The optical conductivity of Ba(Fe$_{0.92}$Co$_{0.08}$)$_2$As$_2$ shows a clear signature of the superconducting gap, but a simple $s$-wave description fails in accounting for the low frequency response. This task is achieved by introducing an extra Drude peak in the superconducting state representing sub-gap absorption, other than thermally broken pairs. This extra peak and the coexisting $s$-wave response respect the total sum rule indicating a common origin for the carriers. We discuss the possible origins for this absorption as (i) quasiparticles due to pair-breaking from interband impurity scattering in a two band $s_{\pm}$ gap symmetry model, which includes (ii) the possible existence of impurity levels within an isotropic gap model; or (iii) an indication that one of the bands is highly anisotropic.
Non-resonant microwave absorption(NRMA) studies of superconducting MgB_2 at a frequency of 9.43 GHz in the field range -50 Gauss to 5000 Gauss are reported. The NRMA results indicate near absence of intergranular weak links. A linear temperature dependence of the lower critical field H_c1 is observed indicating a non s-wave superconductivity. However, the phase reversal of the NRMA signal which could suggest d-wave symmetry is also not observed.
Terahertz reflectance spectra of the Ca-intercalated graphite CaC6 reveal a superconducting gap below 11K. The gap signature lacks a sharp onset to full reflectivity at 2Delta, but rather shows a distribution of gap values consistent with an anisotropic gap. The experimental data were successfully fitted to the gap distribution obtained from density functional calculations by Sanna et al. (Phys.Rev. B75, 020511, 2007). The temperature dependence of the superconducting gap is characteristic for a BCS type superconductor.
Infrared absorption measurements in the range of 125 to 700 cm^(-1) have been carried out as a function of temperature upto 5 K in MgB2. The absorption spectrum is characterised by a broad band centred at 485 cm^{-1}, with shoulders at 333 and 387 cm^{-1}. Studies on the temperature dependence of absorption, indicate that these modes initially harden with the lowering of temperature, and this trend is arrested at ~ 100 K, below which they soften. Further, in the case of the mode at 333 cm^{-1}, there is a distinct softening associated with the superconducting transition at 39 K. The implicatio…
Carbon- and boron-2$p$ states of superconducting and non-superconducting boron-doped diamond samples are measured using soft X-ray emission and absorption spectroscopy. For the superconducting sample, a large density of hole states is observed in the valence band in addition to the states in the impurity band. The hole states in the valence band is located at about 1.3 eV below the valence band maximum regardless of the doping level, which cannot be interpreted within a simple rigid band model. Present experimental results, combined with the first principles calculations, suggest that supercon…
We describe a model for photon absorption by superconducting tunnel junctions in which the full energy dependence of all the quasiparticle dynamic processes is included. The model supersedes the well-known Rothwarf-Taylor approach, which becomes inadequate for a description of the small gap structures that are currently being developed for improved detector resolution and responsivity. In these junctions relaxation of excited quasiparticles is intrinsically slow so that the energy distribution remains very broad throughout the whole detection process. By solving the energy-dependent kinetic eq…
We have studied supercurrent-assisted formation of the resistive state in nano-structured Nb and NbN superconducting films after absorption of a single photon. In amorphous narrow NbN strips the probability of the resistive state formation has a pronounced spectral cut-off. The corresponding threshold photon energy decreases with the bias current. Analysis of the experimental data in the framework of the generalized hot-spot model suggests that the quantum yield for near-infrared photons increases faster than the photon nergy. Relaxation of the resistive state depends on the photon energy maki…
Correlation in temperature behavior of the optical, neutron, and muon experimental data is established for YBa2Cu3O6+x in both the pseudogap state at Tc<T<T* and the superconducting state at T<Tc. We have showed that our absorption spectra measured in the vicinity of the optical gap are very sensitive to the development of antiferromagnetic fluctuations and to the formation of a stripe structure. The inelastic neutron scattering and zero-field muon spin relaxation data analyzed in this paper were taken from the measurements made by Dai et al. and Sonier et al., respectively. Comparative analys…
We have studied the electronic structure of unoccupied states measured by O K-edge and Cu L-edge x-ray absorption spectroscopy (XAS), combined with crystal structure studied by high resolution powder x-ray diffraction (HRPXRD), of charge-compensated layered superconducting CaxLa(1-x)Ba(1.75-x)La(0.25+x)Cu3Oy (0<x<0.4, 6.4<y<7.3) cuprate. A detailed analysis shows that, apart from hole doping, chemical pressure on the electronically active CuO2 plane due to the lattice mismatch with the spacer layers greatly influences the superconducting properties of this system. The results suggest chemical …
