State Of Condensed Matter Research Articles

Generation of 13.9-mJ Terahertz Radiation from Lithium Niobate Materials.

Extremely strong-field terahertz (THz) radiation in free space has compelling applications in nonequilibrium condensed matter state regulation, all-optical THz electron acceleration and manipulation, THz biological effects, etc. However, these practical applications are constrained by the absence of high-intensity, high-efficiency, high-beam-quality, and stable solid-state THz light sources. Here, the generation of single-cycle 13.9-mJ extreme THz pulses from cryogenically cooled lithium niobate crystals and a 1.2% energy conversion efficiency from 800nm to THz are demonstrated experimentally using the tilted pulse-front technique driven by a home-built 30-fs, 1.2-Joule Ti:sapphire laser amplifier. The focused peak electric field strength is estimated to be 7.5MVcm-1 . A record of 1.1-mJ THz single-pulse energy at a 450 mJ pump at room temperature is produced and observed that the self-phase modulation of the optical pump can induce THz saturation behavior from the crystals in the substantially nonlinear pump regime. This study lays the foundation for the generation of sub-Joule THz radiation from lithium niobate crystals and will inspire more innovations in extreme THz science and applications.

Frequency-dependent surface wave suppression at the Dirac point of an acoustic graphene analog

Dirac points in the band structure of acoustic systems are essential features affording classical analogs of quantum condensed matter states. We show that measured dispersion curves near and at the Dirac point of an acoustic graphene analog can be suppressed by strong variations in the impedance boundary between free field and surface wave regimes under certain conditions. Increased Rayleigh scattering and diffractive excitation are shown to increase the dispersed surface wave pressure amplitude, circumventing the impedance-based wave suppression. The improved excitation and scattering conditions for observing acoustic Dirac points for two samples with two distinct operational frequency ranges are reported.

Far-field detection of two-dimensional terahertz topological photonic crystals

Originating from the investigation of condensed matter states, we have discovered a new material with phase transition no-trivial properties——topological insulators. With the progress in artificial metamaterials, the photonic crystals which can give rise to topological edge states that propagate around sharp corners immune to scattering have captured much attention. In this paper, according to the spatial and time reversal symmetry and quantum spin Hall effect theory, we presented a topological photonic crystal made of metallic cylinders at terahertz frequencies. By slightly expanding and shrinking the unit cell, the spatial reversal symmetry was broken and therefore, the band degeneracy was broken, realizing the topological band gap. Unidirectional topological edge states were proven to exist on a domain wall connecting two photonic crystals with opposite topological properties without back-scattering. Then we investigated the reflection spectra of the designed topological photonic crystals in the terahertz regime, which provided a new means to verify topological photonic crystals.

Defects Induced Criticality and Gapped Momentum States in Condensed Matter

There are two conventionally discussed dispersion relations (DR) in condensed matter: the gapless phonon-like DR and the DR with the energy or frequency gap. The third type of DR has been emerging in different areas of condensed matter physics: the gapped momentum states (GMS) when the DR with the gap in momentum, or k-space. Increasing interest for the gapped momentum states are related to important implications for dynamical and thermodynamic properties of the system (hydrodynamic turbulence, plasticity, failure). Traditionally GMS emerge in the Maxwell-Frenkel approach to liquid or solid viscoelasticity, relate the k-gap to dissipation and observe how the gaps in DR can continuously change from the energy to momentum space. Generalized hydrodynamics seeks to start with hydrodynamic equations for liquid properties and subsequently add non-hydrodynamic effects. GMS can also be obtained starting from solid-like elastic equations and generalizing them by adding hydrodynamic flow effects. Original interpretation of GMS and dispersion properties in condensed matter is developed considering the defects induced criticality (structural-scaling transition) in shocked liquid and solid. The nature of the viscosity limit is discussed analyzing the scenario of GMS in the presence of dynamics of collective modes of defects.

