Flat metasurfaces with subwavelength meta‐atoms can be designed to manipulate the electromagnetic parameters of incident light and enable unusual light–matter interactions. Although hydrogel‐based ...metasurfaces have the potential to control optical properties dynamically in response to environmental conditions, the pattern resolution of these surfaces has been limited to microscale features or larger, limiting capabilities at the nanoscale, and precluding effective use in metamaterials. This paper reports a general approach to developing tunable plasmonic metasurfaces with hydrogel meta‐atoms at the subwavelength scale. Periodic arrays of hydrogel nanodots with continuously tunable diameters are fabricated on silver substrates, resulting in humidity‐responsive surface plasmon polaritons (SPPs) at the nanostructure–metal interfaces. The peaks of the SPPs are controlled reversibly by absorbing or releasing water within the hydrogel matrix, the matrix‐generated plasmonic color rendering in the visible spectrum. This work demonstrates that metasurfaces designed with these spatially patterned nanodots of varying sizes benefit applications in anti‐counterfeiting and generate multicolored displays with single‐nanodot resolution. Furthermore, this work shows system versatility exhibited by broadband beam‐steering on a phase modulator consisting of hydrogel supercell units in which the size variations of constituent hydrogel nanostructures engineer the wavefront of reflected light from the metasurface.
This paper reports an approach for plasmonic metasurfaces with hydrogel meta‐atoms at the subwavelength scale. Periodic arrays of hydrogel nanodots with tunable diameters are fabricated on silver substrates, resulting in humidity‐responsive surface plasmon polaritons. This work demonstrates that metasurfaces designed with spatially patterned hydrogel nanodots of varying size distributions benefit applications in anti‐counterfeiting, multicolored displays, and a phase modulator.
A
bstract
We investigate the properties of the holographic entanglement entropy of the systems in which the U(1) or the translational symmetry is broken
spontaneously
. For this purpose, we define ...the entanglement density of the strip-subsystems and examine both the first law of entanglement entropy (FLEE) and the area theorem. We classify the conditions that FLEE and/or the area theorem obey and show that such a classification may be useful for characterizing the systems. We also find universalities from both FLEE and the area theorem. In the spontaneous symmetry breaking case, FLEE is always obeyed regardless of the type of symmetry: U(1) or translation. For the translational symmetry, the area theorem is always violated when the symmetry is weakly broken, independent of the symmetry breaking patterns (explicit or spontaneous). We also argue that the log contribution of the entanglement entropy from the Goldstone mode may not appear in the strongly coupled systems.
Sodium batteries have been recognized as a promising alternative to lithium‐ion batteries. However, the liquid electrolyte used in these batteries has inherent safety problems. Polymer electrolytes ...have been considered as safer and more reliable electrolyte systems for rechargeable batteries. Herein, a thermoplastic polyurethane elastomer‐based gel polymer electrolyte with high ionic conductivity and high elasticity was reported. It had an ambient‐temperature ionic conductivity of 1.5 mS cm−1 and high stretchability, capable of withstanding 610 % strain. Coordination between Na+ ions and polymer chains increased the degree of salt dissociation in the gel polymer electrolyte compared with the liquid electrolyte. An Na/Na3V2(PO4)3 cell assembled with gel polymer electrolyte exhibited good cycling performance in terms of discharge capacity, cycling stability, and rate capability, which was owing to the effective trapping ability of organic solvents in the polymer matrix and uniform flux of sodium ions through the gel polymer electrolyte.
A gel solution: A sodium‐metal cell fabricated with a sodium‐metal anode, an Na3V2(PO4)3 cathode, and a gel polymer electrolyte based on a thermoplastic polyurethane elastomer exhibits good cycling performance in terms of discharge capacity, cycling stability, and rate capability owing to effective trapping of organic solvents in the polymer matrix and uniform sodium‐ion flux through the gel polymer electrolyte.
Silicon carbide (SiC) exhibits excellent thermal conductivity. Recently, thermal conductivity that amounts to 261.5 W/m-K has been obtained in polycrystalline SiC ceramic liquid-phase sintered (LPS) ...with Y2O3-Sc2O3 additives at 2050 °C under a nitrogen atmosphere. From the additive used to the sintering atmosphere selected, many factors affect the thermal conductivity of the SiC. In this review, important factors that are known to determine the thermal conductivity of LPS-SiC (lattice oxygen/nitrogen content, porosity, grain size, grain boundary structure, phase transformation, and additive composition) have been evaluated. While reviewing the impact of each factor on thermal conductivity, hidden correlations among different factors are also discussed. Among the factors that are claimed to be important, we suggest a few factors that are more critical to thermal conductivity than others. Based on the most critical factors on the thermal conductivity of LPS-SiC, a complete engineers’ guide for high thermal conductivity LPS-SiC is proposed.
Complexity of holographic superconductors Yang, Run-Qiu; Jeong, Hyun-Sik; Niu, Chao ...
The journal of high energy physics,
04/2019, Letnik:
2019, Številka:
4
Journal Article
Recenzirano
Odprti dostop
A
bstract
We study the complexity of holographic superconductors (Einstein-Maxwell-complex scalar actions in
d
+ 1 dimension) by the “complexity = volume” (CV) conjecture. First, it seems that there ...is a universal property: the superconducting phase always has a smaller complexity than the unstable normal phase below the critical temperature, which is similar to a free energy. We investigate the temperature dependence of the complexity. In the low temperature limit, the complexity (of formation) scales as
T
α
, where α is a function of the complex scalar mass
m
2
, the U(1) charge
q
, and dimension
d
. In particular, for
m
2
= 0, we find
α
=
d
−1, independent of
q
, which can be explained by the near horizon geometry of the low temperature holographic superconductor. Next, we develop a general numerical method to compute the
time-dependent
complexity by the CV conjecture. By this method, we compute the time-dependent complexity of holographic superconductors. In both normal and superconducting phase, the complexity increases as time goes on and the growth rate saturates to a temperature dependent constant. The higher the temperature is, the bigger the growth rate is. However, the growth rates do not violate the Lloyd’s bound in all cases and saturate the Lloyd’s bound in the high temperature limit at a late time.