We present the first measurements of thermal signatures of the Little-Parks effect using a highly sensitive nanocalorimeter. Small variations of the heat capacity $C\_p$ of 2.5 millions of non interacting micrometer-sized superconducting rings threaded by a magnetic flux $Φ$ have been measured by attojoule calorimetry. This non-invasive method allows the measurement of thermodynamic properties -- and hence the probing of the energy levels -- of nanosystems without perturbing them electrically. It is observed that $C\_p$ is strongly influenced by the fluxoid quantization (Little-Parks effect) n…
Taking advantage of a novel multiprobe setup we have measured, on a unique sample, the ac-magnetic susceptibility, the resistivity, the ac-specific heat and the thermopower of the superconductor heavy fermion CeCu$_{2}$Si$_{2}$ under pressure up to 5.1 GPa. At the superconducting transition temperature $T_c$, the Meissner signal corresponds to that expected for the sample volume and coincides with the specific heat jump and the resistive transition completion temperatures. Differing from previous observations, here the susceptibility measurements did not reveal any anomaly in the vicinity of t…
We measured the far infrared reflectivity of two superconducting Pr(2-x)Ce(x)CuO(4) films above and below Tc. The reflectivity in the superconducting state increases and the optical conductivity drops at low energies, in agreement with the opening of a (possibly) anisotropic superconducting gap. The maximum energy of the gap scales roughly with Tc as 2 Delta_{max} / kB Tc ~ 4.7. We determined absolute values of the penetration depth at 5 K as lambda_{ab} = (3300 +/- 700) A for x = 0.15 and lambda_{ab} = (2000 +/- 300) A for x = 0.17. A spectral weight analysis shows that the Ferrell-Glover-Tin…
The Berezinskii-Kosterlitz-Thouless (BKT) transition is expected to have a clear signature on the specific heat. The singularity at the transition temperature $T_{BKT}$ is predicted to be immeasurable, and a broad non-universal peak is expected at $T>T_{BKT}$. Up to date this has not been observed in two-dimensional superconductors. We use a unique highly sensitive technique to measure the specific heat of ultrathin Pb films. We find that thick films exhibit a specific heat jump at $T_C$ that is consistent with BCS theory. As the film thickness is reduced below the superconducting coherence le…
Local structure of NdFeAsO$_{1-x}$F$_{x}$ ($x$=0.0, 0.05, 0.15 and 0.18) high temperature iron pnictide superconductor system is studied using arsenic $K$-edge extended x-ray absorption fine structure measurements as a function of temperature. Fe-As bondlength shows only a weak temperature and F-substitution dependence, consistent with the strong covalent nature of this bond. The temperature dependence of the mean-square relative-displacements of the Fe-As bondlength are well described by the correlated-Einstein model for all the samples, but with different Einstein-temperatures for the superc…
We investigate the behavior of the Higgs (amplitude) mode when superconductivity emerges on a preexisting charge-density-wave state. We show that the weak overdamped square-root singularity of the amplitude fluctuations in a standard BCS superconductor is converted in a sharp, undamped power-law divergence in the coexisting state, reminiscent of the Higgs behavior in Lorentz-invariant theories. This effect reflects in a strong superconducting resonance in the Raman spectra, both for an electronic and a phononic mechanism leading to the Raman visibility of the Higgs. In the latter case, our res…
Recently RuB$_2$ was shown to be a possible two-gap, type-I superconductor. Temperature dependent heat capacity measurements revealed a two-gap superconducting ground state while magnetic field dependent magnetization measurements indicated surprising type-I superconductivity with a very low experimental critical field ($H_c$) $\sim$ 120 Oe. In this paper, we report direct spectroscopic evidence of two superconducting energy gaps in RuB$_2$. We have measured scanning tunnelling spectra exhibiting signature of two gaps on different grains of polycrystalline RuB$_2$, possibly originating from mu…
We present tunneling data from optimally-doped, superconducting BaFe1.86Co0.14As2 and its parent compound, BaFe2As2. In the superconductor, clear coherence-like peaks are seen across the whole field of view, and their analysis reveals nanoscale variations in the superconducting gap value, Delta. The average magnitude of 2Delta is ~7.4 kBTC, which exceeds the BCS weak coupling value for either s- or d-wave superconductivity. The characteristic length scales of the deviations from the average gap value, and of an anti-correlation discovered between the gap magnitude and the zero bias conductance…
We present femtosecond time-resolved pump-probe spectroscopic studies of a pseudogap (PG) along with the superconducting (SC) gap in an overdoped iron pnictide Ca(Fe0.927Co0.073)2As2. It is seen that the temperature evolution of the photoexcited quasiparticle (QP) relaxation dynamics, coherently excited A1g-symmetric optical phonon and two acoustic phonon dynamics behave anomalously in the vicinity of the superconducting transition temperature Tc. A continuous change in the sign of the experimentally measured transient differential reflectivity Delta_R/R signal at the zero time-delay between t…
We report on simulation results that shows optimum photon absorption by superconducting nanowires can happen at a fill-factor that is much less than 100%. We also present experimental results on high performance of our superconducting nanowire single photon detectors realized using NbTiN on oxidized silicon.