Mysterious long-living ultrahigh-pressure or secondary impact crisis

High-pressure glass has attracted interest in terms of both its fundamental state under extreme conditions and its possible applications as an advanced material. In this context, natural impact glasses are of considerable interest because they are formed under ultrahigh-pressure and high-temperature (UHPHT) conditions in larger volumes than laboratory fabrication can produce. Studying the UHPHT glasses of the unique giant Kara astrobleme (Russia), we found that the specific geological position of the UHPHT melt glass veins points to an origin from a secondary ultrahigh-pressure (UHP) melt according to the characteristics of the host suevites, which suggest later bottom flow. Here, we propose a fundamentally novel model involving an upward-injected UHP melt complex with complicated multi-level and multi-process differentiation based on observations of the UHP silica glass, single-crystal coesite and related UHP smectite that crystallized from an impact-generated hydrous melt. This model proposes a secondary UHP crisis during the modification stage of the Kara crater formation. The results are very important for addressing fundamental problems in fields as diverse as condensed matter states under extreme pressure and temperature (PT) conditions, material and geological reconstructions of impact structures, water conditions in mineral substances under UHP conditions in the deep Earth, and the duration and magnitude of the catastrophic effects of large asteroid impacts.

Robust Zero Energy Modes on Superconducting Bismuth Islands Deposited on Fe(Te,Se).

Topological superconductivity is one of the frontier research directions in condensed matter physics. One of the unique elementary excitations in topological superconducting state is the Majorana Fermion (mode) which is its own antiparticle and obeys the non-Abelian statistics and is thus useful for constructing the fault-tolerant quantum computation. The evidence for Majorana Fermions (mode) in condensed matter is now quickly accumulated. We deposit Bi islands on the iron-based superconductors Fe(Te,Se) and find the easily achievable zero energy modes on the tunneling spectra on some Bi islands. The zero energy mode is robust and appears everywhere on the island. Temperature and magnetic field dependence of the zero energy mode are also investigated. We attribute these zero energy modes to the Majorana modes due to the proximity effect-induced topological superconductivity on the Bi islands with strong spin-orbit coupling effect.

Strongly Compressed Few-Layered SnSe2 Films Grown on a SrTiO3 Substrate: The Coexistence of Charge Ordering and Enhanced Interfacial Superconductivity.

High pressure has been demonstrated to be a powerful approach of producing novel condensed-matter states, particularly in tuning the superconducting transition temperature (Tc) of the superconductivity in a clean fashion without involving the complexity of chemical doping. However, the challenge of high-pressure experiment hinders further in-depth research for underlying mechanisms. Here, we have successfully synthesized continuous layer-controllable SnSe2 films on SrTiO3 substrate using molecular beam epitaxy. By means of scanning tunneling microscopy/spectroscopy (STM/S) and Raman spectroscopy, we found that the strong compressive strain is intrinsically built in few-layers films, with a largest equivalent pressure up to 23 GPa in the monolayer. Upon this, unusual 2 × 2 charge ordering is induced at the occupied states in the monolayer, accompanied by prominent decrease in the density of states (DOS) near the Fermi energy (EF), resembling the gap states of CDW reported in transition metal dichalcogenide (TMD) materials. Subsequently, the coexistence of charge ordering and the interfacial superconductivity is observed in bilayer films as a result of releasing the compressive strain. In conjunction with spatially resolved spectroscopic study and first-principles calculation, we find that the enhanced interfacial superconductivity with an estimated Tc of 8.3 K is observed only in the 1 × 1 region. Such superconductivity can be ascribed to a combined effect of interfacial charge transfer and compressive strain, which leads to a considerable downshift of the conduction band minimum and an increase in the DOS at EF. Our results provide an attractive platform for further in-depth investigation of compression-induced charge ordering (monolayer) and the interplay between charge ordering and superconductivity (bilayer). Meanwhile, it has opened up a pathway to prepare strongly compressed two-dimensional materials by growing onto a SrTiO3 substrate, which is promising to induce superconductivity with a higher Tc.

Amorphous physics and materials: Interstitialcy theory of condensed matter states and its application to non-crystalline metallic materials**Project supported by the Ministry of Education and Science of the Russian Federation (Grant No. 3.114.2014/K).

A comprehensive review of a novel promising framework for the understanding of non-crystalline metallic materials, i.e., interstitialcy theory of condensed matter states (ITCM), is presented. The background of the ITCM and its basic results for equilibrium/supercooled liquids and glasses are given. It is emphasized that the ITCM provides a new consistent, clear, and testable approach, which uncovers the generic relationship between the properties of the maternal crystal, equilibrium/supercooled liquid and glass obtained by melt quenching.

