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Home > Press > Quantum effects affect the best superconductor: Quantum effects explain why hydrogen sulphide is a superconductor at record-breaking temperatures Abstract: The theoretical results of a piece of international research published in Nature, whose first author is Ion Errea, a researcher at the UPV/EHU and DIPC, suggest that the quantum nature of hydrogen (in other words, the possibility of it behaving like a particle or a wave) considerably affects the structural properties of hydrogen-rich compounds (potential room-temperature superconducting substances). This is in fact the case of the superconductor hydrogen sulphide: a stinking compound that smells of rotten eggs, which when subjected to pressures a million times higher than atmospheric pressure, behaves like a superconductor at the highest temperature ever identified. This new advance in understanding the physics of high-temperature superconductivity could help to drive forward progress in the search for room-temperature superconductors, which could be used in levitating trains or next-generation supercomputers, for example. Superconductors are materials that carry electrical current with zero electrical resistance. Conventional or low-temperature ones behave that way only when the substance is cooled down to temperatures close to absolute zero (-273 °C o 0 degrees Kelvin). Last year, however, German researchers identified the high-temperature superconducting properties of hydrogen sulphide which makes it the superconductor at the highest temperature ever discovered: -70 °C or 203 K. The structure of the chemical bonds between atoms changes In classical or Newtonian physics it is possible to measure the position and momentum of a moving object to determine where it is going and how long it will take to reach its destination. These two properties are inherently linked. However, in the strange world of quantum physics, it is impossible, according to Heisenberg's uncertainty principle, for specific pairs of observable complementary physical magnitudes of a particle to be known at the same time. Hydrogen is the lightest element in the periodic table, so it is an atom that is very strongly affected by quantum behaviour. Its quantum nature affects the structural and physical properties of various hydrogen compounds. An example is high-pressure ice where quantum fluctuations of the proton lead to a change in the way the molecules are held together, due to the fact that the chemical bonds between atoms end up being symmetrical. The researchers in this study believe that a similar quantum hydrogen-bond symmetrisation occurs in the hydrogen sulphide superconductor. The researchers have formulated the calculations by considering the hydrogen atoms as quantum particles behaving like waves, and they have concluded that they form symmetrical bonds at a pressure similar to that used experimentally by the German researchers. So they have succeeded in explaining the phenomenon of superconductivity at record-breaking temperatures because in previous calculations hydrogen atoms were treated as classical particles, which made impossible to explain the experiment. All this highlights the fact that quantum physics and symmetrical hydrogen bonds lie behind high-temperature conductivity in hydrogen sulphide. The researchers are delighted that the good results obtained in this research show that quantitative predictions and computation can be used with complete confidence to speed up the discovery of high-temperature superconductors. According to the calculations made, the quantum symmetrisation of the hydrogen bonds has a great impact on the vibrational and superconducting properties of hydrogen sulphide. "In order to theoretically reproduce the observed pressure dependence of the superconducting critical temperature, the quantum symmetrisation needs to be taken into account," explained Ion Errea, the lead researcher in the study. This theoretical study shows that in hydrogen-rich compounds, the quantum motion of hydrogen can strongly affect the structural properties (even modifying the chemical bonding), as well as the electron-phonon interaction that drives the superconducting transition. In the view of the researchers, theory and computation have played a key role in the search for superconducting hydrides subjected to extreme compression. And they also pointed out that in the future an attempt will be made to increase the temperature until room-temperature superconductivity is achieved while dramatically reducing the pressures required. ### Additional information This international research was carried out with the collaboration of researchers from the UPV/EHU-University of the Basque Country and Donostia International Physics Center (DIPC), the UPMC Université Paris 06 (Sorbonne), the University of Cambridge (Cavendish Laboratory), the Jiangsu Normal University, the Carnegie Institution of Washington, Jilin University, and the University of Rome 'La Sapienza'. The lead researcher in the study was Ion Errea (Donostia-San Sebastian, 1984); he is a PhD holder in Physics and is currently a researcher at DIPC and a lecturer in the UPV/EHU's Department of Applied Physics. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


Wittkowski M.,ESO Garching | Arroyo-Torres B.,DIPC | Marcaide J.M.,University of Valencia | Abellan F.J.,University of Nice Sophia Antipolis | And 5 more authors.
Proceedings of the International Astronomical Union | Year: 2014