A high-Tc, superconducting Ho-Ba-Cu-O single crystal with Tc=86.8 K is investigated on a modified ESR spectrometer at temperatures T>78 K. A signal is observed, whose spectrum in the range of magnetic fields H<0.7 Oe has the form of equivalent absorption lines with an interval Δ= 0.009 Oe. Detailed measurements of the dependence of the spectrum on the amplitude of the microwave field, the temperature, and the orientation of the single crystal are reported. It is established that the absorption spectrum exhibits a typical behavior inherent in SQUIDs with a critical current that decays linearly …
The effects of absence of inversion symmetry on superconducting states are investigated theoretically. In particular we focus on the noncentrosymmetric compounds which have the cubic symmetry $O$ like Li$_2$Pt$_3$B. An appropriate and isotropic spin-orbital interaction is added in the Hamiltonian and it acts like a magnetic monopole in the momentum space. The consequent pairing wavefunction has an additional triplet component in the pseudospin space, and a Zeeman magnetic field $\bf{B}$ can induce a collinear supercurrent $\bf{J}$ with a coefficient $κ(T)$. The effects of anisotropy embedded i…
Ni-Ga bilayers are a versatile platform for exploring the competition between strongly antagonistic ferromagnetic and superconducting phases. We characterize the impact of this competition on the transport properties of highly-ballistic Al/Al2O3(/EuS)/Ni-Ga tunnel junctions from both experimental and theoretical points of view. While the conductance spectra of junctions comprising Ni (3 nm)-Ga (60 nm) bilayers can be well understood within the framework of earlier results, which associate the emerging main conductance maxima with the junction films' superconducting gaps, thinner Ni (1.6 nm)-Ga…
Under certain conditions, a fermion in a superconductor can separate in space into two parts known as Majorana zero modes, which are immune to decoherence from local noise sources and are attractive building blocks for quantum computers. Promising experimental progress has been made to demonstrate Majorana zero modes in materials with strong spin-orbit coupling proximity coupled to superconductors. Here we report signatures of Majorana zero modes in a new material platform utilizing the surface states of gold. Using scanning tunneling microscope to probe EuS islands grown on top of gold nanowi…
One of the defining features of spontaneously broken time-reversal symmetry (BTRS) is the existence of domain walls, the detection of which would be strong evidence for such systems. There is keen interest in BTRS currently, in part, due to recent muon spin rotation experiments, which have pointed towards $\textrm{Ba}_{1-x}\textrm{K}_x\textrm{Fe}_2\textrm{As}_2$ exhibiting a remarkable case of $s$-wave superconductivity with spontaneously broken time-reversal symmetry. A key question, however, is how to differentiate between the different theoretical models which describe such a state. Two par…
Y. M. Dai et al. in their recent work arXiv:1106.4430 presented a reflectivity study of the in-plance optical conductivity of a $\textrm{Ba}_{0.6}\textrm{K}_{0.4}\textrm{Fe}_2\textrm{As}_2$ (BKFA) superconductor with $T_{\textrm{c}}\approx39K$. The single crystals used in this study are of high quality and the measurements are rather accurate. The authors analyzed the optical conductivity of BKFA in the framework of the Mattis-Bardeen theory and the BCS theory of superconductivity. This analysis, however, generates a series of severe contradictions with a large body of experimental data obtain…
We study how turns and constrictions affect the resistive response of the superconducting wire after instant in time and local in space heating, which models the absorption of the single photon by the wire. We find that the presence of constriction favors detection of photons of various energies but the presence of turn increases only ability to detect relatively "low" energy photons. The main reason is that in case of constriction the current density is increased over whole length and width of the constriction while in case of the turn the current density is enhanced only near the inner corne…
Femtosecond pump-probe spectroscopy is applied to identify transient optical signatures of phase transitions in optimally doped YBa2Cu3O7-δ films. To elucidate the dynamics of superconducting and pseudogap phases, the slow thermal component is removed from the time-domain traces of photo-induced reflectivity in a high-flux regime with low frequency pulse rate. The rescaled data exhibit distinct signatures of the phase separation with abrupt changes at the onsets of TSC and TPG in excellent agreement with transport data. Compared to the superconducting phase, the response of the pseudogap phase…
We have studied the magnetic field or disorder induced insulating and metallic phases in amorphous Ta superconducting thin films. The evolution of the nonlinear transport in the insulating phase exhibits a non-monotonic behavior as the magnetic field is increased. We suggest that this observation could be an evidence of the presence of localized Cooper pairs in the insulating phase. As the metallic phase intervenes the superconducting and insulating states in Ta films, this result further reveals that Cooper pairs also exist in the metallic ground state.
