[Clinical characteristics of 13 neuroendocrine prostate cancer patients]

Objective: To explore the radiological, pathological features and clinical characteristics of neuroendocrine prostate cancer patients(NEPC). Methods: The clinical characteristics and pathology data of 13 neuroendocrine prostate cancer patients treated in the Affiliated Hospital of Tianjin Medical University from January 2004 to January 2015 were analyzed retrospectively. Results: Of all 13 patients, three cases were primally diagnosed small cell cancer, and 10 cases were translated to neuroendocrine type from adenocarcinoma after endocrine therapy. Frequent urination, urgency, nocturia, and dysuria were main symptoms. Serum prostate-specific antigen (PSA) was (14.5±3.2)μg/L; the volume of prostate was enlarged, mean volume, range 28-176(45±4)ml. The lesion was moderately low signal intensity in T(2)WI, while slightly higher signal in DWI. Signal characteristic of dynamic enhanced MRI was "fast in fast out" . The expression of Synaptophysin, Chromogranin A , CD56 and Ki-67 in NEPC were highly expressed by immunohistochemistry analysis. Among them, five patients accepted intravenous chemotherapy, two cases received external radiation therapy, three cases received cryoablation and three cases received palliative therapy. Median survival time in all 13 patients was 10 months, while median survival time in patients treated by chemotherapy was 16 months . Conclusion: NEPC is a highly aggressive subtype of prostate cancer characterized by rapid disease progression, lack of treatment and worse prognosis. Therefore, patients with NEPC may benefit from early diagnosis and comprehensive treatment with chemotherapy.

[Expert consensus on the diagnosis and treatment of cryptococcal meningitis]

Cryptococcal meningitis is a common and refractory central nervous system infection, with high rates of mortality and disability. The experts of the Society of Infectious Diseases of Chinese Medical Association have reached this consensus after a thorough discussion. Based on the current situation of cryptococcal meningitis in China, the management of cryptococcal meningitis includes 6 aspects: introduction, microorganism identification, clinical manifestations and diagnosis, principles of antifungal therapy, treatment of refractory and recurrent meningitis, treatment of intracranial hypertension. There is not a separate consensus on human immunodeficiency virus (HIV) infection in patients with cryptococcal meningitis. This article focuses on different antifungal regimens and reducing intracranial pressure by reference to Infectious Disease Society of America (IDSA) guidelines. The importance of early diagnosis, combined long-term antifungal therapy, control of intracranial hypertension are emphasized.

[Clinical and genetic characteristics of congenital myasthenia syndrome with episodic apnea caused by CHAT gene mutation: a report of 2 cases]

Objective: To investigate the clinical and genetic features of congenital myasthenia syndrome with episodic apnea (CMS-EA) caused by gene mutation of choline acetyltransferase (CHAT) Methods: The clinical data of 2 patients with congenital myasthenia syndrome were collected, and both were diagnosed from 2013 to 2015 in Beijing Children's Hospital, Capital Medical University. The clinical features and gene mutation characteristics were analyzed, and the patients were followed-up for therapeutic efficacy. Results: The two patients (case 1 and case 2) had the onset soon after birth and at 3 months after birth respectively. The two patients were admitted to the PICU due to dyspnea, cyanotic episodes that required intubation. The patients had repeated apnea and became ventilator dependent. Case 1 died due to refusal of any treatment. Case 2 had a tracheotomy, and gradually weaned from ventilator after using pyridostigmine. The hospitalization of case 2 lasted 162 days. Case 2 was followed up to the age of 3 years and 4 months, and was extubated and was maintained on oral neostigmine but still had fluctuating ptosis and minor physical and mental retardation. Both cases were negative for anti-AChR, anti-acetylcholinesterase, anti-MuSK antibodies. Neostigmine test was negative in case 1 and suspiciously positive in case 2. Low-frequency repetitive nerve stimulation testing of case 2 was negative. Cranial MRI scans of both cases showed brain atrophy-like change. Genetic testing showed compound heterozygous deletions (exon 4, 5, 6) and pathogenic variant c.914T>C (p.I305T) in CHAT in case 1, compound heterozygous variants c.1007T>C (p.I336T) and c.64C>T (p.Q22X) in CHAT in case 2. To our knowledge, compound heterozygous deletions (exon 4, 5, 6) and p.Q22X were novel, previously unreported variants. Conclusion: CMS-EA usually presents at birth or in the neonatal period with hypotonia, ptosis, dysphagia due to severe bulbar weakness, and respiratory insufficiency with cyanosis and apnea. Early treatment with pyridostigmine is helpful to the improvement of clinical symptoms and prognosis.

