Research Highlights (2009 - 2012)

NUS physicists invented light-powered nanowalkers free of chemical wastes

The group of A/P Zhisong Wang at NUS Physics, in collaboration with colleagues A/P Johan van der Maarel and Asst/P Ruchuan Liu, have made and demonstrated a bipedal nanowalker that mimics biological counterparts in design but draws energy from light. This work appears in Physical Review Letters with a news highlight.

Suzi's SEM image of her mesocrystals selected for coverpage of NanoToday!

Suzi, a Research Fellow from the Nanomaterials Research Laboratory, submitted SEM image of her mesocrystals for NanoToday coverpage competition and her work was selected! It has now officially appeared as the coverpage image of the latest issue of NanoToday.

Quantum non-locality based on finite-speed causal influences leads to superluminal signalling

The experimental violation of Bell inequalities using space-like separated measurements precludes the explanation of quantum correlations through causal influences propagating at subluminal speed.

Anomalous heat conduction and anomalous diffusion in low dimensional nanoscale systems

Heat conduction is an important energy transport process in nature. Phonon is the major energy carrier for heat in semiconductors and dielectric materials. In analogy to Ohm's law of electrical conduction, Fourier's law is the fundamental law of heat conduction in solids.

Does noise improve a bird's spin-based compass?

According to the "radical pair" model, some migratory birds exploit the quantum phenomenon of electron spin to navigate using the Earth's magnetic field. This idea has now been bolstered by a new study from physicists in Singapore, who have shown that the spin-based process and the dynamics of a proposed "compass" molecule take place over similar timescales.

Quantized Adiabatic Transport In Momentum Space

Though topological aspects of energy bands are known to play a key role in quantum transport in solid-state systems, the implications of Floquet band topology for transport in momentum space (i.e., acceleration) have not been explored so far.

Higher order oligomerization is required for H-NS family member MvaT to form gene-silencing nucleoprotein filament

MvaT from Pseudomonas aeruginosa is a member of the histone-like nucleoid structuring protein (H-NS) family of nucleoid-associated proteins widely spread among Gram-negative bacteria that functions to repress the expression of many genes.

Nucleoprotein filament formation is the structural basis for bacterial protein H-NS gene silencing

H-NS is an abundant nucleoid-associated protein in bacteria that globally silences genes, including horizontally-acquired genes related to pathogenesis.

Fluoropolymer Drops Graphene's Resistance

It was reported that Assistant Professor Özyilmaz Barbaros from the Department of Physics at the NUS Faculty of Science and researchers from Sungkyunkwan University in Suwon, South Korea worked together to develop a simple, more permanent strategy for boosting graphene's conductance.

Prof Gong's research collaboration with China researchers

1. Long-Lasting Exponential Spreading in Periodically Driven Quantum Systems
Jiao Wang, Italo Guarneri, Giulio Casati, and Jiangbin Gong Phys. Rev. Lett. 107, 234104 (2011) – Published November 30, 2011

2. Quantum Hyperdiffusion in One-Dimensional Tight-Binding Lattices
Zhenjun Zhang, Peiqing Tong, Jiangbin Gong, and Baowen Li Phys. Rev. Lett. 108, 070603 (2012) – Published February 15, 2012

3. Preferred States of Decoherence under Intermediate System-Environment Coupling
Wen-ge Wang, Lewei He, and Jiangbin Gong, Phys. Rev. Lett. 108, 070403 (2012) – Published February 17, 2012

New Theory Explains How Objective Reality Emerges from the Strange Underlying Quantum World

Quantum theory is one of the most profound discoveries of humanity. In my view, it's on a par with Cuban cigars and single malt whiskey. The theory has been hugely successful in showing us the inner workings of the universe.

Gene silencing H-NS paralogue StpA forms a rigid protein filament along DNA that blocks DNA accessibility

Bacterial nucleoid associated proteins (NAPs) are involved in genomic DNA packaging and global gene regulation in bacteria cells. One of the widely-studied NAPs in E.coli is H-NS which is involved in global gene silencing.

Graphene gives protection from intense laser pulses

21 Aug 2011. Scientists at the National University of Singapore (NUS) , DSO National Laboratories and University of Cambridge have jointly announced a new world record in broadband non-linear optical absorption behavior using single-sheet graphene dispersions in a variety of heavy-atom solvents and film matrices.