Motivated by the recent experiments indicating superconductivity in metal-decorated graphene sheets, we investigate their quasi-particle structure within the framework of an effective tight-binding Hamiltonian augmented by appropriate BCS-like pairing terms for p-type order parameter. The normal state band structure of graphene is modified not only through interaction with adsorbed metal atoms, but also due to the folding of bands at Brillouin zone boundaries resulting from a $\sqrt{3}\times\sqrt{3}R30^{\circ}$ reconstruction. Several different types of pairing symmetries are analyzed utilizin…
We calculate the ultrasonic absorption and the thermal conductivity in the superconducting state of UPt$_{3}$ as functions of temperature and direction of propagation and polarization. Two leading candidates for the superconducting order parameter are considered: the $E_{1g}$ and $E_{2u}$ representations. Both can fit the data except for the ultrasonic absorption in the $A$ phase. To do that, it is necessary to suppose that the system has only a single domain, and that must be chosen as the most favorable one. However, the $E_{2u}$ theory requires fine-tuning of parameters to fit the low tempe…
Understanding the detailed behaviour of superconducting pair breaking photon detectors such as Kinetic Inductance Detectors requires knowledge of the nonequilibrium quasiparticle energy distributions. We have previously calculated the steady state distributions resulting from uniform absorption of monochromatic sub gap and above gap frequency radiation by thin films. In this work, we use the same methods to calculate the effect of illumination by broadband sources, such as thermal radiation from astrophysical phenomena or from the readout system. Absorption of photons at multiple above gap fre…
In a superconductor absorption of photons with an energy below the superconducting gap leads to redistribution of quasiparticles over energy and thus induces a strong non-equilibrium quasiparticle energy distribution. We have measured the electrodynamic response, quality factor and resonant frequency, of a superconducting aluminium microwave resonator as a function of microwave power and temperature. Below 200 mK, both the quality factor and resonant frequency decrease with increasing microwave power, consistent with the creation of excess quasiparticles due to microwave absorption. Counterint…
We investigated several FeSe single crystals grown by two different methods by utilizing experimental techniques namely, resistivity, magnetoresistance, specific heat, scanning tunneling microscopy, and spectroscopy. The residual resistivity ratio (RRR) shows systematic differences between samples grown by chemical vapor transport and flux vapor transport, indicating variance in the amount of scattering centers. Although the superconducting transition temperature $T_c$ is not directly related to RRR, our study evidences subtle differences in the features of an incipient ordering mode related t…
Signature of chiral superconducting order parameter evidenced in mesoscopic superconductors
Quantum Science Center of Guangdong-HongKong-Macau Greater Bay Area（粤港澳大湾区量子科学中心）；University of Science and Technology of China（中国科学技术大学）；The Chinese University of Hong Kong（香港中文大学）
Multiband superconductivity with dominant two-gap features are recently proposed to challenge the earlier accepted nodal $d$-wave pairing in the first unconventional superconductor CeCu$_{2}$Si$_{2}$. Here we obtain multiband Fermi-surface topology of CeCu$_{2}$Si$_{2}$ via first-principles calculations, and study the problem within an effective two hybridization band model including detailed band-structure. Within T-matrix approximation, our calculations reveal that different pairing candidates could yield qualitatively distinct features characterised by impurity-induced bound states. Except …
The local lattice structure in newly discovered LaFeAsO1-xFx superconductors is studied by extended x-ray absorption fine structure measurements. An anomalous upturn of the mean-square relative displacement of the Fe-As bond is detected below ~70 K as electron carriers are introduced,reflecting the occurrence of Fe-As bond local lattice fluctuation. Similar to that in cuprates, this lattice fluctuation exhibits an abrupt depression at the onset superconducting transition temperature. The results indicate that strong electron-lattice interaction is involved in the superconducting transition in …