Superconducting ECR ion source: From 24-28 GHz SECRAL to 45 GHz fourth generation ECR

The development of superconducting ECR source with higher magnetic fields and higher microwave frequency is the most straight forward path to achieve higher beam intensity and higher charge state performance. SECRAL, a superconducting third generation ECR ion source, is designed for 24-28 GHz microwave frequency operation with an innovative magnet configuration of sextupole coils located outside the three solenoids. SECRAL at 24 GHz has already produced a number of record beam intensities, such as ⁴⁰Ar¹²⁺ 1.4 emA, ¹²⁹Xe²⁶⁺ 1.1 emA, ¹²⁹Xe³⁰⁺ 0.36 emA, and ²⁰⁹Bi³¹⁺ 0.68 emA. SECRAL-II, an upgraded version of SECRAL, was built successfully in less than 3 years and has recently been commissioned at full power of a 28 GHz gyrotron and three-frequency heating (28 + 45 + 18 GHz). New record beam intensities for highly charged ion production have been achieved, such as 620 eμA ⁴⁰Ar¹⁶⁺, 15 eμA ⁴⁰Ar¹⁸⁺, 146 eμA ⁸⁶Kr²⁸⁺, 0.5 eμA ⁸⁶Kr³³⁺, 53 eμA ¹²⁹Xe³⁸⁺, and 17 eμA ¹²⁹Xe⁴²⁺. Recent beam test results at SECRAL and SECRAL II have demonstrated that the production of more intense highly charged heavy ion beams needs higher microwave power and higher frequency, as the scaling law predicted. A 45 GHz superconducting ECR ion source FECR (a first fourth generation ECR ion source) is being built at IMP. FECR will be the world's first Nb₃Sn superconducting-magnet-based ECR ion source with 6.5 T axial mirror field, 3.5 T sextupole field on the plasma chamber inner wall, and 20 kW at a 45 GHz microwave coupling system. This paper will focus on SECRAL performance studies at 24-28 GHz and technical design of 45 GHz FECR, which demonstrates a technical path for highly charged ion beam production from 24 to 28 GHz SECRAL to 45 GHz FECR.

[A preliminary research on the exosome influenced by virus infection in the renal transplantation recipients]

Objective: Virus infection is a common complication of transplantation.With the research and application of exosome is becoming more popular, this study focused on whether the virus particles and nucleic acids exist in the exosomes extracted from the plasma of recipients with virus infection after renal transplantation. Methods: A total of 10 independent transplantation recipients at Institute of Organ Transplantation, 309th Hospital of Chinese People's Liberation Army from January 2015 to July 2017 were studied in this study.5 cases of positive or suspected positive in granulocytes HCMV pp65 antigen detection and positive in plasma HCMV DNA test, and the other 5 cases of positive results in plasma BK DNA test were adopted.Exosomes were extracted from the collected plasma samples with SBI kit.Electron microscopy and nanoparticles tracing analyzer (NTA) were used for exosome analysis.Quantitative real-time PCR method was used to inspect and compare virus DNA copies number in plasma, exosome and effluent. Results: Typical exosome-like vesicle structure was observed.NTA put forward the sample concentration data from 1.2 to 4.5×10(12) particles/ml, and the particle diameters were 30-200 nm.In the qRT-PCR assays, the viral DNA quantitative results of exosome samples are lower but on the same magnitude compared with that of the plasma, and sharply decreased in effluent. Conclusions: Virus DNAs in exosome samples of recipients with viral infection after transplantation were detected in great quantities.This not only hints the spread of the virus may take advantage of the biological formation process of exosomes, but also warns that the limitation of the existing way to extract exosmes from virus infected population may be a bottleneck in research.