Simulation of Chemical Isomerization Reaction Dynamics on a NMR Quantum Simulator

Quantum simulation can beat current classical computers with minimally a few tens of qubits. Here we report an experimental demonstration that a small nuclear-magnetic-resonance quantum simulator is already able to simulate the dynamics of a prototype laser-driven isomerization reaction using engineered quantum control pulses.

Observation of Long Spin Relaxation Times in Bilayer Graphene at Room Temperature

We report on the first systematic study of spin transport in bilayer graphene (BLG) as a function of mobility, minimum conductivity, charge density and temperature.

Graphene used in biomedical applications can control the fate of stem cells

It is widely believed that stem cell therapies have the potential to revolutionize the treatment of human diseases. The range of potentially ground-breaking therapies based on stem cells ranges from combating Alzheimer's Disease to regenerative medicine.

The battle to find Maxwell’s perfect image

Now scientists in the UK and Singapore have published experimental evidence that shows perfect lenses don’t need negative refraction at all – and that a simpler solution lies in a 150 year-old design pioneered by James Maxwell. If true, the discovery could be a goldmine for the computer-chip industry, allowing electronic circuits to be made far more complex than those of today. However, the work is proving so controversial that the lead scientist has become embroiled in a fiery debate with other experts in the field.

Data storage: Carbon-ferroelectric memory

A fundamental component of a field-effect transistor (FET) is the gate dielectric, which determines the number of charge carriers—electrons or electron vacancies—that can be injected into the active channel of the device.

Transition dynamics and selection of the distinct S-DNA and strand unpeeling modes of double helix overstretching

The mechanism of DNA overstretching has been a mystery for 15 years. Recently a group of scientists from National University of Singapore and Northwestern University has shown that there exist two distinct pathways for the DNA overstretching transition near 65 pN: 'unpeeling' of one strand from the other, and a "B-to-S" transition from B-DNA to an elongated double-stranded 'S-DNA' form (Fu et al., Nucleic Acids Research 2011: 38, 5594-5600). More recently, the same group of authors has found answers to basic questions concerning the dynamics of these transitions, relative stability of the two competing overstretched states, the biophysical properties of S-DNA, and whether the "B-to-S" transition requires nicks and free DNA ends. In addition to solving the mystery of DNA overstretching transition, these results have provided the most complete understanding of the response of DNA to large tension.

Roll-to-roll production of 30-inch graphene films for transparent electrodes

The efforts to make transparent conducting films from graphene have been hampered by the lack of efficient methods for the synthesis, transfer and doping of graphene at the scale and quality required for applications. Here, we report the roll-to-roll production and wet-chemical doping of predominantly monolayer 30-inch graphene films grown by chemical vapour deposition onto flexible copper substrates.

Two distinct overstretched DNA states

The DNA double helix undergoes an 'overstretching' transition in a narrow force range near 65 pN. We show that overstretching in fact involves two distinct types of double-helix reorganization: slow hysteretic 'unpeeling' of one strand off the other; and a fast, non-hysteretic transition to an elongated double-stranded form.

A divalent switch drives H-NS/DNA-binding conformations between stiffening and bridging modes

Heat-stable nucleoid structuring protein (H-NS) is an abundant prokaryotic protein that plays important roles in organizing chromosomal DNA and gene silencing.

Simultaneous phase and size control of upconversion nanocrystals through lanthanide doping

Singapore scientists from NUS, the Agency for Science, Technology and Research (A*STAR), NTU and King Abdullah University of Science and Technology (KAUST) have discovered a new synthetic strategy for controlling the properties of ultra-small luminescent nanocrystals. Their findings have been published in the prestigious Nature journal on 25 February 2010.

Capillarity-Assisted Assembly of Carbon Nanotube Microstructures with Organized Initiations

In this work, detailed studies of three different capillary-assisted techniques for the formations of large-scale multiwalled carbon-nanotube (MWNT)-based microstructures were presented. These new insights and techniques presented could further encourage the use of self-organized MWNT structures with initiation as a flexible and viable route for the implementations of carbon-nanotube-based electronic devices.

Universal dynamical decoupling: Two-qubit states and beyond

Uhrig's dynamical decoupling pulse sequence has emerged as a universal and highly promising approach to decoherence suppression. So far, both the theoretical and experimental studies have examined single-qubit decoherence only. This work extends Uhrig's universal dynamical decoupling from one-qubit to two-qubit systems and even to general multilevel quantum systems.