We present near-infrared spectro-interferometric studies of red supergiant (RSG) stars using the VLTI/AMBER instrument, which are compared to previously obtained similar observations of AGB stars. Our observations indicate spatially extended atmospheric molecular layers of water vapor and CO, similar as previously observed for Mira stars. Data of VY∼CMa indicate that the molecular layers are asymmetric, possibly clumpy. Thanks to the spectro-interferometric capabilities of the VLTI/AMBER instrument, we can isolate continuum bandpasses, estimate fundamental parameters of our sources, locate them in the HR diagram, and compare their positions to recent evolutionary tracks. For the example of VY CMa, this puts it close to evolutionary tracks of initial mass 25-32 M S™. Comparisons of our data to hydrostatic model atmospheres, 3d simulations of convection, and 1d dynamic model atmospheres based on self-excited pulsation models indicate that none of these models can presently explain the observed atmospheric extensions for RSGs. The mechanism that levitates the atmospheres of red supergiant is thus a currently unsolved problem. Copyright © International Astronomical Union 2015.


Racko D.,DIPC | Racko D.,Polymer Institute
Materials Science Forum | Year: 2011

In the present contribution the atomistic structure of the polymer melt at 300 K is simulated by means of molecular dynamics. The agreement with an experimental density is obtained with a deviation lower than 1%. The free volume is analyzed in 1,000 structures and 6.5 × 108 cubic Å of molecular space. A model for the free volume cavities is proposed. In the model the size and number of the cavities can be scaled by three parameters: probe radius, cavity depth and cavity threshold volume. The experimental values of the nano-sized cavity volumes as well as ortho-positronium lifetimes are obtained, as compared to models with cylindrical and spherical geometry. A typical value of the number density of free volume cavities at 0.001 Å-3 is obtained. The cavities have typically elongated shape with a side-to-length ratio 1:2.


News Article | April 8, 2016
Site: www.rdmag.com

The theoretical results of a piece of international research published in Nature, whose first author is Ion Errea, a researcher at the UPV/EHU and DIPC, suggest that the quantum nature of hydrogen (in other words, the possibility of it behaving like a particle or a wave) considerably affects the structural properties of hydrogen-rich compounds (potential room-temperature superconducting substances). This is in fact the case of the superconductor hydrogen sulphide: a stinking compound that smells of rotten eggs, which when subjected to pressures a million times higher than atmospheric pressure, behaves like a superconductor at the highest temperature ever identified. This new advance in understanding the physics of high-temperature superconductivity could help to drive forward progress in the search for room-temperature superconductors, which could be used in levitating trains or next-generation supercomputers, for example. Superconductors are materials that carry electrical current with zero electrical resistance. Conventional or low-temperature ones behave that way only when the substance is cooled down to temperatures close to absolute zero (-273 °C o 0 degrees Kelvin). Last year, however, German researchers identified the high-temperature superconducting properties of hydrogen sulphide which makes it the superconductor at the highest temperature ever discovered: -70 °C or 203 K. The structure of the chemical bonds between atoms changes In classical or Newtonian physics it is possible to measure the position and momentum of a moving object to determine where it is going and how long it will take to reach its destination. These two properties are inherently linked. However, in the strange world of quantum physics, it is impossible, according to Heisenberg's uncertainty principle, for specific pairs of observable complementary physical magnitudes of a particle to be known at the same time. Hydrogen is the lightest element in the periodic table, so it is an atom that is very strongly affected by quantum behaviour. Its quantum nature affects the structural and physical properties of various hydrogen compounds. An example is high-pressure ice where quantum fluctuations of the proton lead to a change in the way the molecules are held together, due to the fact that the chemical bonds between atoms end up being symmetrical. The researchers in this study believe that a similar quantum hydrogen-bond symmetrisation occurs in the hydrogen sulphide superconductor. The researchers have formulated the calculations by considering the hydrogen atoms as quantum particles behaving like waves, and they have concluded that they form symmetrical bonds at a pressure similar to that used experimentally by the German researchers. So they have succeeded in explaining the phenomenon of superconductivity at record-breaking temperatures because in previous calculations hydrogen atoms were treated as classical particles, which made impossible to explain the experiment. All this highlights the fact that quantum physics and symmetrical hydrogen bonds lie behind high-temperature conductivity in hydrogen sulphide. The researchers are delighted that the good results obtained in this research show that quantitative predictions and computation can be used with complete confidence to speed up the discovery of high-temperature superconductors. According to the calculations made, the quantum symmetrisation of the hydrogen bonds has a great impact on the vibrational and superconducting properties of hydrogen sulphide. "In order to theoretically reproduce the observed pressure dependence of the superconducting critical temperature, the quantum symmetrisation needs to be taken into account," explained Ion Errea, the lead researcher in the study. This theoretical study shows that in hydrogen-rich compounds, the quantum motion of hydrogen can strongly affect the structural properties (even modifying the chemical bonding), as well as the electron-phonon interaction that drives the superconducting transition. In the view of the researchers, theory and computation have played a key role in the search for superconducting hydrides subjected to extreme compression. And they also pointed out that in the future an attempt will be made to increase the temperature until room-temperature superconductivity is achieved while dramatically reducing the pressures required.