[Anatomy research of cervical laminoplasty with preservation of the posterior ligament complex.]

Objective: To evaluate the feasibility of cervical laminoplasty with preservation of the posterior ligament complex for enlarging the spinal canal. Methods: Six up-to-standard human corpse specimens were divided into two groups by simple randomization (start from C4 group, S4; start from C5 group, S5; 3 corpses in each group). Decompression operation of C3-C6 level was performed in a predetermined sequence by using the new procedure with preservation of the posterior ligament complex.The basic depth of spinal canal was measured with a depth gauge at fixed point after the right bone groove of single level was completed.The operation of the contralateral bone groove was continued, and then the spinal canal was measured again when the spinous process was pulled backward by using a tissue forceps until the ligament complex was just tight.Retreat value (RV) of vertebral lamina was obtained by calculating the difference between the two measurements.The earlier measured levels needed to be remeasured when the operation area increased by one level. Two independent sample and one-sample t test were used to analyze the measurement results. Results: RV of vertebral lamina was small after finishing the first level of the decompression operation [S4: (0.87±0.72) mm; S5: (1.83±0.29) mm], and the value reached its maximum after the completion of C3-C6 level.The overall average RVmaxs from C3 to C6 level were (2.37±0.52) mm, (4.27±0.78) mm, (3.73±0.93) mm and (2.16±0.77) mm, respectively.The overall average retreat rates (RR) were 17%±7%, 32%±9%, 29%±10% and 16%±6%, respectively. The overall average RVmax of C4 and C5 level reached or exceeded the decompression threshold value of 4 mm (t=0.839, -0.703, both P>0.05). The average RVmax of C4/C5 level was similar in the two groups (t=-1.204, 1.189, both P>0.05); however, the difference of average RVmax between C3 and C6 level was significant (t=-4.429, 4.196, both P<0.05). Conclusions: Cervical laminoplasty with preservation of the posterior ligament complex can enlarge the sagittal diameter of spinal canal and relieve the compression of spinal cord.In addition, RV of each level increases as the number of the operation level increases, and the ability of vertebral lamina to retreat is quite different from C3 to C6 level.The decompression effect in the middle of the operation area is better than that on the cranial and tail side.

[The potential use of serum HBV RNA to guide the functional cure of chronic hepatitis B]

Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) in infected hepatocytes is the main cause of off-therapy viral rebound. The half-life of cccDNA is only 33-50 days, so the conversion of newly synthesized rcDNA to cccDNA in the nucleus is essential for the maintenance of cccDNA pool in infected hepatocytes. Though not directly targeting the existing cccDNA, current nucleos(t)ide analogues (NAs) may exhaust the cccDNA reservoir by blocking the rcDNA formation. Indeed, a prolonged consolidation therapy post loss of serum HBV DNA can achieve sustained remission and thus safe drug discontinuation in a small proportion of chronic hepatitis B (CHB) patients. In recent studies, we and others have demonstrated that it is the serum HBV RNA that reflects the cccDNA activity in infected hepatocytes, particularly among the patients on NAs. Here we suggest that instead of measuring serum HBV DNA only, simultaneous measurement of both viral DNA and RNA would improve the accuracy to reflect the cccDNA activity; therefore, the virological response should be redefined as consistent loss (less than the lower limit of detection) of both serum HBV DNA and RNA, which indicates the safety of drug discontinuation. Accumulating evidence has suggested that for the CHB patients with lower serum HBsAg, switch-to or add-on pegylated interferon (Peg-IFN) treatment would result in loss of serum HBsAg in a relatively large proportion of CHB patients. Since serum HBV RNA is an ideal biomarker to reflect the intrahepatic cccDNA activity, for the patients with a serum HBsAg level lower than 1 500 IU/ml after long-term NAs treatment, the serum HBV RNA should be measured. If serum HBV RNA is detected, peg-IFN should be added on; if serum HBV RNA is not detected, NAs treatment should be switched to peg-IFN treatment. We believe the therapy based on serum HBV RNA would make the functional cure of CHB (serum HBsAg loss or even conversion to anti-HBs) more efficient.