We report clear observations of the magnetic Meissner effect in arrays of superconducting 4 Å carbon nanotubes grown in the linear channels of AlPO4-5 (AFI) zeolite single crystals. Both bulk magnetization and magnetic torque experiments show a clear signature of the lower critical Hc1 transition, a pronounced difference in zero-field cooled and field cooled branches during temperature sweeps below 6K, and signatures of 1D superconducting fluctuations below ~15-18 K. These experiments extend the magnetic phase diagram we obtained previously by resistive experiments [Z. Wang et al., Phys. Rev. …
We establish the quasi-one-dimensional Li purple bronze as a photoemission paradigm of Luttinger liquid behavior. We also show that generalized signatures of electron fractionalization are present in the angle resolved photoemission spectra for quasi-two-dimensional purple bronzes and certain cuprates. An important component of our analysis for the quasi-two-dimensional systems is the proposal of a ``melted holon'' scenario for the k-independent background that accompanies but does not interact with the peaks that disperse to define the Fermi surface.
Cavity spintronics recently heralded non-local magnonic signal transfer between magnetic samples. Here we show that by including superconductors in the cavity, we can make use of these principles to bring composite superconductor--ferromagnet systems to the macroscale. We analyze how a superconductor's a.c. conductivity influences the spin dynamics of a spatially separated magnet, and we discuss the potential impact on spintronic applications.
Scanning tunneling spectroscopy applied to the high-$T_{c}$ cuprates has revealed significant spatial inhomogeneity on the nanoscale. Regions on the order of a coherence length in size show variations of the magnitude of the superconducting gap of order $\pm20%$ or more. An important unresolved question is whether or not these variations are also present in the bulk, and how they influence superconducting properties. As many theories and data analyses for high-$T_{c}$ superconductivity assume spatial homogeneity of the gap magnitude, this is a pressing question. We consider the far-infrared op…
Experimental evidence for the existence of a fluctuating charge-density wave order in the pseudogap regime of YBa$_2$Cu$_3$O$_{6+x}$ has renewed interest in its interplay with superconductivity. Here, we consider the problem within a nonlinear sigma model, which was recently proposed to describe the apparent competition between the two order parameters. In particular, we use a saddle-point approximation to calculate the properties of superconducting vortex excitations within such a model. In addition, we analytically calculate a collection of experimentally observable quantities, which probe b…
More than a quarter century after the discovery of the high temperature superconductor (HTS) YBa$_2$Cu$_3$O$_{6+δ}$ (YBCO) studies continue to uncover complexity in its phase diagram. In addition to HTS and the pseudogap there is growing evidence for multiple phases with boundaries which are functions of temperature ($T$), doping (p) and magnetic field. Here we report the low temperature electronic specific heat (C$_{elec}$) of YBCO6.47 (p=0.08) up to a magnetic field (H) of 34.5 teslas (T), a poorly understood region of the underdoped H-$T$-p phase space. We observe two regimes: below a chara…
Oval-shaped resonance distortion as a signature of quasiparticle heating effect in a niobium superconducting resonator
School of Integrated Circuits, Tsinghua University（清华大学集成电路学院）；Cavendish Laboratory, University of Cambridge（剑桥大学卡文迪许实验室）；Department of Astronomy, Tsinghua University（清华大学天文系）
In order to realize superconductivity in cuprates with the T'-type structure, not only chemical substitution (Ce doping) but also post-growth reduction annealing is necessary. In the case of thin films, however, well-designed reduction annealing alone without Ce doping can induce superconductivity in the T'-type cuprates. In order to unveil the origin of superconductivity in the Ce-undoped T'-type cuprates, we have performed bulk-sensitive hard x-ray photoemission and soft x-ray absorption spectroscopies on superconducting and non-superconducting Nd$_{2-x}$Ce$_x$CuO$_4$ ($x=$ 0, 0.15, and 0.19…