Quasicrystals. A Primer, second edition. By Christian Janot. Oxford Classic Texts in the Physical Sciences. Oxford University Press, 2012. Pp. 427. Price GBP 42.50 (paperback). ISBN 978-0-19-965740-7.

This book on quasicrystals by C. Janot was first published in 1992, with a second edition in 1994. This version of the book is the same as the second edition, but has a foreword by Dan Shechtman, who received the Nobel Prize in Chemistry in 2011. The book is written for a non-specialist audience in a very pedagogical way. After a general introduction on How to fill space with atoms in condensed matter states, the second chapter presents the different ways to synthesize and characterize quasicrystals. The third chapter gives an introduction to high-dimensional (or superspace) crystallography, starting with simple one-dimensional quasicrystals, with a generalization then to three-dimensional quasicrystals. The fourth chapter, Where are the atoms?, presents a few examples of structural analysis in which the high-dimensional approach is used. The fifth chapter deals with the dynamics of quasicrystals and phonons, but also introduces the notion of phasons and the concept of dislocations in quasicrystals. The last chapter presents a discussion of the difficult questions of how the quasicystalline long-range order propagates and whether it is possible with finite-range interactions. This chapter ends with a presentation of the electronic properties of quasicrystals. Each chapter ends with a few exercises, which are very useful for testing the knowledge gained from the chapter. Although the material in the book has not been updated for 20 years, this book remains a classic introduction to quasicrystals and will be very useful for an undergraduate or a curious scientist intrigued by the quasicrystalline world.

Use of quantum quenches to probe the equilibrium current patterns of ultracold atoms in an optical lattice

Atomic bosons and fermions in an optical lattice can realize a variety of interesting condensed matter states that support equilibrium current patterns in the presence of synthetic magnetic fields or non-abelian gauge fields. As a route to probing such mass currents, we propose a nonequilibrium quantum quench of the Hamiltonian that dynamically converts the current patterns into experimentally measurable real-space density patterns. We illustrate how a specific such "unidirectional" quench of the optical lattice can be used to uncover checkerboard and stripe current orders in lattice Bose superfluids and Fermi gases, as well as chiral edge currents in an integer quantum Hall state.

Advances in proposed D-Cluster inertial confiment fusion target

Our recent research has developed a technique for imbedding ultra high density deuterium "clusters" (D cluster) in Palladium (Pd) thin film. Experiments have shown that in Pd these condensed matter state clusters approach metallic conditions, exhibiting super conducting properties. This deuterium cluster is achieved through electrochemically loading-unloading deuterium into a thin metal film, such as Palladium (Pd). During the loading process, Palladium lattice expands significantly due to invasion of deuterium into the interstitial sites. With the large enough stress, some linear lattice imperfections, called dislocations, form at / transformation interface. These dislocation defects form a strong potential trap causing deuterium to condense. In the present study, a new method employing nano-structuring of the Pd is proposed to significantly improve the site density over the target volume, suggesting that a sizable region of the compressed target deuterium can reach densities an order of magnitude higher than possible with prior target designs. This improved cluster packing fraction will enable a significant increase of the fusion reaction burn density, hence the target burn-up efficiency.

Change of physical properties from atomic and molecular states to condensed matter states

It is of great interest to study how the change of state from the monomer (atomic or molecular) state to the condensed matter state arises. For this cause we pay attention to changes of physical properties from the monomer state to the condensed matter state by examining the binding energy and the energy of formation of atomic and molecular clusters as a function of cluster size. We then show how phase transitions from the gaseous monomer states to the condensed matter states arise through the formation of intermediate cluster states leading to homogeneous or heterogeneous nucleation processes. In addition, we discuss how the onset of the Bose-Einstein condensation in high temperature superconductors may occur by showing some resemblance to the nucleation processes despite intrinsic physical differences between the two processes.

Equilibrium concentration of interstitials in aluminum just below the melting temperature

Abstract A non-contact EMAT technique of ultrasonic generation and detection was used to make high temperature measurements of the C44 deviation from perfect crystal behavior just below the melting temperature and a much smaller effect for C′, which is to be expected for interstitials in FCC crystals. The results are analyzed to give a detected interstitial concentration of 1.7±0.6×10−4 just below the melting temperature of 933 K. This corresponds to a reasonable range for the interstitial formation enthalpy and entropy, and supports a major prediction of the interstitialcy theory of condensed matter states.