[Clinical and genetic characteristics of children with Leigh syndrome]

Objective: To investigate the clinically and genetic characteristics of children with Leigh syndrome. Method: Patients with clinically diagnosed Leigh syndrome(LS)in the department of Neurology, Beijing Children's Hospital from January 2013 to February 2016 underwent the mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) detecting with next generation sequencing (NGS) technology. The clinical data of gene confirmed cases were retrospectively collected and analyzed. The differences in the onset age, clinical manifestations, lactic acid level and MRI results between the mtDNA variation and nDNA variation were compared and analyzed.t test, Chi-square test and Fisher's exact test were used for statistical analysis. Result: Thirty-five cases were diagnosed by gene detection, including 20 males and 15 females. The median onset age was 1 year (ranging from the neonatal period to 4.4 years old). The age of onset within 2 years accounted for 74%(26 cases). The onset age of initial symptoms, including developmental delay, developmental regression, and seizures, were 6 (4, 12) months, 12 (8, 14) months, and 6 (1, 23) months respectively. The onset age of ptosis, extrapyramidal symptoms and ataxia were 26 (18, 44) months, 28 (23, 40) months and 28 (19, 35) months, respectively. There were significant differences in the onset age between the three groups (H=21.919, P=0.01). Within the 35 cases, 29 were manifested with developmental delay (83%), 26 with dystonia (74%), 18 with growth retardation, 15 with myasthenia, 13 with developmental regression, 11 with dysphagia, 10 with feeding difficulties, 4 with skeletal dysplasia, and 2 with digestive tract symptoms; nystagmus and respiratory abnormalities were observed in 9 cases respectively; extrapyramidal symptoms, peripheral nerve injury, ptosis, seizures were observed in 8 cases respectively; and ataxia, ophthalmoplegia and hypertrichiasis were found in 5 cases respectively.The blood lactic acid was measured in 32 LS patients, within which 23 cases (72%) had increased results; 8 out of 11 cases who underwent were cerebrospinal fluid lactic acid test had increased results. The results of neuroimaging revealed that all the patients were involved in the brainstem and (or) basal ganglia, of whom 27 (77%) had brainstem involvement, 24 (69%) had basal ganglia involvement. Thirteen out of 14 patients who had medulla oblongata involvement had nDNA variation; while 7 out of 8 patients with cerebellar involvement had nDNA variation. Genetic etiology was confirmed in all patients, among whom there were 17 cases (49%) with mtDNA mutation, including 8993T>C/G (n=5), 14487T>C (n=4), 13513G>A (n=2), 9176T>C, 10158T>C, 3697G>A, 10191T>C, 14459A>G and 11777C>A (n=1) respectively. Remaining 18 cases(51%) had nDNA mutation, including SURF1 gene(n=10), PDHA1 gene(n=3) and one case each of NDUFV1, NDUFAF6, NDUFAF5, NDUFS1 and COQ7 genes. In this study, 27 types of mutations were founded, 15 of which had not been previously reported. Respiratory chain gene mutations have been found in 31 cases(89%); 3 cases had PDHc gene mutations, and 1 case had other mutation. Conclusion: LS usually occurs in infants. The most common primary symptoms are age-dependent abnormal movements, ocular symptoms, and seizures. Respiratory chain defects is the most common causes of LS.SURF1 is the most common variation, followed by 8993T>C/G, 14487 T>C and 13513G>A mutation.