Simultaneous transport and tunneling spectroscopy of moiré graphene: Distinct observation of the superconducting gap and signatures of nodal superconductivity
We report the phase diagram of $λ$-(BETS)$_2$GaCl$_4$ from rf penetration depth measurements with a tunnel diode oscillator in a pulsed magnetic field. We examined four samples with 1100 field sweeps in a range of angles with the magnetic field parallel and perpendicular to the conducting planes. In the parallel direction, $H_{c2}$ appears to include a tricritical point at 1.6 K and 10 T with a phase line that increases to 11 T as the temperature is decreased to} 500 mK. The second phase line forms a clearly defined high field low temperature region satisfying several of the conditions of the …
We present a combined experimental and theoretical analysis of the low bias conductance properties of carbon nanotubes coupled to superconducting leads. In the Kondo regime the conductance exhibits a zero bias peak which can be several times larger than the unitary limit in the normal case. This zero bias peak can be understood by analyzing the dynamics of the subgap Andreev states under an applied bias voltage. It is shown that the existence of a linear regime is linked to the presence of a finite relaxation rate within the system. The theory provides a good fitting of the experimental result…
We show that a common feature of temperature-dependent microwave absorption is the presence of absorption peaks. $ac$ loss peaks can arise when the internal $T$-dependent magnetic relaxation time crosses the measurement frequency. These features are observed in the \QTR{em}{insulating} ($Sr_{x}Ca_{14-x}Cu_{24}O_{41}$, $La_{5/3}Sr_{1/3}NiO_{4}$ and $YBa_{2}Cu_{3}O_{6.0}$), \QTR{em}{pseudo-gap} ($T>T_{c}$ in underdoped $YBa_{2}Cu_{3}O_{7-δ}$, $Hg:1223$ and $Hg:1201$) and \QTR{em}{superconducting} ($T<T_{c}$) states of the oxides. The commonality of these features suggests a magnetic (spin) mecha…
A possible superconducting gap signature with filling temperature around 40 K in hexagonal iron telluride islands
Peking University（北京大学）；ShanghaiTech University（上海科技大学）；Quantum Science Center of Guangdong–Hong Kong–Macao Greater Bay Area (Guangdong)（粤港澳大湾区量子科学中心（广东））；Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Collaborative Innovation Center of Quantum Matter（量子物质协同创新中心）；Hefei National Laboratory（合肥国家实验室）
High resolution longitudinal sound velocity measurements in a magnetic field performed in the temperature tending to zero limit reveal two distinct signatures attributable to multiple superconducting phases in URu2Si2. A step change in the sound velocity, for propagation in the basal plane, is observed at the critical field, Bc2. This step broadens considerably as T tends to Tc with a concomitant decrease in magnitude. A second step is observed at a field ~0.5 Bc2 and it's magnitude remains constant at all temperatures. Inductive measurements of the transitions in a magnetic field, however, ex…
The discovery of superconductivity at 203K in SH$_3$ is an important step toward higher values of $T_c$. Predictions based on state-of-the-art DFT for the electronic structure, including one preceding experimental confirmation, showed the mechanism to be the electron-phonon interaction. This was confirmed in optical spectroscopy measurements. For photon energies between $\sim 450$ and 600 meV in SH$_3$, the reflectance in the superconducting state is below that in its normal state. This difference decreases as $T$ approaches $T_c$. Decreasing absorption with increasing $T$ is opposite to what …
Signatures of superconducting Higgs mode in irradiated Josephson junctions
University of Würzburg（维尔茨堡大学）；Universidad Autónoma de Madrid（马德里自治大学）；Condensed Matter Physics Center (IFIMAC)（凝聚态物理中心 (IFIMAC)）；Würzburg-Dresden Cluster of Excellence ct.qmat（维尔茨堡-德累斯顿卓越集群 ct.qmat）
We show that superconductors with broken time-reversal symmetry have very specific magnetic and electric responses to inhomogeneous heating. A local heating of such superconductors induces a magnetic field with a profile that is sensitive to the presence of domain walls and crystalline anisotropy of superconducting states. A nonstationary heating process produces an electric field and a charge imbalance in different bands. These effects can be measured and used to distinguish $s+is$ and $s+id$ superconducting states in the candidate materials such as Ba$_{1-x}$K$_x$Fe$_2$As$_2$.