March N.H.,DIPC | March N.H.,University of Antwerp | March N.H.,University of Oxford | Chulkov E.V.,DIPC | And 2 more authors.
Phase Transitions | Year: 2010

After a survey of the solid-liquid transition, driven by phonon-phonon interactions, attention is next focussed on two phase transitions caused by electron-phonon interactions. These are (i) the Barden-Cooper-Schrieffer pure metal superconducting transition and (ii) the original Peierls instability. These have closely similar forms for the respective transition temperatures, both being related to energy gaps. Spin-phonon interactions are then discussed in relation to spin-Peierls materials. Finally, magnon-magnon interactions are treated in the context of the ferromagnetic-paramagnetic transition in the itinerant electron systems Fe, Co and Ni. Heuristic and phenomenological arguments, plus of course experiment, provide the basis for the conclusions drawn here. © 2010 Taylor & Francis.


March N.H.,DIPC | March N.H.,University of Antwerp | March N.H.,University of Oxford
Physics and Chemistry of Liquids | Year: 2014

In an important study, Z. D. Zhang proposed a precise set of critical exponents for the 3d Ising model. The presently intractable mathematics of this model was bypassed via two conjectures. Because this has raised some controversy, we here propose a generalisation if the exponent (Formula presented.) should prove to be different from zero. As a result, the critical exponent (Formula presented.) may be worthy of further experimental study. © 2014, © 2014 Taylor & Francis.


March N.H.,DIPC | March N.H.,University of Antwerp | March N.H.,University of Oxford | Rubio A.,Nano Bio Spectroscopy Group
Journal of Nanomaterials | Year: 2011

The delocalised nature of π-electrons in carbon-based compounds has opened a huge path for new fundamental and technological developments using carbon-based materials of different dimensionality (from clusters, to surfaces, nanotubes and graphene, among others). The success of this field has prompted the proposal that other inorganic structures based on B and N and more recently on Si and Ge could be formed with specific structural, mechanical, and electronic properties. In this paper we provide an analysis of the similarities of the two fields starting from the analysis of the Si6H6 molecule, the analogue of the benzene molecule but now being nonplanar. Then we move to the study of the two-dimensional (buckled) analogues of graphene but now formed by Si and Ge. Similarly, we look to nonplanar compounds based on boron and boron-carbon nitrogen composites. In particular, we focus on the mechanical properties of those new materials that exhibit a very high stiffness, resilience, and flexibility. Possible applications in the fields of catalysis, lubrication, electronic, and photonic devices now seem a likely by-product. We also address future directions triggered by the predicted superconducting properties of graphene, among other areas. Copyright © 2011 N. H. March and A. Rubio.


PubMed | DIPC
Type: Journal Article | Journal: Journal of physics. Condensed matter : an Institute of Physics journal | Year: 2011

Vicinal Au(111) surfaces exhibit periodic faceting within a wide range of miscut angles. There, the system segregates two alternating phases with different step lattice constants d(w) and d(n). Using a curved crystal surface that allows a smooth variation of the surface orientation, we have studied, as a function of the miscut angle, the evolution of Au(111) faceted structures by scanning tunneling microscopy, and their electronic surface states by angle-resolved photoemission. We observe that surface bands reflect the two-phase character of the faceted system, i.e. we find d(w)-and d(n)-like states that evolve accordingly to the faceted structure. Using a photoemission calculation we prove that the apparently complex topology hides relatively simple physics, i.e. the same free-electron-like dispersion and repulsive step scattering that feature surface bands in stepped noble metal surfaces. On the grounds of such simulations, we discuss the possible interference of the electronic energy in the delicate free energy balance that determines the critical size of reconstructed (d(w)) and unreconstructed (d(n)) terraces during Au faceting.

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