[Changes in genotype prevalence of human papillomavirus over 10-year follow-up of a cervical cancer screening cohort]

Objective: To evaluate the dynamic variation of genotypes distribution of human papillomavirus (HPV) over 10-year follow-up in a cervical cancer screening cohort. Methods: Based on the Shanxi Province Cervical Cancer Screening Study Ⅰ cohort, we detected HPV genotypes on the well-preserved exfoliated cervical cells from women who were tested HPV positive from year 2005 to year 2014 using reverse linear probe hybridization assay. The changes of prevalence of type-specific HPV over time among the overall population were estimated using linear mixed models. The association between the type-specific HPV and cervical intraepithelial neoplasia grade 2 or worse (CIN2 +) was calculated by linear Chi-square test. Finally, the trends of multiple infections of HPV with the increase of the age were analyzed. Results: During the cervical cancer screening of the overall population from 2005 to 2014, the most common genotypes among the population were HPV16 and 52. The prevalence of HPV16 decreased over time from 4.6% in 2005 to 2.2% in 2010 and 2014 (F=8.125, P<0.001). The prevalence of HPV52 remained pretty stable and HPV33, 51 and 58 slightly decreased then apparently increased. Further stratification analysis by pathological lesions showed the same trend of the HPV prevalence for the histology normal women with the overall population. Of note, for those women with the cervical intraepithelial neoplasia (CIN2 +), the detection rate of HPV16 decreased from 65.22% in 2005 to 41.03% in 2010 and finally to 31.58% in 2014 (χ(2)=4.420, P=0.036) and that of HPV33 substantially increased. No significant variation was found for other types of HPV. Multiple infection rate varied with the growing age of the women. Conclusions: The genotypes prevalence of HPV tended to vary over time during cervical cancer screening in the context of regular screening combining with immediate treatment for those CIN2 + women. HPV16 prevalence significantly decreased over time, which indicated that the variation of type-specific HPV prevalence should be considered when regular cervical cancer screening was organized using HPV technique.

[Research of mHLA-G and the receptor expression with kidney rejection and CMV active infection following kidney transplantation]

Objective: To study the expression of membrane HLA-G (mHLA-G) and the receptor immunoglobulin-like transcript 2(ILT2) on lymphocyte and find their association with rejection and cytomegalovirus (CMV) infection after renal transplantation. Methods: A total of 88 cases of renal transplant recipients for the first time from February 2014 to February 2016 were studied in this work. Recipients can be divided into rejection group (n=12) and stable renal function group (n=41) according to whether rejection occurred. Recipients only infected CMV not developed rejection were included in the CMV positive group (n=24). CMV negative group (n=11) including CMV negative recipients once infected CMV.The expression of mHLA-G and ILT2 on lymphocytes were detected by flow cytometry, and the differences among different groups were analyzed. Results: The data showed that after renal transplantation, T and B lymphocytes mHLA-G expression rate was the lowest in the rejection group (0.42%±0.35%, 0.88%±0.47%), having significant difference with renal function stable group and CMV positive group (all P<0.01). In CMV positive group the expression of mHLA-G on T and B lymphocytes was the highest (1.31%±0.69%, 2.01%±0.91%), having significant difference with rejection group (P<0.001). The expression of mHLA-G on B cell was statistically significantly different between CMV positive group and CMV negative group (P<0.05). There was no significant difference in ILT2 expression on B cell among the four groups (P>0.05). The expression rate of ILT2 on T cells was higher in the CMV positive group (36.91%±14.91%), having significant difference with the other three groups (P<0.01). Conclusions: Low expression of mHLA-G on T and B lymphocytes may predict rejection after renal transplantation. High expression of mHLA-G and ILT2 on lymphocytes is prone to CMV infection after renal transplantation .

