: 10.1073/pnas.1609030113)
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Reversible Switching Between Pressure-induced Amorphization and Thermal-driven Recrystallization in VO2(B) Nanosheets
reversible switching between pressure-induced
By using the in situ synchrotron techniques at HPCAT and a series of self-designed experiments, an international joint team co-led by Dr. Wenge Yang from HPSTAR, realized a controllable phase switching between pressure-induced amorphization and thermal-driven recrytallization in VO2(B) nanosheets. They claimed that it was the first ever example of a structural memory effect observed in a strongly correlated material. The story is published in theJuly 18th edition of Nature Communications (doi:10.1038/ncomms12214).
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Electron–Rotor Interaction in Organic–Inorganic Lead Iodide Perovskites Discovered by Isotope Effects
Electron-Rotor
New work co-led by Dr. Gangliu from HPSTAR found carrier-rotor coupling effect in perovskite organic-inorganic hybrid lead iodide (CH3NH3PbI3) compounds from isotope effect. The discovery of the electron-rotor interaction would help to establish the theoretical foundation governing various energy transport, conversion, and storage sciences. The story is published in The Journal of Physical Chemistry Letters. (DOI: 10.1021/acs.jpclett.6b01199)
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FeO2 and FeOOH under deep lower-mantle conditions and Earth’s oxygen–hydrogen cycles
FeO2 and FeOOH
We breathe oxygen every day, but we might not know the Earth interior keeps approximately one million times oxygen more than the atmosphere. A team of HPSTAR scientists led by Ho-Kwang "Dave" Mao has discovered a new form of iron oxide - FeO2 that holds unprecedentedly large amount of oxygen, forming when the subducting plates carry the common “rust” (FeOOH) down into the deep mantle and controlling the flow of hydrogen and oxygen cycles in the Earth interior. Their findings are published in the June 9, 2016 issue of the journal Nature. (doi:10.1038/nature18018)
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Pressure-Induced Confined Metal from the Mott Insulator Sr 3 Ir 2 O 7
Sr3Ir2O7
Insulator-metal transition (IMT), where a system changes from insulator to metal with a largely enhanced electrical conductivity, represents an important topic in contemporary condensed matter physics. New study led by scientist Dr. Yang Ding from Center for High Pressure Science and Technology (HPSTAR) found that the material Sr3Ir2O7 undergoes an IMT and becomes a confined metal at high pressure, showing metallicity in the crystal ab-plane but insulating along the c-axis. Such unusual phenomenon resembles the strange metal phase in cuprate high-temperature superconductors. This novel discovery opens up a new field for synthesizing functional materials. The work is published this week in Physical Review Letters. (DOI:https://doi.org/10.1103/PhysRevLett.116.216402) More...

Pressure-induced superconductivity in a three-dimensional topological material ZrTe5
ZrTe5
By multiple complementary methods, new work co-led by scientists from HPSTAR, Dr. Wenge Yang, and Dr. Dave Mao, are trying to investigate possible crystal structural as well as electronic transitions in 3D topological material ZrTe5 under compression. Two pressure induced superconducting phases are found in ZrTe5. And in situ high-pressure synchrotron X-ray diffraction and Raman spectroscopy together with theoretical calculations indicate that the two-stage superconducting phases are correlated to two different crystal structural transitions at corresponding pressures. (doi: 10.1073/pnas.1601262113) More...