Polymer semiconductors become sophisticated

News Release (31 Dec 2009, Singapore): NUS scientists from the departments of physics and chemistry, in collaboration with Cambridge scientists, have announced their success in creating high-quality heterostructures that make polymer organic semiconductors more functional and energy-efficient. The report was carried online by Nature Materials. Heterostructures are interfaces of two or more materials with carefully selected energy-level, bandgap or refractive-index differences that enable charge-carriers, excitons and photons to be manipulated within layers as thin as a few nanometers.

A Rotational DNA Nanomotor Driven by an Externally Controlled Electric Field

Continuous rotation of DNA around its phosphate backbone is achieved with a simple nanomotor, which is driven by an electric field oscillated between four orientations (see image). The motor consists of a DNA rotor and a partially single-stranded DNA axle held between a surface and a magnetic bead. Rotation is caused by realignment of the rotor DNA with the oscillated electric field.

The security of practical quantum key distribution

Quantum key distribution (QKD) is the first quantum information task to reach the level of mature technology, already fit for commercialization. It aims at the creation of a secret key between authorized partners connected by a quantum channel and a classical authenticated channel.

Doping graphene: Molecular tuning

An article "Tuning the Electronic Structure of Graphene by an Organic Molecule" that originally appeared in J. Phys. Chem. B which Professor Feng Yuan Ping and Dr Lu Yunhaocollaborated with researchers from Zhejiang University has been highlighted in the Sept issue of NPG Asia Materials. Professor Feng and colleagues in Singapore and China report that the adsorption of organic molecules onto graphene could allow the electronic properties of graphene to be controlled and tuned. Their first-principles calculations show that a charge-transfer complex is created with the electron–acceptor molecule tetracyanoethylene (TCNE), allowing the electronic properties of graphene to be tuned by adjusting the coverage of adsorbed molecules.

A viewpoint on: Atom interferometry tests of local Lorentz invariance in gravity and electrodynamics

An article which Asst/Prof Chung Keng Yeow collaborated with researchers from UC Berkeley, Stanford University and Bremen University has been highlighted in the July issue of Physical Review D ( ). It was also selected for a viewpoint in Physics, an online publication of APS started last year that "highlights exceptional papers from the Physical Review journals" (quoted from the website).
Measuring quantum interference of atomic matter waves may help detect experimental signatures of a fundamental theory of physics. [Viewpoint on Phys. Rev. D 80, 016002 (2009)].

An omnidirectional retroreflector based on the transmutation of dielectric singularities

Cyclists and runners may one day have perfect reflecting devices to keep them safe in night-time traffic. Scientists here, working with theortical physicists from Scotland and the Czeh Republic, have married a theory of bending light with practical engineering. The team of Prof Ong Chong Kim and his collaborator Dr Ma Yun-Gui of the Temasek Laboratories and theoreticians aboard have designed a retroreflector which have potential use from road safety to radar target tracking.Their paper was published online 28 June 2009 in materials-science journal Nature Materials and in Straits Times, 4 July 2009 titled "Bright idea for bend theory".

Magnonic Spin-offs

Magnonic crystals, a lesser known analog of photonic crystals, form the basis of magnonics. It is an emerging field which aims to control the generation and propagation of information-carrying spin waves by means analogous to the control of light in photonic crystals. The Laser Brillouin Group has designed a nanostructured magnonic crystal comprising two different magnetic materials and mapped out its dispersion relations. Its frequency bandgaps exhibit magnetic-field tunability, an important property which could find applications in magnonic devices. This work published in Appl. Phys. Lett. Vol. 94 (2009) has been highlighted in Nature Materials Vol. 8 May (2009) as an article entitled Magnonic Spin-offs.

A Step Toward Superfast Carbon Memory - Graphene could make computer hard drives denser and speedier

Graphene memory can have significant advantages over today's magnetic memory. Bits can be read 30 times faster because electrons move through graphene quickly. With graphene, bits can also shrink to 10 nanometers or even smaller thus making the memory denser. In the Technology Review published by MIT on Wednesday, April 01, 2009, the work of Dr Özyilmaz Barbarosand histeam onferroelectric RAM was publicized in the article titled "A Step Toward Superfast Carbon Memory - Graphene could make computer hard drives denser and speedier" by Prachi Patel.

Having fun with dumpling skin: material physics made alive in the kitchen

Abstract. We report a school project which equips students with both theoretical and practical knowledge in material physics. We construct dumpling skins from a mixture of flour and water. A series of experiments is then conducted to quantify the toughness, hardness, and tensile strength of the skins, and how they are affected by adding other materials into the original material to form composite materials.
Print publication: Issue 2 (March 2009) . Received 25 November 2008, in final form 11 December 2008

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