[A review of progress in research of effect of air pollutants on fetal growth]

Slow fetal growth is a global public health concern because it might be associated with many diseases later in life. With the progress of technology to measure long-term air pollution exposure. Many epidemiological studies have evaluated the effects of maternal air pollutant exposure on fetal growth. In this paper, we summarize the research progress in this field after the analysis on the related literatures retrieved from the databases of Medline and Web of Science.

[Prospective evaluation on ventilator-associated events: a cohort study from eight intensive care units]

OBJECTIVE

The aim of this study was to prospectively investigate the incidence of ventilator associated events (VAEs) in intensive care units (ICUs) among adult patients, and to evaluate the correlation between VAEs and ventilator associated pneumonia (VAP).

METHODS

A prospective 3-month cohort study (January 2015 to March 2015) was carried out. VAEs were divided into three groups: with ventilator-associated condition (VAC), with infection related ventilator-associated complication (IVAC) and with possible VAP (PVAP). Sensitivity and specificity of VAEs were evaluated and compared to the traditional VAP. Kappa test was applied to judge the consistency of VAC and VAP.

RESULTS

During Jan. 2015 and Mar. 2015, 1 014 patients were admitted to 8 ICUs, with 7 977 patients per day. In total, 197 patients used the mechanical ventilation installation, with, a total number of 3 152 ventilator-days. Finally, 1 214 ventilation days in the VAC group and 1 938 ventilation days in the non-VAC group) that were available for final analysis. 46 VAC cases were identified including 22 classified as IVAC (14.59 and 6.98 per 1 000 ventilation days, respectively). Length of ICU stay and duration on mechanical ventilation for VAC patients were both significantly longer than those for non-VAC patients (P<0.05). Sensitivity and specificity of the VAC criteria for the detection of VAP were 36.92% and 83.33%, respectively.

CONCLUSION

The VAEs surveillance paradigms could be applied to monitor patients on the use of mechanical ventilation installation. However, sensitivity and specificity of VAC were under pool for the diagnosis of VAP. However, automatically surveillance programs was relied on the improvement of auto-information systems.

Hydronephrosis caused by intrauterine contraceptive device migration: three case reports with literature review

Translocation of intrauterine contraceptive device (IUD) from the uterus rarely occurs, which can lead to serious complications. Here the authors reported three cases of IUD migration from into the ureter, bladder, and peritoneal cavity that caused hydronephrosis, respectively. All the three patients received minimally invasive surgeries and recovered.

[Clinical and electroencephalographic analysis of anti-N-methyl-D-aspartate receptor encephalitis in children]

OBJECTIVE

To study the clinical and electroencephalographic (EEG) characteristics of anti-N-methyl-D-aspartate receptor encephalitis (anti-NMDAR encephalitis) in children.

METHOD

Retrospective analysis was performed on the clinical and EEG data of 105 patients with anti-NMDAR encephalitis treated in Beijing Children's Hospital (August 2011-March 2015). Of the 105 patients, 38 were male and 67 were female.The age of onset was from 6 months and 26 days to 15 years and 8 months (average (8±4)years). The time for confirmed diagnosis was from 4 days to 850 days (median 24.5 days). According to the modified Rankin scales, the patient's clinical conditions were assessed and underwent continuous EEG (cEEG) monitoring.The data were reviewed and analyzed.

RESULT

Based on the severity of the disease, the 105 patients were divided into three groups: mild group (12 cases), moderate group (65 cases), and severe group (28 cases). There were 91 cases(86.7%)with abnormal EEG patterns, including 28 cases (26.7%) with slow background activity in EEG, 25 cases (23.8%) with generalized or diffuse slow waves, 33 cases (31.4%) had focal slow waves, 41 cases (39.0%) had epileptic waves; 10 cases (9.5%) showed unilateral or diffuse alpha-theta band rhythms in nonrapid eye movement (NREM) sleep, 7 cases (6.7%) showed extreme delta brush waves (EDB). Accordingly, the number of patients with abnormal EEG in mild, moderate and severe groups was 5, 58 (89.2%) and 28(100.0%). Seven patients with EDB phenomenon were all in the severe group, and 10 patients with abnormal alpha-theta band rhythms were in the moderate group.