Pole-skipping in rotating BTZ black holes Jeong, Hyun-Sik; Ji, Chang-Woo; Kim, Keun-Young
The journal of high energy physics,
08/2023, Letnik:
2023, Številka:
8
Journal Article
Recenzirano
Odprti dostop
A
bstract
Motivated by the connection between pole-skipping phenomena of two point functions and four point out-of-time-order correlators, we study the pole-skipping phenomena for rotating BTZ black ...holes. In particular, we investigate the effect of rotations on the pole-skipping point for various fields with spin
s
= 1
/
2
,
1
,
2
/
3, extending the previous research for
s
= 0
,
2. We derive an analytic full tower of the pole-skipping points of fermionic (
s
= 1
/
2) and vector (
s
= 1) fields by the exact holographic Green’s functions. For the
non-extremal
black hole, the leading pole-skipping frequency is
ω
leading
= 2
πiT
h
(
s
− 1 +
ν
Ω)
/
(1 − Ω
2
) where
T
h
is the temperature, Ω the rotation, and
ν
:= (∆
+
− ∆
−
)
/
2, the difference of conformal dimensions (∆
±
). These are confirmed by another independent method: the near-horizon analysis. For the
extremal
black hole, we find that the leading pole-skipping frequency can occur at
ω
leading
extremal
= −2
πiT
R
(
s
+ 1) only when
ν
=
s
+ 1, where
T
R
is the temperature of the right moving mode. It is non-trivial because it cannot be achieved by simply taking the extreme limit (
T
h
→ 0
,
Ω → 1) of the non-extremal black hole result.
This article proposes a bandgap reference (BGR) recursive low-dropout (LDO) regulator chip that achieves a high power supply rejection (PSR) in the low- to mid-frequency range. The presented LDO ...design enables the total PSR of LDO to be free from the finite ripple-rejection of the BGR circuit, resulting in low design complexity and low power consumption. To improve the PSR further, the gate buffer is modified to provide an additional ripple feedforward cancellation. The modified gate buffer also offers fast transient response and stable operation. Moreover, a light-load stabilizer loop is also suggested to provide high stability over all load conditions. A prototype chip able to supply up to 300 mA output current was implemented by 0.5- μ m 5-V CMOS devices. The PSR was measured to be -102 to -80 dB at frequencies from 100 Hz to 0.1 MHz, which is higher than that of prior LDOs with C OUT ≥ 1 μ F. The proposed LDO consumes only 50 μ A at a load current of 300 mA, and a peak current efficiency of 99.98% was achieved. The line and load regulations were measured as 0.003%/V and 0.28%/A, respectively. This chip shows a figure-of-merit of 11 ps in the transient response.
A
bstract
We employ a deep learning method to deduce the
bulk
spacetime from
boundary
optical conductivity. We apply the neural ordinary differential equation technique, tailored for continuous ...functions such as the metric, to the typical class of holographic condensed matter models featuring broken translations: linear-axion models. We successfully extract the bulk metric from the boundary holographic optical conductivity. Furthermore, as an example for real material, we use experimental optical conductivity of UPd
2
Al
3
, a representative of heavy fermion metals in strongly correlated electron systems, and construct the corresponding bulk metric. To our knowledge, our work is the first illustration of deep learning bulk spacetime from
boundary
holographic or experimental conductivity data.
A
bstract
We study the scrambling properties of (
d
+ 1)-dimensional hyperbolic black holes. Using the eikonal approximation, we calculate out-of-time-order correlators (OTOCs) for a Rindler-AdS ...geometry with AdS radius
ℓ
, which is dual to a
d
-dimensional conformal field theory (CFT) in hyperbolic space with temperature
T
= 1
/
(2
π ℓ
). We find agreement between our results for OTOCs and previously reported CFT calculations. For more generic hyperbolic black holes, we compute the butterfly velocity in two different ways, namely: from shock waves and from a pole-skipping analysis, finding perfect agreement between the two methods. The butterfly velocity
v
B
(
T
) nicely interpolates between the Rindler-AdS result
v
B
T
=
1
2
π
ℓ
=
1
d
−
1
and the planar result
v
B
T
≫
1
ℓ
=
d
2
d
−
1
.
The widespread use of thermoelectric technology is constrained by a relatively low conversion efficiency of the bulk alloys, which is evaluated in terms of a dimensionless figure of merit (zT). The ...zT of bulk alloys can be improved by reducing lattice thermal conductivity through grain boundary and point-defect scattering, which target low- and high-frequency phonons. Dense dislocation arrays formed at low-energy grain boundaries by liquid-phase compaction in Bi0.5Sb1.5Te3 (bismuth antimony telluride) effectively scatter midfrequency phonons, leading to a substantially lower lattice thermal conductivity. Full-spectrum phonon scattering with minimal charge-carrier scattering dramatically improved the zT to 1.86 ± 0.15 at 320 kelvin (K). Further, a thermoelectric cooler confirmed the performance with a maximum temperature difference of 81 K, which is much higher than current commercial Peltier cooling devices.
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