The shear modulus of bulk amorphous Pd 40Ni 40P 20 and its relation to viscosity and specific heat

We have measured the shear modulus and its temperature dependence of Pd 40Ni 40P 20 using an EMAT technique. Measurements were made of the temperature dependence at constant heating rate of the infinite frequency shear modulus G. Values of the shear softening parameter γ are estimated and compared with those obtainable from frequency dependent shear moduli, specific heat and viscosity measurements. There is overall agreement with the Interstitialcy Theory of Condensed Matter States.

The Shear Modulus of Vit 1 in the Supercooled Liquid and Glassy State

AbstractUsing a non-contact electromagnetic-acoustic transformation (EMAT) technique, we have measured the temperature dependence of the infinite frequency shear modulus of Vit 1 at constant heating rate in the glassy and supercooled liquid states. Values of the shear softening fragility parameter -dln(G/Gg/d(T/Tg) are compared with those obtainable from specific heat and viscosity measurements, using the interstitialcy theory of condensed matter states. There is overall agreement found between these independently measured values.

Evidence for the self-interstitial model of liquid and amorphous states from lattice parameter measurements in krypton

One of the most unexpected and surprising predictions of a recently proposed interstitialcy model for condensed matter states is that the self-interstitial concentration just below the melting point should be only an order of magnitude below the vacancy concentration. This prediction can be tested using existing lattice parameter measurements if a suitable method of estimating the defect-free crystal expansion is found. We have developed such a test and deduce an interstitial concentration of 7 × 10 −4 near the triple point of krypton. This value is a striking confirmation of one of the boldest predictions of the interstitialcy model of condensed matter states. For copper, silver, gold and aluminum, where the defect density is smaller, less certain but positive evidence for interstitials in thermal equilibrium is also obtained.

Interstitial resonance modes as a source of the boson peak in glasses and liquids

Although it is recognized that the boson peak is a universal and fundamental feature of glass and liquid dynamics arising from low-frequency vibrational modes which are absent in crystals, the source of these modes is still under investigation. The effects are detected as a “bump” in low temperature specific heat measurements, an excess vibrational density of states in inelastic neutron scattering and the “boson” peak in Raman scattering. It is shown that the magnitude, location, and softening of the Boson peak as it persists into the supercooled liquid state are well accounted for by the interstitialcy model of condensed matter states as the resonance modes of self-interstitials.

The Shear Modulus of Liquids

According to the interstitialcy model of condensed matter states, liquids are crystals containing a few percent of self-interstitials in thermal equilibrium. Glasses are frozen liquids. The model is expressed in terms of the properties of the shear modulus, which decreases exponentially with the interstitial concentration and temperature in the liquid state, and can be nearly as large as the crystalline value in the supercooled liquid near the glass temperature. Available experimental data support the model predictions, showing that the shear modulus plays a central role in the description of thermodynamic and kinetic properties of liquids and glasses.

Self-interstitials as basic structural units of liquids and glasses

A recently given interstitialcy model for simple condensed matter states is tested by comparing predicitions of the model with available evidence for (1) the structure as given by the radial distribution function, (2) the dynamics of glasses found for the generalized vibrational density of states from inelastic neutron scattering measurements, and thermodynamic properties in the crystalline, glassy and liquid states given by (3) lattice parameter measurement determination of the thermal equilibrium concentration of interstitials in the crystalline stage, (4) the ratio of Young's modulus to volume changes during relaxation in the glassy state, and (5) the magnitude and temperature dependence of the specific heat in the liquid state. The structure, dynamics and thermodynamic properties are accounted for easily, simply and naturally in a quantitative, comprehensive and unified way by the interstitalcy model.

Interstitialcy model for condensed matter states of face-centered-cubic metals.

The special configuration and dynamics known for interstitialcies in face-centered-cubic metals are exploited to construct a model giving all the thermodynamic properties of crystalline, liquid, and amorphous states in a unified way. A large diaelastic softening of the shear modulus with defect concentration is derived. This leads to a softening of the interstitialcy formation energy, which, taken together with a large entropy contribution from the interstitialcy resonance modes, makes the model, which contains Lindemann's law, viable for quantitative calculations of thermodynamic properties.