CONCLUSION

In children with anti-NMDAR encephalitis, the EEG patterns are in line with the changes of EEG in general encephalitis.The extent of EEG abnormalities correlates with the clinical severity of the disease. Extreme delta brush and alpha-theta band rhythms may be suggestive of diagnosis and clinical assessment of the disease.

Gastric Metastasis of Hepatocellular Carcinoma With Gastrointestinal Bleeding After Liver Transplant: A Case Report

Gastrointestinal (GI) metastasis of hepatocellular carcinoma is very rare. This is the first report of post-transplantation gastric metastasis. A 43-year-old man with a history of hepatitis B-related hepatocellular carcinoma (HCC) in the right anterior segment of the liver received an orthotopic liver transplant. Three months after the transplantation, pulmonary metastasis was found by chest computed tomography, and he received 1 course of gamma knife treatment. He complained of melena with anemia 17 months post liver transplantation. Abdominal CT scan showed new occupying lesions in the liver and a mass in the stomach and around the spleen with embolus in the splenic vein. Endoscopy revealed a large irregular cauliflower-like mass in fundus with ulceration and bleeding on the surface. He received symptomatic treatment, but died of cancer-related bleeding 4 months later. GI bleeding may due to gastric metastasis after liver transplantation.

[Polyp within massive concha bullosa: a case report]

To discuss the complication of common anatomic variant of the middle turbinate-concha bullosa. We present a 63 years old man with nasal obstruction who was diagnosed to be a polyp originated from concha bullosa by CT and operation. Polyp originated from middle meatus was squeezed into concha bullosa. Endoscopic operation is the best treatment to this disesase. Concha bullosa can result in obstruction of middle meatus and then lead to sinusitis. This case, polyp originated from middle meatus was squeezed into concha bullosa, it was a rare occurrence.

Ultrafast Dynamics Evidence of High Temperature Superconductivity in Single Unit Cell FeSe on SrTiO_{3}

We report the time-resolved excited state ultrafast dynamics of single unit cell (1 UC) thick FeSe films on SrTiO_{3} (STO), with FeTe capping layers. By measuring the photoexcited quasiparticles' density and lifetime, we unambiguously identify a superconducting (SC) phase transition, with a transition temperature T_{c} of 68 (-5/+2)  K and a SC gap of Δ(0)=20.2±1.5  meV. The obtained electron-phonon coupling strength λ is as large as 0.48, demonstrating the likely crucial role of electron-phonon coupling in the high temperature superconductivity of the 1 UC FeSe on STO systems. We further find a 0.05 THz coherent acoustic phonon branch in the capping layer, which provides an additional decay channel to the gluing bosons.

Effects of Surface Electron Doping and Substrate on the Superconductivity of Epitaxial FeSe Films

Superconductivity in FeSe is greatly enhanced in films grown on SrTiO3 substrates, although the mechanism behind remains unclear. Recently, surface potassium (K) doping has also proven able to enhance the superconductivity of FeSe. Here, by using scanning tunneling microscopy, we compare the K doping dependence of the superconductivity in FeSe films grown on two substrates: SrTiO3 (001) and graphitized SiC (0001). For thick films (20 unit cells (UC)), the optimized superconducting (SC) gaps are of similar size (∼9 meV) regardless of the substrate. However, when the thickness is reduced to a few UC, the optimized SC gap is increased up to ∼15 meV for films on SrTiO3, whereas it remains unchanged for films on SiC. This clearly indicates that the FeSe/SrTiO3 interface can further enhance the superconductivity, beyond merely doping electrons. Intriguingly, we found that this interface enhancement decays exponentially as the thickness increases, with a decay length of 2.4 UC, which is much shorter than the length scale for relaxation of the lattice strain, pointing to interfacial electron-phonon coupling as the likely origin.